1/10/2013

1/10/2014

Answers:

What percentage of vestibular schwannoma patients have neurofibromatosis type 2?
A)3% 
B) 15% 
C) 50% 
D) 85% 
E) 97%

Patients w/ NF2 represent about 2-4% of VS cases.

The NF2 gene encodes what protein? What is the function of this protein?

NF2 encodes for the protein "merlin" which has functions involved with linking cytoskeletal components in the plasma membrane and in contact inhibition.

MC Questions:
Which of the following is not characteristic of the Wishart subtype of NF2?
A) Larger tumors 
B) Faster growing tumors 
C) Multiple tumors 
D) Hearing loss is related to tumor size 
E) Later age of onset of disease

Free Response Question:
Describe the difference in the presence of skin neurofibromas between NF1 and NF2.

Quick Facts:

1/9/2014

1/9/2014

Answers:

What is the most common extra-axial malignant neoplasm of the CPA?
A) Astrocytoma 
B) Chordoma 
C) Glomus Jugulare 
D) Chondrosarcoma 
E) Metastases

Mets are the most common extra-axial malignant neoplasm of the CPA.

What is "Meckel's Cave"?

Meckel's Cave, aka trigeminal cave, is an arachnoid pouch w/ CSF in it. It is formed by two layers of dura which are part of an evagination of the tentorium cerebelli near the apex of the petrous part of the temporal bone and envelops CN V. Its boundaries are: the cerebellar tentorium, the lateral wall of the cavernous sinus, the clivus and the posterior petrous face.

MC Questions:
What percentage of vestibular schwannoma patients have neurofibromatosis type 2?
A)3% 
B) 15% 
C) 50% 
D) 85% 
E) 97%

Free Response Question:
The NF2 gene encodes what protein? What is the function of this protein?

Quick Facts:
Clinical Findings
Gardner Subtype:
-early onset
-smaller tumors
-few tumors
-slower growing tumors
-hearing loss related to tumor size
Wishart Subtype:
-Later onset
-Larger tumors
-Multiple tumors
-Faster growing tumors
-Hearing loss not related to tumor size
-Usually present in 20-30s, rarely after 60.
-50% of patients present with hearing loss, it is usually progressive and associated
w/ poor speech discrimination scores.
-10% have tinnitus
-acute vertigo is uncommon due to slow growth pattern
-Skin tumors present in 2/3rds of patient as are Cafe-au-lait spots however there are
fewer than six of these (unlike in NF1)
-Juvenile posterior subcapsular lenticular opacities are common (up to 51%). Some are congenital and can be useful in diagnosis.

1/8/2013

1/8/2014

Answers:

What percentage of CPA tumors are not vestibular schwannomas?
A) 5% 
B) 20% 
C) 50% 
D) 80% 
E) 95%

20% of CPA tumors are not schwannomas. Of these ~50% are meningiomas.

What factors should prompt testing for NF2 in a patient who presents w/ a CPA tumor?

If meningiomas are present in a young patient or there are multiple meningiomas, then NF2 testing should be considered.

MC Questions:
What is the most common extra-axial malignant neoplasm of the CPA?
A) Astrocytoma 
B) Chordoma 
C) Glomus Jugulare 
D) Chondrosarcoma 
E) Metastases

Free Response Question:
What is "Meckel's Cave"?

Quick Facts:
Neurofibromatosis Type 2
-Hallmark is b/l vestibular schwannomas.
-often confused with von Recklinghausen syndrome, however this is peripheral
neurofibromatosis and is designated NF1.
-NF2 is much more rare compared to NF1 (1:50,000)
-NF2 is autosomal dominant w/ 95% gene penetrance.
-presents in 2-3rd decade.
-Pts w/ NF2 represent 2-4% of VS.
-NF2 gene encodes for protein called merlin which functions as a membrane-organizing protein.
Pathogenesis
-from inheritance of mutation in merlin protein on chromosome 22.
-Merlin involved in linking cytoskeletal components w/ plasma membrane.
-Loss of this protein could lead to loss of contact inhibition.
-50% of patients have no family hx and are likely new germ line mutations.
-NF2 mutations associated w/ protein truncation are more severe = Wishart
type
-NF2 mutations associated w/ protein missense or splicing are milder = Gardner
type

1/7/2013

1/7/2014

Answers:

Which of the following approaches to a CPA tumor is hearing ablative?
A) Retrosigmoid 
B) Middle Fossa 
C) Translabyrinthine 
D) They can all be hearing preserving as long as care is taken not to damage vital hearing structures 
E) They are all hearing ablative

The translabyrinthine approach is hearing ablative whereas the retrosigmoid and middle fossa approaches can keep hearing intact.

When is observation an adequate management strategy for vestibular schwannomas?

Observation is reasonable in older patients or in pts where the tumor does not appear to be growing significantly.

MC Questions:
What percentage of CPA tumors are not vestibular schwannomas?
A) 5% 
B) 20% 
C) 50% 
D) 80% 
E) 95%

Free Response Question:
What factors should prompt testing for NF2 in a patient who presents w/ a CPA tumor?

Quick Facts:
Treatment of CPA meningiomas
-can observe or use stereotactic radiotherapy if pt has limited life expectancy or not surgical candidate, otherwise treat w/ surgery.
-ideal surgery consists of total meningioma removal and excision of surrounding dura w/ drilling of underlying bone.
-Surgical approach depends on location of tumor and pts hearing.
-Meningiomas medial to the IAC are more common.  
-arise along inferior petrosal sinus and involve petrous apex, lateral clivus and meckel cave.
-Meningiomas lateral to IAC involve the sigmoid sinus, jugular bulb and superior petrosal sinus.  
-Approach these via retrosigmoidal approach as facial nerve is often displaced anteriorly so a retro sigmoid approach does not place the nerve between the surgeon dn the tumor. Also allows for hearing preservation.
-Limited intracanalicular meningiomas can be managed by middle cranial fossa approach to preserve hearing or translabyrinthine if pt has poor/no hearing.
-If meningioma invades cochlear or extends to clivus or meckle cave than transcochlear approach is warranted.
-60% of CPA meningiomas involve middle fossa and may need craniotomy of combine middle/posterior fossae.
Prognosis
-Total tumor removal achieved in 70-85% of cases.
-Non total removal often due to adherence to brainstem or cavernous sinus involvement.
-Long term recurrence is 10-30% if all removed, 50% if some left behind.
-Hearing preservation is ~70% (more than schwannomas)

1/6/2014

1/6/2014

Answers:

What is the average growth rate of vestibular schwannomas?
A) 0.5 mm/yr 
B) 1mm/yr
C) 1.2 mm/yr 
D) 1.5 mm/yr 
E) 1.8mm/yr

The average growth of VS is 1.8/yr. However, this can vary widely and a repeat scan should be performed 6 months after initial diagnoses to assess the growth pattern of each particular tumor.

Typically, how large must a CPA tumor be to cause cerebellar symptoms?

To cause cerebellar symptoms a VS usually has to fill the CPA which requires it to be ~ 3cm.

MC Questions:
Which of the following approaches to a CPA tumor is hearing ablative?
A) Retrosigmoid 
B) Middle Fossa 
C) Translabyrinthine 
D) They can all be hearing preserving as long as care is taken not to damage vital hearing structures 
E) They are all hearing ablative

Free Response Question:
When is observation an adequate management strategy for vestibular schwannomas?

Quick Facts:
Vestibular Schwannomas = 80% of CPA tumors.
-Of the other 20%, most are distinguished be imaging characteristics
-CPA: Bounded be temporal bone, cerebellum and brainstem
-CPA is traversed be CN V-XI.
-90% of CPA tumors are schwannomas and meningiomas, the other 10% include congenital rest lesions, intra-axial tumors, metastases and vascular lesions and lesions from skull base.
-Classic symptoms of CPA tumors include : unilateral hearing loss, vertigo, altered facial sensation, facial pain progressing to nystagmus, facial palsy, vocal cord palsy, dysphagia, diplopia, respiratory compromise and death.

1/3/2014

1/3/2014

Answers:

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

The gold standard for VS diagnosis is MRI w/ gadolinium contrast

What is the definition of "rollover"?

Rollover = Retrocochlear
pathology causes WRS to be lower than expected based on pure-tones. Often this WRS gets worse with increasing intensity of sound.

MC Questions:
What is the average growth rate of vestibular schwannomas?
A) 0.5 mm/yr 
B) 1mm/yr
C) 1.2 mm/yr 
D) 1.5 mm/yr 
E) 1.8mm/yr

Free Response Question:
Typically, how large must a CPA tumor be to cause cerebellar symptoms?

Quick Facts:
Surgical Measures for vestibular schwannomas
-Approach is based on hearing status, size of tumor and extent of IAC
involvement.
-Can be hearing preserving(retrosigmoid/middle fossa) or ablative
(translabyrinthine).
-Middle fossa = good hearing pt and tumor <1.5cm in CPA.
-Retrosigmoid = good hearing pt w/ tumor <4 cm not involving lateral IAC.

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.