Background Flashcards
What is the cell of origin for vestibular schwannomas and acoustic neuromas (ANs)?
The Schwann cell of the myelin sheath is the cell of origin for ANs.
Which CN do ANs affect?
ANs affect CN VIII. Most affect the vestibular portion of the nerve.
In which anatomic region do ANs arise?
Most ANs are found in the cerebellopontine angle (CPA).
What are the most common presenting Sx, incidence, and what CNs are they associated with?
Hearing loss (95% of pts) and tinnitus (63%) → CN VIII; cochlear nerve unsteadiness/veering/tilting (61%) → CN VIII; vestibular nerve, facial paresthesia, or pain (17%) → CN V; facial paresis (6%) → CN VII. (Matthies C and Samii M, Neurosurg 1997)
What is the median age at Dx?
50 yrs
Most people with symptomatic ANs will present b/t what ages?
Most symptomatic pts are 30–50 yo.
What proportion of ANs are sporadic?
The majority (90%) are sporadic as well as unilat.
What % of ANs are bilat, and with what genetic abnormality are they associated?
10% are bilat and associated with NF-2, the tumor suppressor gene on chromosome 22.
What protein is abnl in NF-2 pts?
Merlin or schwannomin (involved in actin cytoskeleton organization)
What is the name of the anatomic layer of CN VIII that gives rise to most ANs?
The Obersteiner–Redlich zone (the junction b/t the central and peripheral myelin) gives rise to most ANs.
Subclinical ANs are present in what % of the general population?
Up to 1% (autopsy series) of the general population harbor subclinical ANs.
ANs account for what % of intracranial tumors?
5%–8% of intracranial tumors are ANs. Overall incidence is ∼1/100,000 person-yrs.
Apart from NF-2, what are 2 other risk factors that predispose to the development of ANs?
Loud noise exposure (ORR 13) and parathyroid adenoma (ORR 3.4), childhood exposure to low-dose RT (RR per Gy 1.14).
What are the Antoni A and Antoni B areas on histopathology?
Antoni A and B are zones of dense and sparse cellularity, respectively.
For what do ANs stain on immunohistochemistry?
Most ANs stain for S100.
