Background

Question 1

Cell of origin for Vestibular schwanommas and acoustic neruomas?

Answer 1

Schwann cell of myelin sheith

Question 2

Which CN do AN affect

Answer 2

VIII , more the vestibular part

Question 3

Which anatomic region do vestibular schwanommas arise?

Answer 3

CPA (cerebellopontine angle)

Question 4

Most common presenting symptoms?

Incidence?

Which cranial nerves?

Answer 4

1. Hearing Loss (95%)–VIII cochlear
2. Tinnitus (63%) –> VIII cochlear
3. Coclear nerve unsteadiness/veering/tilting (61%)–>VIII vestibular
4. facial paresthesia or pain (17%) (CN V)
5. facial paralysis (6%) –> CN VII

Question 5

median age?

if Symptomatic they will present at what age?

what % of population have subclinical ANs?

what % of intracranial tumors? incidence?

Answer 5

1. 50
2. 30-50
3. up to 1% on autopsy series in general population
4. 5-8% of intracranial tumors, incidence is 1/100,000 person years

Question 6

What proportion are sporadic?

What % of AN are bilateral and what genetic abnormality?

What protein is abnormal?

How do B/l ANs do compared to unilateral ANs

Answer 6

1. 90% are sporatic and unilateral
2. 10% are bilateral and associated with NF-2 tumor suppressor in chromosome 22
3. merlin or schwannomin (actin cytoskeletin organization)
4. similar failure rates to unilateral lesions

Question 7

Name of anatomic layer of CN VIII that gives rise to most ANs?

What are antoni A and B areas on histopath?

What do ANs stain on immunohistochem?

Answer 7

1. Obersteiner-redlich zone (junction between central and peripheral myelin) gives rise to most ANs
2. Zones of dense and sparse cellularity respectively
3. S-100

Question 8

What other risk factors other than NF2 for development of ANs?

Answer 8

1. Loud noise (ORR 13)
2. parathyroid adenoma 3.4
3. childhood radiation exposure RR per Gy is 1.14