1/2/2014

1/2/2014

Answers:

Rank the following complaints on presentation of vestibular schwannoma from most common to least common.
A) V2 Dysfunction > Hearing Loss > Tinnitus > Diplopia 
B) Tinnitus > Hearing Loss > Diplopia > V2 Dysfunction 
C) Hearing Loss > Tinnitus > Diplopia > V2 Dysfunction 
D) Tinnitus > Hearing Loss > V2 Dysfunction > Diplopia 
E) Hearing Loss > Tinnitus > V2 dysfunction > Diplopia

95% of VS present w/ unilateral hearing loss. 65% will present with tinnitus. Facial/Trigeminal dysfunction is another common presentation for VS. Diplopia is an unusual in early VS and is not a common presenting symptom.

The IAC is divided into 4 quadrants by what two structures?

The "transverse crest" and the "vertical crest" (aka Bill's bar)

MC Questions:
What is the best study to diagnose a vestibular schwannoma.
A) MRI w/o contrast 
B) MRI w/ contrast 
C) CT w/ contrast 
D) CT w/o contrast 
E) Angiogram

Free Response Question:
What is the definition of "rollover"?

Quick Facts:
-Natural hx of VS includes a slow growth in the IAC and then into the cisterna of the
CPA.
-Average growth rate is 1.8 mm/yr.
-Symptom onset is often slow/insidious but predictable.
-Occasional rapid progression can occur due to cystic degeneration or bleeding.
-Initial growth often affects vestibulocochlear nerve in rigid IAC causing unilateral
hearing loss, tinnitus and vertigo.
-Tumor then progresses to CPA cistern and grows freely w/o symptoms until it reaches 3 cm.
-At this point corneal/mid face numbness, further hearing loss, vertigo and facial
weakness/spasms can occur.
-Further growth causes cerebellar signs including ocular changes, headache, AMS, n/v and eventually death.

1/1/2014

1/1/2014

Answers:

What is the most common type of CPA tumor?
A) Epidermoid 
B) Glomus 
C) Meningioma 
D) Astrocytoma 
E) Schwannoma

80% of CPA tumors are vestibular schwannomas (aka acoustic neuromas)

Describe the boundaries of the CPA.

-Superior boundary = tentorium

-inferior boundary = cerebellar tonsil / medullary olives

-anterior border = posterior dural surface of petrous bone and clivus

-posterior border = ventral surface of pons/cerebellum

-medial border = cisterns of pons and medulla

-apex = region of the lateral recess of the fourth ventricle.

MC Questions:
Rank the following complaints on presentation of vestibular schwannoma from most common to least common.
A) V2 Dysfunction > Hearing Loss > Tinnitus > Diplopia 
B) Tinnitus > Hearing Loss > Diplopia > V2 Dysfunction 
C) Hearing Loss > Tinnitus > Diplopia > V2 Dysfunction 
D) Tinnitus > Hearing Loss > V2 Dysfunction > Diplopia 
E) Hearing Loss > Tinnitus > V2 dysfunction > Diplopia

Free Response Question:
The IAC is divided into 4 quadrants by what two structures?

Quick Facts:
Imaging for Vestibular Schwannomas
-gold standard is MRI w/ gadolinium contrast
-can differentiate various CPA tumors on MRI.
-VS are hypointense globular mass centered over IAC on T1 w/ enhancement w/
gadolinium. They are iso-to hypointense on T2.
Special Tests
-Average pt requires 4 years from onset of symptoms to diagnosis of VS.
-Pts w/ unilateral auditory, vestibular and facial complaints need to undergo eval to
r/o retrocochlear disease.
-Pure-tone audiograms in VSD patients show asymmetric, downsloping, high frequency SNHL in 70%.
-Retrocochlear pathology causes WRS to be lower than expected based on pure-tones. Often this WRS gets worse with increasing intensity of sound = Rollover.
-Abnormal WRs should prompt imaging.