Eighth Nerve Disorders

Question 1

Acoustic Neuroma

Answer 1

most common retrocochlear lesion, benign tumor of 8th cranial nerve schwann cells, slow growing, unilateral

Question 2

Acoustic Neuroma Etiology

Answer 2

increased proliferation of schwann cells, commonly grow in internal auditory canal out into cerebellopontine angle (CPA), if grows large it can compress brainstem

Question 3

Acoustic Neuroma Incidence & Prevalenc

Answer 3

1-2/100,000 individuals, 3,000 new cases in US each year

average age of diagnosis: 50 years, slightly higher occurrence in women, Caucasians

Question 4

Acoustic Neuroma signs & Symptoms

Answer 4

tinnitus, SNHL (85-95%) of AN cases present HL, tumor pressing against vertebrobasilar blood supply, tumor size matters

sudden HL in 10% of cases, disequilibrium, abnormal gait–slow tumor growth allows central system to compensate, reduced speech rec in affected ear

Question 5

Acoustic Neuroma Medical Evaluation & Treatment

Answer 5

MRI for diagnosis, surgery gamma knife, monitor

Question 6

Auditory Neuropathy

Answer 6

any condition in which gross discrepancies between cochlear and neural function measures exists in auditory system

normal cochlear receptor hair cell activity and abnormal VIII CN function

Question 7

Auditory Neuropathy Epidemiology

Answer 7

rare disorder, accounts up for 10% of newly diagnosed childhood HL, 7% of permanent HL in kids, seen in less than 2% of high risk infants

Question 8

Auditory Neuropathy risk Factors

Answer 8

hyperbilirubinemia, anoxia/hypoxia, low birth weight, prematurity, exchange transfusion

Question 9

Auditory Neuropathy Etiology & Pathology

Answer 9

genetics, trauma, infection, metabolic issue

mutation of OTOF gene which disrupts production of otoferlin protein which is involved in synaptic vesicles of IE

Question 10

Auditory Neuropathy Site of Lesion

Answer 10

IHC, synapses between IHC and type 1 radial afferent nerve fibers or auditory nerve damage with myelin or axon

Question 11

Auditory Neuropathy Symptoms

Answer 11

spectrum, normal-profound SNHL, bilateral HL 95% of cases, tinnitus, vestibular portion possibly,

very variable from day to day, absent acoustic reflexes, may observe roll-over in WRS

Question 12

Auditory neuropathy and WRS scores

Answer 12

roll-over due to taxing the system, increasing level of stimulus beyond certain points leads to neural fatigue and less synchronous firing of auditory nerve which shows worse and worse WRS

speech in noise is bad