A 23-year-old man comes to the physician for evaluation of decreased hearing, dizziness, and ringing in his right ear for the past 6 months. Physical examination shows multiple soft, yellow plaques and papules on his arms, chest, and back. There is sensorineural hearing loss and weakness of facial muscles bilaterally. His gait is unsteady. An MRI of the brain shows a 3-cm mass near the right internal auditory meatus and a 2-cm mass at the left cerebellopontine angle. The abnormal cells in these masses are most likely derived from which of the following embryological structures?

A 56-year-old man comes to the physician because of worsening double vision and drooping of the right eyelid for 2 days. He has also had frequent headaches over the past month. Physical examination shows right eye deviation laterally and inferiorly at rest. The right pupil is dilated and does not react to light or with accommodation. The patient's diplopia improves slightly on looking to the right. Which of the following is the most likely cause of this patient’s findings?

A 25-year-old man is brought to the emergency department 30 minutes after he was involved in a motorcycle collision. He was not wearing a helmet. Physical examination shows left periorbital ecchymosis. A CT scan of the head shows a fracture of the greater wing of the left sphenoid bone with compression of the left superior orbital fissure. Physical examination of this patient is most likely to show which of the following findings?

A 2850-g (6-lb 5-oz) newborn is delivered at term to a 19-year-old primigravid woman via normal spontaneous vaginal delivery. The mother has had no prenatal care. Examination of the newborn in the delivery room shows a small, retracted jaw and hypoplasia of the zygomatic arch. This patient's condition is most likely caused by abnormal development of the structure that also gives rise to which of the following?

A 63-year-old man comes to the physician because of a 1-month history of difficulty swallowing, low-grade fever, and weight loss. He has smoked one pack of cigarettes daily for 30 years. An esophagogastroduodenoscopy shows an esophageal mass just distal to the upper esophageal sphincter. Microscopic examination confirms the diagnosis of locally invasive squamous cell carcinoma. A surgical resection is planned. Which of the following structures is at greatest risk for injury during this procedure?

A 65-year-old man comes to the physician because of double vision that began this morning. He has hypertension and type 2 diabetes mellitus. He has smoked two packs of cigarettes daily for 40 years. His current medications include lisinopril, metformin, and insulin. Physical examination shows the right eye is abducted and depressed with slight intorsion. Visual acuity is 20/20 in both eyes. Extraocular movements of the left eye are normal. Serum studies show a hemoglobin A1c of 11.5%. Which of the following additional findings is most likely in this patient?

A 54-year-old man comes to the emergency department because of a 3-week history of intermittent swelling of his left arm and feeling of fullness in his head that is exacerbated by lying down and bending over to tie his shoes. Physical examination shows left-sided facial edema and distention of superficial veins in the neck and left chest wall. Which of the following is the most likely cause of this patient's symptoms?

A 9-year-old boy is brought to the physician for evaluation of 2 months of progressive clumsiness, falls, and increased urinary frequency. Physical examination shows bilateral temporal visual field loss. An MRI of the head shows a small calcified suprasellar mass. The patient undergoes surgery with complete removal of the mass. Pathological examination of the specimen shows a lobular tumor composed of cysts filled with oily, brownish-yellow fluid. This mass is most likely derived from which of the following structures?

A 78-year-old right-handed man with hypertension and hyperlipidemia is brought to the emergency department for sudden onset of nausea and vertigo 1 hour ago. Physical examination shows 5/5 strength in all extremities. Sensation to light touch and pinprick is decreased in the right arm and leg. A CT scan of the brain shows an acute infarction in the distribution of the left posterior cerebral artery. Further evaluation of this patient is most likely to show which of the following findings?