Auditory and Vestibular Systems

Question 0

Human speech

Answer 0

Disproportionally accentuated pitch due to the influence of SON axons on hair cells

Question 1

Pitch of sound

Answer 1

The place of maximum vibration along the basilar membrane is interpreted as the “pitch”

Question 2

Auditory CNS pathway

Answer 2

1. Spiral ganglion neurons synapse in the dorsal/ventral cochlear nuclei
   
   • (Rostral medulla)
2. Project to the inferior colliculus via the lateral lemniscus
   (-Caudal midbrain)
   a. Some will project to superior colliculus and then cervical spinal cord (why?)
3. Projects to MGN of the thalamus
4. Projects to Primary Auditory Cortex on transverse gyrus of Heschl
   * Bilateral projection of axons everywhere except from MGN

Question 3

Conductive hearing loss

Answer 3

Most commonly due to accumulation of cerumen

Question 4

Senori-neural hearing loss

Answer 4

Can be due to…
1. Unilateral lesion of peripheral auditory structures

2. Unilateral lesion of dorsal/ventral choclear nuclei (Rostral medulla)
3. Damage to hair cells
4. Presbycusis
5. Head trauma of temporal bone

Question 5

Vestibular CNS pathway

Answer 5

1. Peripheral processes from vestibular ganglion synapes @ the vestibular nuclei (Dorsolateral rostral medulla)
2. Project to many CNS structures
   - Some => medial longitudinal fasciculus w/ III, IV, VI to dictate eye movement in response to head movement

Question 6

Benign paroxysmal positional vertigo

Answer 6

Ppts. of CaCO3 get lodged into semicircular canals w/ age

• Nystagmus, vomiting, nausea, positional imbalance
• Epley maneuver may dislodge crystals

Question 7

Meniere’s Disease

Answer 7

1. Fluctuating unilateral sensi-neural hearing loss
2. Tinnitus
3. Vertigo
   - Caused by excess fluid in inner ear; treated w/ diuretics, shunts, low-salt diet

Question 8

Schwannoma

Answer 8

Growth of tumor =>

1. Ipsilateral sensori-neural hearing loss
2. Tinnitus
3. Vertigo

Question 9

Aminoglycosides

Answer 9

Toxic drugs affecting vestibular and cochlear fnxn

*Could also occur w/ anticonvulsants, alcohols, salicylates, and even aspirin

Question 10

Cerebello-pontine angle tumors

Answer 10

Presents initially w/ deafness and nystagmus

-Expansion of tumor => involvement of other CNs

(V, VII, IX)