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Disturbances of Hearing, Balance, Smell, and Taste

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An 89-year-old man has noticed that his hearing has gradually worsened with aging. The examining physician applies a vibrating tuning fork to his right mastoid process. The moment the sound can no longer be heard, the fork is held near the auditory meatus and the patient can again hear it. His deafness has probably developed because of which of the following?

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a. Calcification of ligaments stabilizing the ossicles

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b. Weakness of the tensor tympani

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c. Neuronal degeneration

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d. Weakness of the stapedius muscle

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e. Granulation tissue in the middle ear

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The answer is c. 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.

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A 65-year-old diabetic woman has aphasia secondary to a stroke involving the inferior division of the left middle cerebral artery. Her hearing is intact. Which of the following correctly reflects why dominant temporal lobe infarction will not produce complete deafness?

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a. There is no temporal lobe representation for hearing.

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b. Each cochlear nucleus projects to both temporal lobes.

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c. Deafness results with nondominant hemisphere damage.

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d. Both thalamic and temporal lobe damage must occur.

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e. Both brainstem and temporal lobe damage must occur.

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The answer is b. 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.

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A 72-year-old man is having difficulty hearing. He is being tested with a tuning fork. If he has disease of the middle ear, sound transmitted strictly by air conduction will be perceived as which of the following?

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a. Louder than that transmitted by bone conduction

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b. Quieter than that transmitted by bone conduction

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c. Lower pitched than that transmitted by bone conduction

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