CHAPTER 11

Question 1

1. A 70-year-old woman has the following Weber and Rinne test results:
   Test Left Ear Right Ear
   Weber No lateralization Lateralization
   Rinne AC > BC BC> AC

AC = air conduction; BC = bone conduction.
The patient’s otologic findings are most consistent with which of the following conditions?

(A) Otosclerosis involving the right ear
(B) Otosclerosis involving the left ear
(C) Presbycusis involving the right ear
(D) Presbycusis involving the left ear
(E) A normal examination

Answer 1

1-A. The woman has otosclerosis involving the right ear. A patient with unilateral conduction deafness hears the vibration more loudly in the affecte d ear, and bone conduction is greater than air conduction. Otosclerosis is a conduction defect and involves the ossicles of the middle ear. The most common type of hearing loss in adults, it has a strong autosomal dominant inheritance pattern. Presbycusis, the most common cause of sensorineural hearing loss in adults, affects the
cochlea or the cochlear nerve (CN VIII).

Question 2

2. All of the following statements concerning
   conduction deafness are correct EXCEPT
   (A) the sound of a vibrating tuning fork
   placed on the vertex is heard best in the
   deaf ear
   (B) it may be the result of an acoustic neu-
   roma
   (C) it may be the result of otosclerosis
   (D) it may be the result of otitis media
   (E) it may be the result of wax in the external
   auditory meatus

Answer 2

2-B. Conduction deafness is produced by interruption of the passage of sound waves through
the external or middle ear. An acoustic neuroma is a tumor of the vestibulocochlear nerve located
in the internal auditory meatus or in the cerebellopontine angle of the posterior cerebral fossa.
This tumor causes unilateral nerve deafness. In conduction deafness, a vibrating tuning fork
placed on the vertex of the skull would be heard best in the deaf ear; this is the Weber test.

Question 3

3. All of the following statements concerning
   nerve deafness are correct EXCEPT
   (A) in patients with partial nerve deafness,
   air conduction is better than bone conduction
   (B) it may result from a middle ear infection
   (C) it may result from a tumor in the internal
   auditory meatus
   (D) it may result from toxins and drugs
   (E) it may result from degenerative disease of
   the organ of Corti

Answer 3

3-B. Sensorineural, or nerve, deafness results from damage to the organ of Corti, the cochlear
nerve, or the central neural pathway Middle ear infection (otitis media) results in conduction
deafness. In patients with partial nerve deafness, air conduction is better than bone conduction.

Question 4

4. The auditory pathway includes all of the fol-
   lowing structures EXCEPT the
   (A) trapezoid body
   (B) nucleus of the inferior colliculus
   (C) inferior olivary nucleus
   (D) lateral lemniscus
   (E) medial geniculate body

Answer 4

4-C. The inferior olivary nucleus is a cerebellar relay nucleus found in the medulla. The supe-
rior olivary nucleus is an important way station in the auditory pathway; it is found in the pons
at the level of the facial nucleus.

Question 5

5. All of the following statements concerning
   the auditory system are correct EXCEPT
   (A) the membranous labyrinth is irrigated by
   a branch of the anterior inferior cerebellar
   artery
   (B) it is characterized by multiple decussa-
   tions at all levels
   (C) it is characterized by pitch localization at
   all levels
   (D) it detects sound frequencies from 20 Hz to
   50 kHz
   (E) it can discriminate intensity changes be-
   tween 1 dB and 2 dB

Answer 5

5-D. The auditory system detects sound frequencies from 20 Hz to 20,000 Hz. The membranous
labyrinth is perfused by the labyrinthine artery; this is usually a branch of the anterior inferior
cerebellar artery (in 85% of patients) but, in some cases, it is a direct branch of the basilar artery
(in 15%).

Question 6

6. All of the following statements concerning
   the tympanic cavity are correct EXCEPT
   (A) it contains the chorda tympani
   (B) it contains parasympathetic input to the
   submandibular and sublingual glands
   (C) it contains two striated muscles
   (D) it communicates with the nasopharynx
   (E) it receives sensory innervation by the va-
   gal nerve

Answer 6

6-E. The tympanic cavity contains the chorda tympani (of CN VII), which supplies taste to the
anterior two-thirds of the tongue. The chorda tympani also contains parasympathetic input to
the submandibular and sublingual glands. It contains two striated muscles, the tensor tympani
(innervated by CN V) and the stapedius (innervated by CN VII). It communicates, via the audi-
tory tube, with the nasopharynx. The tympanic branch of the glossopharyngeal nerve (CN IX)
innervates the mucosa of the middle ear.

Question 7

7. All of the following statements concerning
   the organ of Corti are correct EXCEPT
   (A) it receives input from the brainstem
   (B) it is innervated by bipolar neurons of the spiral ganglion
   (C) it contains mechanoreceptors
   (D) it contains inner and outer hair cells
   (E) it is a structure of the middle ear

Answer 7

7-E. The organ of Corti, an inner ear structure, lies within the cochlear duct. It contains the pe-
ripheral receptor cells of the auditory system, the inner and outer hair cells. Hair cells are
mechanoreceptors, receive input from the brainstem via the efferent cochlear bundle, and are in-
nervated by bipolar neurons of the spiral ganglion (of CN VIII).

Question 8

8. All of the following statements concerning
   the basilar membrane are correct EXCEPT
   (A) it separates the cochlear duct from the
   scala tympani
   (B) it has a pitch localization along its length
   (C) it is in contact with endolymph
   (D) it gives rise to the tectorial membrane
   (E) its destruction at the apex of the cochlea
   results in a hearing loss in the low-fre-
   quency range

Answer 8

8-D. The basilar membrane supports the organ of Corti, separates the cochlear duct from the
scala tympani, and is in contact with both endolymph and perilymph. The basilar membrane has a pitch localization along its length; high frequencies are registered at the base of the cochlea, low frequencies at the apex. The tectorial membrane is a projection of the spiral limbus that overlies the hair cells of the organ of Corti.

Question 9

9. All of the following statements concerning
   the hair cells of the organ of Corti are correct
   EXCEPT
   (A) they are mechanoreceptors
   (B) they project centrally to the cochlear nuclei
   (C) they are stimulated by vibrations of the basilar membrane
   (D) they are derived from the otic placode of the rhombencephalon
   (E) they contain stereocilia that are embed-
   ded in the tectorial membrane

Answer 9

9-B. The hair cells of the spiral ganglion of Corti are mechanoreceptors. Vibrations of the basi-
lar membrane force the stereocilia (microvilli) of the hair cells against the overlying tectorial membrane; this shearing force is the adequate stimulus. Hair cells stimulate the afferent bipolar neurons of the spiral ganglion, which project centrally to the cochlear nuclei of the brainstem. The inner ear is derived from the otic placode of the rhombencephalon.

Question 10

10. All of the following agents can cause nerve
    deafness EXCEPT
    (A) cytomegalovirus
    (B) marijuana
    (C) rubella
    (D) streptomycin
    (E) syphilis

Answer 10

10-B. There is no evidence to date that marijuana is a human teratogen.