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WorksheetsNeuro Week #9
Total questions: 149
Worksheet time: 5hrs 58mins
What is the primary function of the retina and what are the specialized cells that enable the retina to perform this function?
- Outermost layer, the motor of the eye.
- It contains photoreceptor cells, rods, and cones, that reflect light energy into electrical signals sent to the eye.
- Innermost layer, the sensory of the eye.
- It contains photoreceptor cells, rods, and cones, that transduce light energy into electrical signals sent to the brain.
What are the three specialized regions of the retina and their corresponding function?
Fovea, Macula & Optic Disc
Cornea, Iris & Optic Disc
Fovea, Cornea & Optic Disc
Iris, Macula & Cornea
What is the function of fovea?
the head of the optic nerve which has no photoreceptors creating a blind spot in the visual field.
surround the fovea and is important for central visual acuity.
the area of highest visual acuity and is important for sharp central vision.
What is the function of macula?
the head of the optic nerve which has no photoreceptors creating a blind spot in the visual field.
surround the fovea and is important for central visual acuity.
the area of highest visual acuity and is important for sharp central vision.
What is the function of the optic disc?
the area of highest visual acuity and is important for sharp central vision.
surround the fovea and is important for central visual acuity.
the head of the optic nerve which has no photoreceptors creating a blind spot in the visual field.
What is the function of the ciliary body?
Can adjust the speed and the reflexion of the cornea and the iris, which can adjust the aperture of the fovea.
Can adjust the shape and the refraction of the lens and the iris, which can adjust the aperture of the pupil.
How is coordination of the two eyes accomplished?
Synergistic action of extraocular muscles
Antagonism action of extraocular muscles
Synergistic action of intraocular muscles
What happens to light as it travels through the cornea?
As light travels through the cornea it is refracted or bent resulting in the projection of the central fields onto the retina to be same and right side out.
As light travels through the cornea it is refracted or bent resulting in the projection of the visual fields onto the retina to be reversed and inverted.
As light travels through the cornea it is refracted or straight resulting in the projection of the central fields onto the retina to be reversed and right side up.
Why is the precise control of eye position vital for vision?
- Is vital for vision because the best visual acuity is available only in a small region of the retina, the fovea, and because binocular perception of an object as a single object requires that the image be viewed by corresponding points on both retinas.
- Is vital for vision because the best visual acuity is available only in a large region of the retina, the fovea, and because monocular perception of an object as a single object requires that the image be viewed by corresponding points on only one of the retinas.
What happens as light crosses through the aperture of the iris?
- Adjusts the amount of light that rise on the retina by adjusting the height of the cornea.
- Adjusts the amount of light that rise on the retina by adjusting the thinness of the pupil.
- Adjusts the amount of light that falls on the retina by adjusting the diameter of the pupil.
What is the first projection neuron in the visual pathway?
- Retinal output cell is the first projection neuron in the visual pathway to the visual cortex and conveys signals to the thalamus.
- Retinal input cell is the first projection neuron in the visual pathway to the cerebral cortex and conveys signals to the amygdala.
- Retinal input cell is the first projection neuron in the visual pathway to the visual cortex and conveys signals to the brainstem.
Which cranial nerve conveys visual information from the retina to the optic chiasm?
Abducens Nerve (VI)
Oculomotor Nerve (III)
Optic Nerve (II)
Trochlear Nerve (IV)
Where does information from the nasal half of each retina project to?
- Info from the nasal half of each retina crosses the midline in the optic chiasm and projects to the contralateral visual cortex.
- Info from the nasal half of each retina continues ipsilaterally through the optic chiasm and projects to the ipsilateral cortex.
Where does information from the temporal half of each retinal project to?
- Info from the temporal half of each retina continues ipsilaterally through the optic chiasm and projects to the ipsilateral cortex.
- Info from the temporal half of each retina crosses the midline in the optic chiasm and projects to the contralateral visual cortex.
What happens at the optic chiasm and what functional purpose does this serve?
- Outcome of the axon arrangement in the chiasm is that motor info from one motor field either the right or left is delivered to the same side of the motor cortex.
- Light from the left visual field strikes the right half of the left and right retinas.
- Outcome of the axon arrangement in the chiasm is that visual info from one visual field either the right or left is delivered to the opposite visual cortex.
- Light from the right visual field strikes the left half of the right and left retinas.
What is the second neuron in the visual pathway which relays visual information to the primary visual cortex that the axons in the optic tract synapse with?
Inhibitory neurons
Postsynaptic neurons
Sensory neurons
Interneurons
What is the tract called that relays visual information from the lateral geniculate to the primary visual cortex?
Geniculocalcarine tract
Corticospinal Tract
Corticobulbar Tract
Rubrospinal Tract
What does the primary visual cortex do with the visual information it receives?
Analyze color and motion.
Discriminate the shape, size, or texture of objects.
Used for orientation and eye movement control.
What does the secondary visual cortex do with the visual information it receives?
Discriminate the shape, size, or texture of objects.
Analyzed color and motion.
Used for orientation and eye movement control.
What is the stream of visual information that flows dorsally via the posterior parietal cortex used for?
Called the perception stream because this info is used to recognize visual objects.
Called the action stream because this information is used to direct movement.
What is the stream of visual information that flows ventrally used for?
Called the action stream because this information is used to direct movement.
Called the perception stream because this info is used to recognize visual objects.
What is the visual information transmitted to the superior colliculus in the midbrain used for?
Discriminate the shape, size, or texture of objects.
Used for orientation and eye movement control.
Analyzed color and motion.
What is the visual information transmitted to the pretectal area in the midbrain used for?
Produce corneal reflexes.
Produce pupillary reflexes.
Oculocephalic reflexes.
Vestibulo-ocular reflexes.
Which cranial nerve provides parasympathetic efferents for the pupillary light reflex and the near triad?
Oculomotor nerve
Olfactory nerve
Abducens nerve
Which intrinsic muscles of the eye does the oculomotor nerve innervate?
Superior rectus & inferior oblique.
Ciliary muscle & sphincter pupillae.
Lateral rectus & inferior rectus.
Medial rectus & sphincter pupillae.
What is the function of the ciliary muscle?
accommodation for the distance of an object, provides focus on near vision by decreasing tension of ligaments that hold the lens in place & this increases the natural curvature of the lens.
constricts the pupil.
What is the function of the sphincter pupillae?
accommodation for the distance of an object, provides focus on near vision by decreasing tension of ligaments that hold the lens in place & this increases the natural curvature of the lens.
constricts the pupil.
What are the purposes of the pupillary light reflex?
When light is shined in one eye, pupil decompression occurs in the eye directly stimulated by dim light.
When light is shined in one eye, pupil constriction occurs in the eye directly stimulated by bright light.
What is the pathway sequence for the pupillary light reflex and consensual light reflex?
Light reaches the cornea and information travels via the oculomotor nerve and tract to the pretectal nuclei in the cerebral cortex. Fibers form each pretectal nucleus send unilateral projections to the Edinger-Westphal nuclei which is the sympathetic nuclei of the optic nerve.
Light reaches the retina and information travels via the optic nerve and tract to the pretectal nuclei in the midbrain. Fibers form each pretectal nucleus send bilateral projections to the Edinger-Westphal nuclei which is the parasympathetic nuclei of the oculomotor nerve.
What is the purpose of the accommodation reflex?
Occurs when focusing on a near object in order to achieve a clear, precise projection onto the fovea of the retina.
Occurs when focusing on a far away object in order to achieve a clear, precise projection onto the macula of the retina.
Occurs when focusing on a up close object in order to achieve a clear, precise projection onto the optic disc of the retina.
What are the three actions (near triad) that adjust the eyes during the accommodation reflex?
- Convergence of the eyes repositions the eyes to aim at the object maintaining singular monocular vision of the object.
- The straightness of the lens changes to decrease refractive power.
- The pupil narrows to sharpen the image by decreasing the depth of focus.
- Convergence of the eyes repositions the eyes to aim at the object maintaining singular binocular vision of the object.
- The curvature of the lens changes to increase refractive power.
- The pupil constricts to sharpen the image by increasing the depth of focus.
Which muscles does the trochlear nerve innervate and what movements do they produce?
- Lateral rectus muscle
- Moves the eye laterally.
- Superior oblique muscle
- Rotates the eye around the axis of the pupil or, if the eye is adducted, depresses the eye.
Which muscles does the abducens nerve innervate and what movements do they produce?
- Superior oblique muscle
- Rotates the eye around the axis of the pupil or, if the eye is adducted, depresses the eye.
- Lateral rectus muscle
- Moves the eye laterally.
What is the role of the medial longitudinal fasciculus in the eye movement system?
A brainstem tract, that conveys a signal from the left abducens nucleus to the right optic nucleus.
A brainstem tract, that conveys a signal from the right abducens nucleus to the left oculomotor nucleus.
A brainstem tract, that conveys a signal from the left abducens nucleus to the right oculomotor nucleus.
What are the two goals of eye movements?
- Keeping position of the eyes stable during head movements so that the environment does not appear to bounce and directing the gaze at visual targets.
- Keeping position of the eyes unstable during limb movements so that the environment does appear to bounce and indirecting the gaze at motor targets.
What are conjugate eye movements?
- Both eyes move in the same direction.
- The eyes move toward the midline or away from the midline.
What are vergence eye movements?
- Both eyes move in the same direction.
- The eyes move toward the midline or away from the midline.
How is gaze stabilization achieved during head movements?
- Achieved by the pupillary reflex or the VOR and optokinetic nystagmus.
- Achieved by the vestibulocular reflex or the VOR and optokinetic nystagmus.
- Achieved by the vestibulocular reflex or the VOR and jerk nystagmus.
- Achieved by the pupillary reflex or the VOR and pendular nystagmus.
What is the vestibulo-ocular reflex?
- The action of vestibular info on eye position during slow movements of the head.
- The action of vestibular info on eye position during fast movements of the head.
What is optokinetic nystagmus?
- Is the use of visual information to stabilize images during fast movements of the head or when visual objects are moving relative to the trunk.
- Is the use of motor information to stabilize images during fast movements of the head or when visual objects are moving relative to the limbs.
- Is the use of visual information to stabilize images during slow movements of the head or when visual objects are moving relative to the head.
How is the direction of gaze achieved?
- Accomplished by vestibular receptors, smooth pursuits, and vergence movements.
- Accomplished by saccades, smooth pursuits, and vergence movements.
- Accomplished by conjugate, VOR, and vergence movements.
What are saccades?
Eye movements that stop when following a moving object.
Fast eye movements used to switch gaze from one object to another which bring new objects into central vison, where details of images are seen.
Eye movements that follow a moving object.
What are smooth pursuit eye movements?
Fast eye movements used to switch gaze from one object to another which bring new objects into central vison, where details of images are seen.
Eye movements that stop when following a moving object.
Eye movements that follow a moving object.
What planes can gaze occur in?
Vertical plane, looking left or right or in a horizontal plane, looking up or down.
Horizontal plane, looking left or right or in a vertical plane, looking up or down.
Sagittal plane, looking left or right or in a frontal plane, looking up or down.
Anterior plane, looking left or right or in a posterior plane, looking up or down.
What are the two gaze centers?
Anterior & Posterior
Vertical & Horizontal
Sagittal & Frontal
Where is the vertical gaze center located?
located in the midbrain, specifically the midbrain reticular formation.
located in the pons, specifically in the paramedian pontine reticular formation.
Where is the horizontal gaze center located?
located in the pons, specifically in the paramedian pontine reticular formation.
located in the midbrain, specifically the midbrain reticular formation.
Where are the vestibular receptors for the VOR located?
In the cerebral cortex
In three fluid filled tubes inside the inner ear, called semicircular canals.
In the vestibular nuclei
In the fovea
Where does the sensory information from the semicircular canals relayed to for coordination of visual stabilization?
Substantia nigra
Solitary nucleus
Vestibular nuclei
Motor efferent nuclei
When is it important for the VOR to be suppressed?
- Sometimes when a person turns the head, the intent is to look in the new direction rather than have the eyes fixate on the previous target. To accomplish this, suppression of the VOR is essential.
- Sometimes when a person puts the head down, the intent is to look in the opposite direction rather than have the eyes fixate on the current target. To accomplish this, suppression of the VOR is essential.
Which eye muscles are activated when the face tilts down?
- Ipsilateral superior rectus and the contralateral inferior oblique.
- Ipsilateral medial rectus & contralateral lateral rectus.
- Ipsilateral superior oblique & contralateral inferior rectus.
Which eye muscles are activated when the face turns right or left?
- Ipsilateral superior rectus and the contralateral inferior oblique.
- Ipsilateral superior oblique & contralateral inferior rectus.
- Ipsilateral medial rectus & contralateral lateral rectus.
Which eye muscles are activated when the face tilts up?
- Ipsilateral superior rectus and the contralateral inferior oblique.
- Ipsilateral superior oblique & contralateral inferior rectus.
- Ipsilateral medial rectus & contralateral lateral rectus.
When is an optokinetic nystagmus response elicited?
- When the head is unstable & the environment is not moving.
- When the environment is stable & the head is moving.
- When the head is stable & the environment is moving.
What is physiologic nystagmus and how can it be elicited?
- Normal response that can be elicited in an intact nervous system by sympathetic stimulation, turning of the head, visual stimulation of the semicircular canals, or by moving the eyes to the low horizontal position.
- Normal response that can be elicited in an intact nervous system by optokinetic stimulation, rotation of the head, temperature stimulation of the semicircular canals, or by moving the eyes to the extreme horizontal position.
How is the direction of nystagmus named?
- According to the direction of vergence eye movements.
- According to the direction of smooth pursuit eye movements.
- According to the direction of saccadic eye movements.
- According to the direction of vestibulo-ocular eye movements.
Which structures, type of sensory information, and reflexes can influence eye movements?
- Auditory info via the superior colliculus, the VOR, visual stimuli, sensory info from extraocular muscles, and the emotion system.
- Visual info via the inferior colliculus, the VOR, auditory stimuli, motor info from intraocular muscles, and the emotion system.
What is disconjugate gaze and what role does it serve in the eye movement system?
- Refers to movement of the eyes in opposite directions.
- Critical for our ability to focus on objects of varying distance.
- Refers to movement of the eyes in same directions.
- Critical for our ability to focus on objects of close up distance.
What happens with convergence eye movements?
- Focus on objects that are closer to us via both eyes converging or looking medially. When both of the medial rectus muscles contract turning the eyes towards the midline or adducting the eyes.
- Divergence occurs when both of the lateral rectus muscles contract, which turn the eyes away from midline or abduct the eyes.
What happens with divergence eye movements?
- Focus on objects that are closer to us via both eyes converging or looking medially. When both of the medial rectus muscles contract turning the eyes towards the midline or adducting the eyes.
- Divergence occurs when both of the lateral rectus muscles contract, which turn the eyes away from midline or abduct the eyes.
What is the purpose, type of movement and origin of command for VOR rapid?
- Purpose: to maintain the gaze on a moving target.
- Type of Movement: voluntary conjugate
- Origin of Command: visual cortex
- Purpose: to keep the gaze fixed on a target during slow, sustained head movements.
- Type of Movement: reflex conjugate
- Origin of Command: visual cortex
- Purpose: to keep the gaze fixed on a target.
- Type of Movement: reflex conjugate
- Origin of Command: vestibular nuclei
- Purpose: to rapidly move the eyes to a new target.
- Type of Movement: voluntary or reflexive conjugate.
- Origin of Command: frontal eye fields
What is the purpose, type of movement and origin of command for optokinetic?
- Purpose: to maintain the gaze on a moving target.
- Type of Movement: voluntary conjugate
- Origin of Command: visual cortex
- Purpose: to keep the gaze fixed on a target during slow, sustained head movements.
- Type of Movement: reflex conjugate
- Origin of Command: visual cortex
- Purpose: to rapidly move the eyes to a new target.
- Type of Movement: voluntary or reflexive conjugate.
- Origin of Command: frontal eye fields
- Purpose: to align the eyes on a near target.
- Type of Movement: voluntary deconjugate.
- Origin of Command: visual cortex
What is the purpose, type of movement and origin of command for smooth pursuit?
- Purpose: to rapidly move the eyes to a new target.
- Type of Movement: voluntary or reflexive conjugate.
- Origin of Command: frontal eye fields
- Purpose: to align the eyes on a near target.
- Type of Movement: voluntary deconjugate.
- Origin of Command: visual cortex
- Purpose: to maintain the gaze on a moving target.
- Type of Movement: voluntary conjugate
- Origin of Command: visual cortex
- Purpose: to keep the gaze fixed on a target.
- Type of Movement: reflex conjugate
- Origin of Command: vestibular nuclei
What is the purpose, type of movement and origin of command for saccadic?
- Purpose: to rapidly move the eyes to a new target.
- Type of Movement: voluntary or reflexive conjugate.
- Origin of Command: frontal eye fields
- Purpose: to align the eyes on a near target.
- Type of Movement: voluntary deconjugate.
- Origin of Command: visual cortex
- Purpose: to keep the gaze fixed on a target during slow, sustained head movements.
- Type of Movement: reflex conjugate
- Origin of Command: visual cortex
- Purpose: to keep the gaze fixed on a target.
- Type of Movement: reflex conjugate
- Origin of Command: vestibular nuclei
What is the purpose, type of movement and origin of command for vergence?
- Purpose: to keep the gaze fixed on a target during slow, sustained head movements.
- Type of Movement: reflex conjugate
- Origin of Command: visual cortex
- Purpose: to maintain the gaze on a moving target.
- Type of Movement: voluntary conjugate
- Origin of Command: visual cortex
- Purpose: to rapidly move the eyes to a new target.
- Type of Movement: voluntary or reflexive conjugate.
- Origin of Command: frontal eye fields
- Purpose: to align the eyes on a near target.
- Type of Movement: voluntary deconjugate.
- Origin of Command: visual cortex
What are the primary structures and their function in the outer ear?
- Composed of a bony labyrinth that contains three semicircular canals and the vestibule specialized for vestibular function or balance and the cochlea for hearing.
- Transforms vibrating sound waves into electrical signals that travel along the cochlear nerve to the brain.
- Is a chamber filled with air that contains a series of small bones or ossicles that efficiently transmits sound waves from the tympanic membrane to the fluid-filled inner ear.
- The ossicles in the middle ear are the malleus, the incus, and the stapes.
- Composed of the auricle and the external auditory meatus
- Collect sound waves and focus them on the tympanic membrane, which is located at the medial end of the outer ear canal.
What are the primary structures and their function in the middle ear?
- Is a chamber filled with air that contains a series of small bones or ossicles that efficiently transmits sound waves from the tympanic membrane to the fluid-filled inner ear.
- The ossicles in the middle ear are the malleus, the incus, and the stapes.
- Composed of a bony labyrinth that contains three semicircular canals and the vestibule specialized for vestibular function or balance and the cochlea for hearing.
- Transforms vibrating sound waves into electrical signals that travel along the cochlear nerve to the brain.
- Composed of the auricle and the external auditory meatus
- Collect sound waves and focus them on the tympanic membrane, which is located at the medial end of the outer ear canal.
What are the primary structures and their function in the inner ear (for hearing)?
- Is a chamber filled with air that contains a series of small bones or ossicles that efficiently transmits sound waves from the tympanic membrane to the fluid-filled inner ear.
- The ossicles in the middle ear are the malleus, the incus, and the stapes.
- Composed of a bony labyrinth that contains three semicircular canals and the vestibule specialized for vestibular function or balance and the cochlea for hearing.
- Transforms vibrating sound waves into electrical signals that travel along the cochlear nerve to the brain.
- Composed of the auricle and the external auditory meatus
- Collect sound waves and focus them on the tympanic membrane, which is located at the medial end of the outer ear canal.
How is sound converted into neural signals?
- Sound waves strike semicircular canals.
- Ossicles move, causing vibrations of membrane at opening of lower chamber.
- Movement of fluid in lower chamber.
- Vibration of vestibular membrane & attached hair cells.
- Hairs bend because the ends are embedded in the immobile tectorial membrane. Hair cells polarize.
- Cochlear nerve endings deactivated.
- Sound waves strike eardrum.
- Ossicles move, causing vibration of membrane at opening of upper chamber.
- Movement of fluid in upper chamber.
- Vibration of basilar membrane & attached hair cells.
- Hairs bend because the tips are embedded in the immobile tectorial membrane. Hair cells depolarize.
- Cochlear nerve endings activated.
What are the three basic functions of auditory information?
- Orients the head and eyes away from sounds, decreases the activity level throughout the central nervous system, and provides unconscious awareness and recognition of sounds.
- Orients the head and eyes toward sounds, increases the activity level throughout the central nervous system, and provides conscious awareness and recognition of sounds.
Where are the signals from the cochlear nerve first processed?
Lateral lemniscus nuclei
Superior olivary nuclei
Cochlear nuclei
Auditory nuclei
What does the reticular formation use auditory information for?
Integrates auditory info from both ears to detect the location of sounds.
Activating effect of sounds on the entire central nervous system, such as loud sounds wakening a person from sleep.
Serves as a thalamic relay station for auditory info to the primary auditory cortex, where sounds reach conscious awareness.
What does the inferior colliculus do with the auditory information it receives?
Integrates auditory info from both ears to detect the location of sounds.
Serves as a thalamic relay station for auditory info to the primary auditory cortex, where sounds reach conscious awareness.
Activating effect of sounds on the entire central nervous system, such as loud sounds wakening a person from sleep.
What does the medial geniculate body do with the auditory information it receives?
Activating effect of sounds on the entire central nervous system, such as loud sounds wakening a person from sleep.
Serves as a thalamic relay station for auditory info to the primary auditory cortex, where sounds reach conscious awareness.
Activating effect of sounds on the entire central nervous system, such as loud sounds wakening a person from sleep.
What are the three cortical areas that process auditory and what are their functions?
- Primary auditory cortex: site of conscious awareness of the intensity of sounds
- An Adjacent cortical area, the secondary auditory cortex, compares sounds with memories of other sounds, and then categorizes the sounds as language, music, or noise.
- Comprehension of spoken language occurs in Wernicke’s area.
- Secondary auditory cortex: site of unconscious awareness of the intensity of vibrations
- An Adjacent cortical area, the primary auditory cortex, compares vibrations with memories of other sounds, and then categorizes the sounds as language, music, or noise.
- Comprehension of spoken language occurs in Broca’s area.
What are the symptoms and signs of a complete lesion of the optic nerve?
- Contralateral blindness and gain of the direct pupillary light reflex.
- Ipsilateral blindness and loss of the direct pupillary light reflex.
- Contralateral blindness and loss of the direct pupillary light reflex.
Where are the lesions located that causes anopia and what type of visual field deficit occurs?
- Damage to fibers in the center of the optic chiasm interrupting the axons from the nasal half of each retina.
- Loss of info in both temporal visual fields.
- Optic nerve lesion, causes loss of vision from the right eye.
- Lesions occurring behind the optic chiasm (optic tracts, LGN, optic radiations or visual cortex).
- Loss of visual info from the same visual field, right or left, in both eyes.
- Incomplete optic tract lesion (posterior to the optic chiasm)
- Partial loss of vision from the contralateral visual field.
Where are the lesions located that causes bitemporal hemianopia and what type of visual field deficit occurs?
- Optic nerve lesion, causes loss of vision from the right eye.
- Damage to fibers in the center of the optic chiasm interrupting the axons from the nasal half of each retina.
- Loss of info in both temporal visual fields.
- Lesions occurring behind the optic chiasm (optic tracts, LGN, optic radiations or visual cortex).
- Loss of visual info from the same visual field, right or left, in both eyes.
- Incomplete optic tract lesion (posterior to the optic chiasm)
- Partial loss of vision from the contralateral visual field.
Where are the lesions located that causes homonymous hemianopia and what type of visual field deficit occurs?
- Incomplete optic tract lesion (posterior to the optic chiasm)
- Partial loss of vision from the contralateral visual field.
- Lesions occurring behind the optic chiasm (optic tracts, LGN, optic radiations or visual cortex).
- Loss of visual info from the same visual field, right or left, in both eyes.
- Damage to fibers in the center of the optic chiasm interrupting the axons from the nasal half of each retina.
- Loss of info in both temporal visual fields.
- Optic nerve lesion, causes loss of vision from the right eye.
Where are the lesions located that causes quadrantanopia and what type of visual field deficit occurs?
- Optic nerve lesion, causes loss of vison from the right eye.
- Damage to fibers in the center of the optic chiasm interrupting the axons from the nasal half of each retina.
- Loss of info in both temporal visual fields.
- Lesions occurring behind the optic chiasm (optic tracts, LGN, optic radiations or visual cortex).
- Loss of visual info from the same visual field, right or left, in both eyes.
- Incomplete optic tract lesion (posterior to the optic chiasm)
- Partial loss of vision from the contralateral visual field.
What are the visual symptoms that can occur with a pituitary gland tumor due to compression of the optic chiasm and/or the cavernous sinus?
- Homonymous hemianopia, the loss of both parietal visual fields, because the axons cross in the midline directly above the pituitary gland.
- Bitemporal hemianopia, the loss of both temporal visual fields, because the axons cross in the optic chiasm directly above the pituitary gland.
- Quadrantanopia, the loss of both temporal visual fields, because the axons cross in the optic chiasm directly above the pituitary gland.
Which cranial nerves may be compressed due to compression of the cavernous sinus?
- Cranial Nerves II, V or X.
- Cranial Nerves III, IV or VI.
- Cranial Nerves II, IV or VII.
What are the other symptoms of a pituitary tumor?
- Misalignment of the eyes. If the disorder is acute, double vision will occur because images of objects will not coincide on the retinas.
- Due to hyposecretion or hypersecretion include headaches, nausea and vomiting, irregular menses and lactation, and sexual dysfunction. High blood pressure, an increased blood glucose level, acromegaly, or Cushing's disease can also occur.
- Ipsilateral ptosis, ipsilateral eye positioned down and out, diplopia, decreased ability to move the ipsilateral eye medially, downward, and upward, loss of ipsilateral direct pupillary light reflex, and loss of constriction of the pupil in response to focusing on a near object.
What is cortical blindness?
- Bilateral loss of visual cortex function, no awareness of any visual info due to a lesion in the brain, bilateral lesions of the primary visual cortex.
- The ability of a person with cortical blindness to orient to, point to, or detect movements of visual objects or even distinguish facial expressions despite the inability to consciously see objects.
What is blindsight?
- Bilateral loss of visual cortex function, no awareness of any visual info due to a lesion in the brain, bilateral lesions of the primary visual cortex.
- The ability of a person with cortical blindness to orient to, point to, or detect movements of visual objects or even distinguish facial expressions despite the inability to consciously see objects.
In general, what symptoms and signs can occur with lesions that affect the cranial nerves that innervate extraocular muscles?
- Misalignment of the eyes. If the disorder is acute, double vision will occur because images of objects will not coincide on the retinas.
- Ipsilateral ptosis, ipsilateral eye positioned down and out, diplopia, decreased ability to move the ipsilateral eye medially, downward, and upward, loss of ipsilateral direct pupillary light reflex, and loss of constriction of the pupil in response to focusing on a near object.
- Prevents activation of the superior oblique muscle, Ipsilateral eye is elevated, inability of ipsilateral eye to look downward when ipsilateral eye is adducted, double vision, difficulty reading, and visual problems when descending stairs.
What are the symptoms and signs of a complete lesion of the oculomotor nerve?
- Prevents activation of the superior oblique muscle, Ipsilateral eye is elevated, inability of ipsilateral eye to look downward when ipsilateral eye is adducted, double vision, difficulty reading, and visual problems when descending stairs.
- Ipsilateral ptosis, ipsilateral eye positioned down and out, diplopia, decreased ability to move the ipsilateral eye medially, downward, and upward, loss of ipsilateral direct pupillary light reflex, and loss of constriction of the pupil in response to focusing on a near object.
- Misalignment of the eyes. If the disorder is acute, double vision will occur because images of objects will not coincide on the retinas.
What are the symptoms and signs of a complete lesion of the trochlear nerve?
- Ipsilateral eye to deviate inward, inability to voluntarily abduct the ipsilateral eye & diplopia.
- Prevents activation of the superior oblique muscle, Ipsilateral eye is elevated, inability of ipsilateral eye to look downward when ipsilateral eye is adducted, double vision, difficulty reading, and visual problems when descending stairs.
- Misalignment of the eyes. If the disorder is acute, double vision will occur because images of objects will not coincide on the retinas.
What are the symptoms and signs of a complete lesion of the abducens nerve?
- Ipsilateral eye to deviate inward, inability to voluntarily abduct the ipsilateral eye & diplopia.
- Prevents activation of the superior oblique muscle, Ipsilateral eye is elevated, inability of ipsilateral eye to look downward when ipsilateral eye is adducted, double vision, difficulty reading, and visual problems when descending stairs.
- Ipsilateral ptosis, ipsilateral eye positioned down and out, diplopia, decreased ability to move the ipsilateral eye medially, downward, and upward, loss of ipsilateral direct pupillary light reflex, and loss of constriction of the pupil in response to focusing on a near object.
What happens to eye movements with a lesion to the medial longitudinal fasciculus?
- Cause pathologic nystagmus, which is abnormal oscillating eye movements that occur with or without external stimulation. May also produce a deficient VOR, leading to inadequate gaze stabilization.
- Produces impaired horizontal conjugate eye movements.
- Temporary ipsilateral gaze deviation, that is, the eyes look toward the damaged side.
What can happen to eye movements with lesions affecting the vestibular system or cerebellum?
- Temporary ipsilateral gaze deviation, that is, the eyes look toward the damaged side.
- Cause pathologic nystagmus, which is abnormal oscillating eye movements that occur with or without external stimulation. May also produce a deficient VOR, leading to inadequate gaze stabilization.
- Inadequate pursuit eye movements.
What can happen to eye movements with damage to the frontal eye field?
- Temporary ipsilateral gaze deviation, that is, the eyes look toward the damaged side.
- Inadequate pursuit eye movements.
What can happen to eye movements with damage to the parieto-occipital eye field?
- Temporary ipsilateral gaze deviation, that is, the eyes look toward the damaged side.
- Inadequate pursuit eye movements.
What is a tropia?
- A deviation from forward gaze apparent only when the person is looking forward with one eye and the other eye is covered.
- A deviation of one eye from forward gaze when both eyes are open.
What is a phoria?
- A deviation of one eye from forward gaze when both eyes are open.
- A deviation from forward gaze apparent only when the person is looking forward with one eye and the other eye is covered.
What is internuclear ophthalmoplegia and where is the lesion?
- Lesion is in the medial longitudinal fasciculus.
- Interruption of signals from the abducens nucleus to the oculomotor nucleus. The eye contralateral of the lesion moves normally, but the eye ipsilateral to the lesion cannot adduct past the midline when the contralateral eye moves laterally.
- Lesion is in the vestibular system.
- Interruption of signals from the oculomotor nucleus to the abducens nucleus. The eye ipsilateral of the lesion moves normally, but the eye contralateral to the lesion cannot abduct past the midline when the ipsilateral eye moves medially.
What is conductive hearing loss?
A narrowed or blocked ear canal, otitis media or inflammation in the middle ear, and a perforated tympanic membrane. Ear wax impaction, foreign bodies, and bony outgrowths can narrow or block the external auditory meatus impacting the collection and amplification of sound waves as they travel to the eardrum.
acoustic trauma, ototoxic drugs, Meniere’s disease, presbycusis, and acoustic neuroma.
What is sensorimotor hearing loss?
A narrowed or blocked ear canal, otitis media or inflammation in the middle ear, and a perforated tympanic membrane. Ear wax impaction, foreign bodies, and bony outgrowths can narrow or block the external auditory meatus impacting the collection and amplification of sound waves as they travel to the eardrum.
acoustic trauma, ototoxic drugs, Meniere’s disease, presbycusis, and acoustic neuroma.
What is an acoustic neuroma and what are some symptoms and signs?
- A benign tumor of Schwann cells surrounding cranial nerve VIII within the internal ear canal.
- If the surrounding bone did not confine the nerve, the growing neuroma could enlarge without compromising function. Unfortunately, bony restriction causes the enlarging tumor to compress the vestibulocochlear nerve, causing slow, progressive, unilateral loss of hearing. Tinnitus and problems with balance occur compressed, producing facial palsy and decreased sensation from the face. Very large tumors may interfere with the functions of cranial nerves V through X and may cause cerebellar signs by compressing the cerebellum.
- Infrequent, mild, high-pitched sounds lasting for seconds to minutes is normal, particularly in quiet environments. May be caused by medications, most often aspirin, stimulation of receptors in the ear, or central sensitization following deafferentation.
What is tinnitus?
- Infrequent, mild, high-pitched sounds lasting for seconds to minutes is normal, particularly in quiet environments. May be caused by medications, most often aspirin, stimulation of receptors in the ear, or central sensitization following deafferentation.
- Frequent, mild, low-pitched sounds lasting for hours to days is normal, particularly in loud environments. May be caused by medications, most often aspirin, stimulation of receptors in the ear, or central sensitization following afferentation.
Why do disorders within the central nervous system rarely cause deafness?
- Because auditory info projects bilaterally in the brainstem and the cerebrum.
- Because auditory info projects ipsilaterally in the temporal lobe and the cerebrum.
- Because auditory info projects bilaterally in the temporal lobe and the cerebral cortex.
What are the purposes of the oculomotor examination?
- Assesses the effect of vestibular signals on eye positioning during fast movements of the head.
- Help differentiate between peripheral vestibular disorders and CNS lesions causing dizziness or unsteadiness.
- A variety of tests assess the function of supranuclear and intranuclear pathways, brainstem nuclei, cranial nerves, neuromuscular junctions, and extraocular muscles, providing a window into nervous system functioning.
- Oculomotor examination can address the symptom of binocular diplopia or double vision with both eyes open which resolves with closure of either eye.
- To assess the ability of the eyes to rapidly switch gaze from on object to a different object.
What are the three tests used to exam the integrity of cranial nerve ll?
- Visual acuity test, visual field test & pupillary light reflex test.
- Retinoscopy test, glaucoma test & pupillary light reflex test.
- Extraocular movement test, visual field test & pupillary light reflex test.
What does visual field testing identify?
- Access the ability of both of the eyes to converge (adduct) in order to focus on objects that move towards them.
- Assess the four fields of vision, the upper, lower, nasal, and temporal quadrants in each eye, exams the entire visual pathway of each eye, from the retina through the two neurons that convey visual information to the cortex.
What is a normal response to the pupillary light reflex test?
Both eyes move inward, angling toward each other with the near point of convergence between 8-10 centimeters (3 to 4 inches)
Rapid constriction of the pupil of the ipsilateral eye and the contralateral eye.
Initial size of pupils should be the same.
Response of pupils should be equal.
both eyes moving at the same time and accurately from finger to nose in < 2 saccades.
What is an abnormal response to the pupillary light reflex test?
the inability of both eyes to move at the same time and/or inaccurately from finger to nose in >/= 2 saccades.
Absent constriction of the ipsilateral pupil.
Absent constriction of the contralateral pupil.
Absent constriction of the ipsilateral and contralateral pupil.
one eye moving toward the midline and the other eye remaining outward or both eyes remain outward, or the near point of convergence occurs at greater than 10 centimeters.
How do you know is abnormal pupillary light reflex findings are due to a cranial nerve ll, lll, or lesion in the brainstem pupil control nuclei or the connections among them?
- CN II Lesion: absent direct and consensual reflex.
- CN III Lesion: absent direct reflex, normal consensual reflex.
- Brainstem Pupil Control Nuclei Lesion or Lesions in Connections Among Them: cause additional brainstem signs.
- CN II Lesion: eyes follow the moving object, moving the eye medially, moving the eye upward when the eye is abducted, and when the eye is looking laterally, moving the eye up and down.
- CN III Lesion: eyes follow the moving object to about halfway between forward gaze and the medial corner of the eye, then down (the eye moves in, then down)
- Brainstem Pupil Control Nuclei Lesion or Lesions in Connections among Them: eyes follow the moving object to look laterally.
Why is it important to test ocular range of motion before performing the other components of the extraocular movement examination?
- Let’s the examiner know if the patient has full ocular range of motion and overall quality of conjugate eye movements in the vertical and horizontal planes.
- Let’s the examiner know if the patient has no ocular range of motion and overall quality of conjugate eye movements in the anterior and posterior planes.
What are normal findings on the smooth pursuit eye movement examination?
- Eyes move symmetrically and smoothly (same direction, same speed, same angular degree of movement)
- CN III: eyes follow the moving object, moving the eye medially, moving the eye upward when the eye is abducted, and when the eye is looking laterally, moving the eye up and down.
- CN VI: eyes follow the moving object to about halfway between forward gaze and the medial corner of the eye, then down (the eye moves in, then down)
- CN VI: eyes follow the moving object to look laterally.
- CN III: ipsilateral deficits of eye adduction, of upward movement of the adducted eye, or when the eye is abducted, deficits of up or down movements of the eye.
- CN IV: ipsilateral deficit in looking inferomedially.
- CN VI: deficit of abduction affecting only the ipsilateral eye.
What are abnormal findings on the smooth pursuit eye movement examination?
- Nonconjugate or deconjugate eye movements.
- Eye movements in particular directions is not possible or weak resulting in eyes that are not aligned at the extremes of movement.
- Conjugate or deconjugate eye movements.
- Eye movements in particular directions is possible or strong resulting in eyes that are aligned at the lows of movement.
How do you differentiate between cranial nerve lll, lV, and Vl lesions when interpreting the results of the smooth pursuit eye movement exam?
- CN III Lesion: ipsilateral deficits of eye adduction, of upward movement of the adducted eye, or when the eye is abducted, deficits of up or down movements of the eye.
- CN IV Lesion: ipsilateral deficit in looking inferomedially.
- CN VI Lesion: deficit of abduction affecting only the ipsilateral eye.
- CN IV Lesion: ipsilateral deficits of eye adduction, of upward movement of the adducted eye, or when the eye is abducted, deficits of up or down movements of the eye.
- CN III Lesion: ipsilateral deficit in looking inferomedially.
- CN VI Lesion: deficit of abduction affecting only the ipsilateral eye.
- CN III Lesion: ipsilateral deficits of eye adduction, of upward movement of the adducted eye, or when the eye is abducted, deficits of up or down movements of the eye.
- CN VI Lesion: ipsilateral deficit in looking inferomedially.
- CN IV Lesion: deficit of abduction affecting only the ipsilateral eye.
What is the purpose of testing saccadic eye movements?
- Assesses the effect of vestibular signals on eye positioning during fast movements of the head.
- Help differentiate between peripheral vestibular disorders and CNS lesions causing dizziness or unsteadiness.
- To assess the ability of the eyes to rapidly switch gaze from on object to a different object.
- Access the ability of both of the eyes to converge (adduct) in order to focus on objects that move towards them.
What are normal and abnormal findings on the saccadic eye movement exam?
- Normal: both eyes moving at the same time and accurately from finger to nose in < 2 saccades.
- Abnormal: the inability of both eyes to move at the same time and/or inaccurately from finger to nose in >/= 2 saccades.
- Normal: Both eyes move inward, angling toward each other with the near point of convergence between 8-10 centimeters (3 to 4 inches)
- Abnormal: one eye moving toward the midline and the other eye remaining outward or both eyes remain outward, or the near point of convergence occurs at greater than 10 centimeters.
- Normal: the uncovered remains directed at the target when the other eye is covered.
- Abnormal: the uncovered eye moves to look at the target.
How do you differentiate between an acute/subacute frontal eye field lesion, pontine gaze center lesion, and a medial longitudinal fasciculus lesion when interpreting the results of the saccadic eye movement exam?
- Medial Longitudinal Fasciculus Lesion: both eyes deviate ipsilaterally and are unable to direct the eyes part the midline contralaterally.
- Pontine Gaze Center Lesion: both eyes deviate contralaterally and are unable to direct the eyes past the midline ipsilaterally.
- Acute/Subacute Frontal Eye Field Lesion Lesion: one eye is unable to adduct past the midline; the other eye adducts normally.
- Pontine Gaze Center Lesion: both eyes deviate ipsilaterally and are unable to direct the eyes part the midline contralaterally.
- Acute/Subacute Frontal Eye Field Lesion: both eyes deviate contralaterally and are unable to direct the eyes past the midline ipsilaterally.
- Medial Longitudinal Fasciculus Lesion: one eye is unable to adduct past the midline; the other eye adducts normally.
- Acute/Subacute Frontal Eye Field Lesion: both eyes deviate ipsilaterally and are unable to direct the eyes part the midline contralaterally.
- Pontine Gaze Center Lesion: both eyes deviate contralaterally and are unable to direct the eyes past the midline ipsilaterally.
- Medial Longitudinal Fasciculus Lesion: one eye is unable to adduct past the midline; the other eye adducts normally.
What does the vergence exam assess?
- Assesses the effect of vestibular signals on eye positioning during fast movements of the head.
- Help differentiate between peripheral vestibular disorders and CNS lesions causing dizziness or unsteadiness.
- Presence of involuntary oscillating eye movements (nystagmus) at rest.
- Access the ability of both of the eyes to converge (adduct) in order to focus on objects that move towards them.
What are normal and abnormal findings on the vergence test?
- Normal: the uncovered remains directed at the target when the other eye is covered.
- Abnormal: the uncovered eye moves to look at the target.
- Normal: Both eyes move inward, angling toward each other with the near point of convergence between 8-10 centimeters (3 to 4 inches)
- Abnormal: one eye moving toward the midline and the other eye remaining outward or both eyes remain outward, or the near point of convergence occurs at greater than 10 centimeters.
- Normal: the uncovered eye remains steady.
- Abnormal: the eye that is quickly uncovered moves.
What do abnormal findings on the vergence test indicate?
- An abnormal response may indicate a CN IV lesion, defective visual perception, or a deficit in CNS control of visual fusion.
- An abnormal response may indicate a CN VI lesion, defective visual perception, or a deficit in CNS control of visual fusion.
- An abnormal response may indicate a CN III lesion, defective visual perception, or a deficit in CNS control of visual fusion.
What does the unilateral cover test determine?
- Unilateral cover test determines whether there is tropia.
- Whether there is phoria.
- Tests the ability to maintain gaze on an object while the head is moving which requires the VOR.
What does the cover-uncover and alternate cover tests determine?
- Unilateral cover test determines whether there is tropia.
- Whether there is phoria.
- Abnormal VOR.
What functions can eye misalignment interfere with and what are some of the symptoms?
- Weak adduction of the affected eye and abduction nystagmus of the contralateral eye.
- Restricts voluntary movement of both eyes in only one direction. If a patient with this lesion looks at a target and the examiner passively move the patient’s head, the eyes will move in the previously restricted direction.
- Interferes with depth perception and eye-hand coordination and may cause double vision, headache, eyestrain, head turn, and head tilt.
What are normal and abnormal findings on the unilateral cover test?
- Normal: the uncovered remains directed at the target when the other eye is covered.
- Abnormal: the uncovered eye moves to look at the target.
- Normal: the presence of saccades occurring when the patient looks at each of the line
- Abnormal: the inability of the patient to produce slow phase eye movements or any saccadic eye movements.
What are normal and abnormal findings on the cover-uncover test?
- Normal: the uncovered eye remains steady.
- Abnormal: the eye that is quickly uncovered moves.
- Normal: the uncovered eye does not move.
- Abnormal: the uncovered eye moves.
- Normal: the uncovered remains directed at the target when the other eye is covered.
- Abnormal: the uncovered eye moves to look at the target.
What are normal and abnormal findings on the alternate cover test?
- Normal: the uncovered remains directed at the target when the other eye is covered.
- Abnormal: the uncovered eye moves to look at the target.
- Normal: the uncovered eye does not move.
- Abnormal: the uncovered eye moves.
- Normal: the uncovered eye remains steady.
- Abnormal: the eye that is quickly uncovered moves.
What are the signs of a supranuclear lesions (a lesion superior to the nuclei for cranial nerves lll, lV, and Vl?
- Weak adduction of the affected eye and abduction nystagmus of the contralateral eye.
- Restricts voluntary movement of both eyes in only one direction. If a patient with this lesion looks at a target and the examiner passively move the patient’s head, the eyes will move in the previously restricted direction.
- Presence of involuntary oscillating eye movements (nystagmus) at rest.
What are the signs of internuclear ophthalmoplegia?
- Weak adduction of the affected eye and abduction nystagmus of the contralateral eye.
- Presence of involuntary oscillating eye movements (nystagmus) at rest.
- Problems with the pursuit phase indicate a lesion in the ipsilateral parieto-occipital pathways.
- Difficulties with the saccadic movements indicate a lesion in the contralateral frontal eye field.
What does an abnormal finding on the spontaneous nystagmus test indicate?
- Problems with the pursuit phase indicate a lesion in the ipsilateral parieto-occipital pathways.
- Difficulties with the saccadic movements indicate a lesion in the contralateral frontal eye field.
- Presence of involuntary oscillating eye movements (nystagmus) at rest.
- Peripheral vestibular loss: decreased or absent VOR (vestibulo-ocular reflex)
What is vertical nystagmus versus horizontal and rotatory nystagmus suggest?
- Rotary nystagmus is more suggestive of central pathology while horizontal and vertical nystagmus are more common in peripheral vestibular disorders.
- Vertical nystagmus is more suggestive of central pathology while horizontal and rotary nystagmus are more common in peripheral vestibular disorders.
What are normal and abnormal findings on the gaze holding nystagmus exam?
- Normal: the ability to maintain fixation (no nystagmus) in eccentric gaze
- Abnormal: nystagmus elicited in eccentric gaze
- Normal: the presence of saccades occurring when the patient looks at each of the line
- Abnormal: the inability of the patient to produce slow phase eye movements or any saccadic eye movements.
- Normal: no presence of a corrective saccade.
- Abnormal: a corrective saccade on the same side as the thrust after the head stops moving to compensate for loss of the visual target during the head movement.
What are the differences between nystagmus caused by a central nervous system lesion versus a peripheral vestibular lesion?
- Nystagmus caused by a peripheral vestibular nystagmus which does not suppress with fixation and may change direction when gaze changes direction.
- Peripheral vestibular nystagmus caused by a CNS lesion is inhibited by fixation and decreases in amplitude when gaze is indirected toward the direction of nystagmus.
- Nystagmus caused by a CNS lesion does not suppress with fixation and may change direction when gaze changes direction.
- Peripheral vestibular nystagmus is inhibited by fixation and increases in amplitude when gaze is directed toward the direction of nystagmus.
What are normal and abnormal findings on the optokinetic nystagmus exam?
- Normal: the ability to keep their eyes fixated on examiner’s nose without nystagmus.
- Abnormal: the inability to keep their eyes fixated on examiner’s nose and/or presentation of nystagmus.
- Normal: the presence of saccades occurring when the patient looks at each of the line
- Abnormal: the inability of the patient to produce slow phase eye movements or any saccadic eye movements.
- Normal: no presence of a corrective saccade.
- Abnormal: a corrective saccade on the same side as the thrust after the head stops moving to compensate for loss of the visual target during the head movement.
What do abnormal findings on the optokinetic nystagmus exam indicate?
- Problems with the pursuit phase indicate a lesion in the ipsilateral parieto-occipital pathways.
- Difficulties with the saccadic movements indicate a lesion in the contralateral frontal eye field.
- Problems with the pursuit phase indicate a lesion in the contralateral parieto-occipital pathways.
- Difficulties with the saccadic movements indicate a lesion in the ipsilateral frontal eye field.
What is the purpose of the vestibulo-ocular reflex test?
- To assess for a central vestibular disorder
- To determine if the VOR can be suppressed in order for accurate visual tracking when eye and head movements occur in the same plane or head movement is combined with visual target movement.
- Assesses the effect of vestibular signals on eye positioning during fast movements of the head.
- Help differentiate between peripheral vestibular disorders and CNS lesions causing dizziness or unsteadiness.
What are normal and abnormal findings on the vestibulo-ocular reflex test?
- Normal: the ability to keep their eyes fixated on examiner’s nose without nystagmus.
- Abnormal: the inability to keep their eyes fixated on examiner’s nose and/or presentation of nystagmus.
- Normal: no presence of a corrective saccade.
- Abnormal: a corrective saccade on the same side as the thrust after the head stops moving to compensate for loss of the visual target during the head movement.
- Normal: the ability to maintain fixation (no nystagmus) in eccentric gaze
- Abnormal: nystagmus elicited in eccentric gaze
What does an abnormal finding on the vestibulo-ocular reflex test indicate?
- Peripheral vestibular loss: increased or absent VOR (vestibulo-ocular reflex)
- CNS vestibular loss: increased or excessive VOR (vestibulo-ocular reflex)
- Peripheral vestibular loss: decreased or absent VOR (vestibulo-ocular reflex)
What is the purpose of the dynamic visual acuity test?
- Tests the ability to maintain gaze on an object while the head is moving which requires the VOR.
- To assess for a central vestibular disorder
- To determine if the VOR can be suppressed in order for accurate visual tracking when eye and head movements occur in the same plane or head movement is combined with visual target movement.
What are normal and abnormal findings on the dynamic visual acuity test?
- Normal: maintenance of visual acuity on the eye chart during head rotation.
- Abnormal: loss of visual acuity of two or more lines on the eye chart during head rotation.
- Normal: the ability to keep their eyes fixated on examiner’s nose without nystagmus.
- Abnormal: the inability to keep their eyes fixated on examiner’s nose and/or presentation of nystagmus.
What do abnormal findings on the dynamic visual acuity test indicate?
Normal VOR
Abnormal VOR
No VOR
What is the purpose of the VOR cancellation test?
- To assess the ability of the eyes to rapidly switch gaze from on object to a different object.
- Assesses the effect of vestibular signals on eye positioning during fast movements of the head.
- Help differentiate between peripheral vestibular disorders and CNS lesions causing dizziness or unsteadiness.
- To assess for a central vestibular disorder
- To determine if the VOR can be suppressed in order for accurate visual tracking when eye and head movements occur in the same plane or head movement is combined with visual target movement.
What are normal and abnormal findings on the VOR cancellation test?
- Normal: maintenance of visual acuity on the eye chart during head rotation.
- Abnormal: loss of visual acuity of two or more lines on the eye chart during head rotation.
- Normal: the ability to keep their eyes fixated on examiner’s nose without nystagmus.
- Abnormal: the inability to keep their eyes fixated on examiner’s nose and/or presentation of nystagmus.
- Normal: no presence of a corrective saccade.
- Abnormal: a corrective saccade on the same side as the thrust after the head stops moving to compensate for loss of the visual target during the head movement.
How do you interpret the findings on the VOR cancellation test?
- Restricts voluntary movement of both eyes in only one direction. If a patient with this lesion looks at a target and the examiner passively move the patient’s head, the eyes will move in the previously restricted direction.
- In most instances, a peripheral vestibular lesion will not impair smooth pursuit or VOR cancellation.
- A lesion in the central system, such as the cerebellum or vestibular nuclei, will lead to saccadic corrections.
- Problems with the pursuit phase indicate a lesion in the ipsilateral parieto-occipital pathways.
- Difficulties with the saccadic movements indicate a lesion in the contralateral frontal eye field.
Action of the Levator palpebrae superioris
eye medial
Lifts eyelid
eye up
eye down
Action of the superior rectus
eye medial
Lifts eyelid
eye up
eye down
Action of the medial rectus
eye medial
Lifts eyelid
eye up
eye down
Action of the inferior rectus
eye medial
Lifts eyelid
eye up
eye down
Action of the lateral rectus
eye medial
Lifts eyelid
eye up
eye lateral
action of the inferior oblique
If eye adducted, eye up; if eye abducted, rotates eye around the axis of the pupil.
If eye adducted, eye down and in; if eye abducted, rotates eye around the axis of the pupil
action of the superior oblique
If eye adducted, eye up; if eye abducted, rotates eye around the axis of the pupil.
If eye adducted, eye down and in; if eye abducted, rotates eye around the axis of the pupil
which optic nerve fibers does the right optic tract contain to convey visual information from the left visual field to the right primary cortex?
Right nasal and Left temporal
Left nasal & right temporal
left nasal and left temporal
right nasal and right temporal
which optic nerve fibers does the left optic tract contain to convey visual information from the right visual field to the left primary cortex?
Right nasal and Left temporal
Left nasal & right temporal
Left nasal & left temporal
Right nasal & right temporal
