404. The answer is c. (Ropper, p 281.) This is a normal Rinne test indicating that middle ear deafness is not present. Presbycusis is the most common cause of hearing loss in the elderly. High-frequency perception is impaired in this disorder because of sensorineural damage. The neurons most likely affected in this degenerative disorder are the spiral ganglion neurons of the cochlea.
405. The answer is b. (Ropper, pp 279-288.) Hearing in each ear is represented bilaterally even at the level of the brainstem. Lesions rarely produce sufficient damage in the brainstem to cause unilateral deafness, unless they are so massive that the patient is unlikely to be responsive to most stimuli and unlikely to survive. If there is unilateral deafness, the patient should be evaluated to determine whether the hearing loss is conductive or sensorineural.
406. The answer is b. (Ropper, p 281.) The traditional test for detecting conductive deafness is the Rinne test. The vibrating tuning fork is applied to the mastoid process. When the patient can no longer hear the vibration of the fork, it is taken off the skull and moved to the external auditory meatus. With nerve deafness, acuity may be generally reduced, but perception with air conduction will be superior to that with bone conduction. This will also be true in normal persons. With conductive hearing loss, the sound waves are transmitted more effectively to the cochlea directly through the bones of the skull than through the air and along the pathway that starts at the external auditory meatus.
407. The answer is c. (Ropper, p 683.) Mastoiditis may extend either supratentorially into the temporal lobe or infratentorially into the cerebellum. Cerebellar involvement is likely to produce ataxia, vertigo, nausea, vomiting, and morning headache. Temporal lobe extension causes a fluent aphasia by damaging the Wernicke area in the superior temporal gyrus. The lesion in either the cerebellum or the temporal lobe is usually an abscess formed by bacteria responsible for the mastoiditis. Surgical removal of the abscess is essential in either location, as progression of the abscess in either the cerebellum or the temporal lobe will be lethal.
408. The answer is a. (Ropper, pp 279-288.) The principal site of damage with acoustic trauma is the cochlea. Mechanical trauma may produce a high-tone conductive loss by perforating the eardrum. A strictly acoustic insult would not be expected to convey enough energy to the tympanum to disrupt it, but it may convey enough energy to the cochlea to shear off receptor filaments from hair cells.
409. The answer is b. (Ropper, pp 288-299.) The PICA has both medial and lateral branches. The medial branches supply the brainstem. With occlusion of these, vestibular nuclei in the brainstem are infarcted, and vertigo is common. Even with an occlusion limited to the lateral branches, vertigo is likely. If no brainstem damage occurs, cerebellar flocculonodular lobule injury may induce vertigo.
410. The answer is c. (Ropper, pp 288-299.) The vertebral arteries ascend through foramens in the transverse processes of the cervical vertebrae. With bony spurs on the vertebrae or with severe atherosclerotic disease in the vertebral arteries, flow through the vertebrobasilar system may be transiently reduced when the head is extended or rotated. Because vertigo may be positional without any associated vascular insufficiency, a diagnosis of vertebrobasilar ischemia should be reached only after other causes, such as cerebellar tumor, have been eliminated.
411. The answer is d. (Fauci, pp 202-203.) Unlike the deficit of presbycusis, lower tones are most susceptible to impaired perception during the initial phases of Ménière disease. The severity of the hearing loss typically fluctuates considerably. As fluctuations in the low-tone loss abate, high tones become progressively more involved. The attacks of vertigo associated with Ménière disease usually abate as hearing loss in the affected ear peaks.
412. The answer is d. (Aminoff, pp 476-478.) Salicylates, as well as alcohol, quinine, and aminoglycoside antibiotics, may produce a toxic labyrinthitis with vertigo as a prominent feature. Vertigo is also a common sequela of head trauma or whiplash injury. Promethazine, dimenhydrinate, and meclizine are all commonly used agents to reduce symptoms of vertigo.
413. The answer is b. (Aminoff, pp 476-478.) Aspirin may produce tinnitus in persons usually unaffected by this problem. Patients on high doses of aspirin for rheumatoid arthritis are especially susceptible to this drug-induced tinnitus. Those patients with chronic tinnitus from acoustic trauma or Ménière disease will find that their symptoms worsen with aspirin.
414. The answer is c. (Ropper, pp 980-984.) Café au lait spots characteristically occur in both type 1 and type 2 neurofibromatosis. Meningiomas, acoustic schwannomas, and other types of central nervous system (CNS) tumors occur with these hereditary disorders, but the neurofibroma is the most common lesion. Type 1 neurofibromatosis develops with a defect on chromosome 17; type 2 develops with a defect on chromosome 22.
415. The answer is b. (Ropper, pp 980-984.) Schwannomas most often occur on the eighth cranial nerve (CN), but they may also develop on the fifth, seventh, ninth, or tenth CNs. With type 2 neurofibromatosis, bilateral tumors are more the rule than the exception. The tumors that develop on the eighth CN usually develop on the vestibular division of the nerve.
416. The answer is b. (Ropper, pp 216-217.) The olfactory tract divides into medial and lateral striae. The medial stria sends fibers across the anterior commissure to the opposite hemisphere. The lateral stria terminates in the medial and cortical nuclei of the amygdaloid complex, as well as the prepiriform area. This primary olfactory cortex is in area 34 of Brodmann and is restricted to a small area on the end of the hippocampal gyrus and the uncus. This distribution of fibers makes olfaction unique among the senses in that it does not send fibers through the thalamus.
417. The answer is d. (Swaiman, pp 464, 2116.) Development of genitalia and secondary sexual characteristics during puberty and adolescence is usually negligible in boys affected by Kallmann syndrome. The olfactory defect is congenital, but may be unsuspected until the hypogonadism becomes apparent. The defects responsible for both the anosmia and hypogonadism are developmental rather than acquired. Until the defect in secondary sexual characteristics becomes apparent, the affected person is usually perceived as normal.
418. The answer is d. (Ropper, p 219.) Anosmia is most likely to develop with head trauma if the trauma is sufficient to cause a skull fracture. If anosmia does occur in the setting of a skull fracture, it is likely to be permanent. With head trauma that does not cause a fracture, anosmia will persist in about 75% of cases.
419. The answer is c. (Ropper, p 220.) Ipsilateral optic atrophy and contralateral papilledema in association with an intracranial tumor constitute the Foster-Kennedy syndrome. A meningioma of the olfactory groove may produce this syndrome if it extends posteriorly to involve the ipsilateral optic nerve. Compression on the optic nerve by the tumor produces atrophy and interferes with transmission of the increased intracranial pressure (ICP) down the optic sheath. The increased ICP is reflected in the papilledema apparent in the contralateral eye.
420. The answer is d. (Ropper, pp 288-299.) Benign positional vertigo commonly affects people in middle age or older. It is characterized by recurrent attacks of rotational vertigo occurring on changes in head position, typically lying down or turning onto the side of the affected ear. The symptoms may persist on standing as well, leaving the patient with a continuous sense of disequilibrium. Provocative maneuvers (Nylan-Barany or Hallpike maneuver) are used to confirm that the patient’s complaint is due to a peripheral cause of vestibulopathy rather than a central process affecting the brainstem. In a peripheral vestibulopathy, putting the patient’s head in a position hanging at 45° off the end of the examining table, with the head turned to the affected side, will produce rotatory nystagmus with a latency of up to 40 second, a brief duration (generally less than 1 minute), and fatigability (a decrease in symptoms and signs with successive maneuvers). The cause of BPV is thought to be related to a calcified piece of otolithic material moving within the posterior semicircular canal. Treatment may include vestibular exercises, in which the patient performs provocative maneuvers at home, or maneuvers designed to free the otolith from the posterior semicircular canal.
421. The answer is a. (Ropper, pp 288-299.) Ménière disease is characterized by repeated brief episodes of fullness in the ear, tinnitus, hearing loss, and severe vertigo. The episodes may last from hours to days. Attacks may be so severe that they cause the patient to fall to the ground due to severe disequilibrium. The cause is generally idiopathic, but is thought to relate to distension of the semicircular canal and an increase in the volume of the endolymphatic fluid. For this reason, the condition has been called endolymphatic hydrops. Treatment is generally with salt restriction and diuretics. Surgery with endolymphatic shunts is of unproven value.
422. The answer is e. (Aminoff, p 704.) Aminoglycoside antibiotics may cause vestibulopathy and ototoxicity. The vestibular end organ is affected by streptomycin and gentamicin; kanamycin, tobramycin, and neomycin tend to have a greater effect on the cochlea. Disequilibrium may progress after exposure. The cause is probably related to the fact that these drugs are concentrated in the endolymphatic fluid, exposing the cochlear hair cells to high levels of the drug. Renal disease may exacerbate the effects of the drugs.
423. The answer is i. (Ropper, pp 288-299.) This patient has a history of progressive vertigo, ataxia, sensory loss, dysphagia, and hiccups, all symptoms of the lateral medullary syndrome, usually due to distal vertebral artery occlusion. This patient’s hemianopsia reflects the probable occurrence of occipital lobe infarction, perhaps related to embolism from the occluded vertebral artery. This could have occurred at the time of the lateral medullary stroke or at an independent time. The preceding history of dizzy episodes is indicative of the importance of a thorough evaluation for the cause of dizziness in the elderly patient, particularly when other symptoms occur as well.