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34 Cards in this Set

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What is the commonest malignant tumor found in the skull base?
1) squamous cell ca
2) adenoca
3) adenoid cystic ca
What aret the commonest symptoms of a skull base tumor?
1) anosmia
2) blindness, diplopia
3) facial numbness
4) dysphagia, hoarseness
What are criteria of inoperability?
1) distant mets
2) patient's fragility
3) patient cooperation
4) invasion of brainstem
5) involvement of both internal carotid arteries
6) involvement of both cavernous sinuses
7) invasion of a portion of the brain that, if removed, will give a poor quality of life
8) invasion of the spinal cord
What are the two main criteria requiring orbital exenteration?
1) any involvement of extraocular muscles
2) involvement of orbital fat with poorly diff malignancy or SCCA
What percentage of cpa tumors are vestibular schwannomas?
90%
What other tumors comprise cpa tumors (other than AN)?
menigioma
arachnoid cyst
cholesteatoma
facial neuroma
metastatic lesion
What is the average growth rate of a vestibular schwannoma?
1-2mm/year
What percentage of patients with VS present with sudden SNHL?
10-22%
What percentage of patients with sudden SNHL have VS?
1.5%
What percentage of VS pts have tinnitus?
70%
What percentage of VS pts have facial weakness?
subtle deficits in 10%
Desbribe the MR characteristics of the following cpa lesions: vestibular schwannoma, meningioma, cholesteatoma, arachnoid cyst, lipoma, cholesterol granuloma
see table
What are the three main approaches to the IAC and CPA?
1) translabyrinthine
2) retrosigmoid
3) middle cranial fossa
What are advantages and disadvantages of a translab approach?
Advantages
1)minimal cerebellar retraction
2)fewer postop headaches
3)visualizes facial nerve prior to tumor dissection

Diadvantages
1) up to 21% incidence of CSF leak
2) loss of residual hearing
What are advantages and disadvantages of a retrosigmoid approach?
Advantages
1) faster approach
2) 50% hearing preservation in tumors < 2cm

Disadvantages
1) 23% incidence of postop headaches
2) 7-21% incidence of CSF leak
3) requires cerebellar retraction
4) in larger tumors, dissection precedes identification of facial nerve
What are advantages and disadvantages of a middle cranial fossa approach?
Advantages
1) 50-75% hearing preservation
2) minimal risk of CSF leak

Disadvantages
1) slightly increased risk to facial nerve if tumor originates on inferior vestibular nerve
2) requires some temporal lobe retraction
What is the most common neoplasm of the middle ear?
glomus tumor
From where do glomus tumors arise?
They arise from normally occurring neuroectocrine ells found in the jugular bulb adventitia or along Jacobson's or Arnold's nerve.
What percentage of time are glomus tumors synchronous or multicentric?
3-10%
What is the chance of metastatic change of glomus tumors?
3-4%
Are glomus tumors considered radiosensitive?
No, radioresistant.
Describe the Fisch classification of glomus tumors.
Type A: confined to the middle ear space
Type B: confined to the mastoid and middle ear: no intralabyrinthine involvement
Type C: extending to the infralabyrinthine region of the temporal and petrous apex
Type D: intracranial extension of less than 2cm diameter
Describe the Glasscock/Jackson classification of glomus tumors.
Glomus tympanicum
a) limited to promontory
b) completely filling middle ear space
c) filling the middle ear, extending into the mastoid or through the tympanic membrane to fill the EAC; may also extend anterior to the IAC

Glomus jugulare
a) involving the jugular bulb, middle ear, and mastoid
b) extending under the IAC; may have intracranial extension
c) extending into the petrous apex; may hae intracranial extension
d) extending beyond the petrous apex into the clivus or infratemporal fossa; may have intracranial extension
What is required in the evaluation of the glomus tumors?
1) PE - ear exam, neuro exam
2) Labs - CBC, 24h urine for vanilylmandelic acid, metanephrine, normetanephrine
3) Audiogram
4) Imaging - CT, MRI, arteriography
What is the differential for a clival lesion?
1) chordoma
2) meningioma
3) neuroma
4) craniopharyngioma
5) chondrosarcoma
6) brain stem neoplasm
What percentage of Meniere's Dz is bilateral?
15-30%
What is the diff dx of Meniere's Dz?
1) autoimmune inner ear dz
2) tertiary syphilis
3) vestibular schwannoma
4) perilymphatic fistula
What are the success rates for endolyphatic shunt? What about risk of SNHL?
success rate 60 - 75% drops to 50% by 5 years; 1-3% SNHL
What is the success rate and risk of SNHL for intratympanic gentamicin?
success rate 90%; 20% SNHL
should be limited to unilateral disease.
What is the success rate and risk of SNHL for labyrinthectomy?
80% success rate; 100% SNHL
What is the success rate and risk of SNHL for vestibular neurectomy?
90% success rate; 10% SMNL
For BPPV, what is the sucess rate of the Epley maneuver?
74-91% success
What is the success rate and risk of SNHL for singular neurectomy?
90% success rate, 25% risk of complete or partial HL
What is the success rate and risk of SNHL for posterior occlusion of the semicircular?
90% success rate, 20% risk of HL