Chpt 7: Skull Base Surgery

Front 1

What is the commonest malignant tumor found in the skull base?

Back 1

1) squamous cell ca
2) adenoca
3) adenoid cystic ca

Front 2

What aret the commonest symptoms of a skull base tumor?

Back 2

1) anosmia
2) blindness, diplopia
3) facial numbness
4) dysphagia, hoarseness

Front 3

What are criteria of inoperability?

Back 3

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

Front 4

What are the two main criteria requiring orbital exenteration?

Back 4

1) any involvement of extraocular muscles
2) involvement of orbital fat with poorly diff malignancy or SCCA

Front 5

What percentage of cpa tumors are vestibular schwannomas?

Back 5

90%

Front 6

What other tumors comprise cpa tumors (other than AN)?

Back 6

menigioma
arachnoid cyst
cholesteatoma
facial neuroma
metastatic lesion

Front 7

What is the average growth rate of a vestibular schwannoma?

Back 7

1-2mm/year

Front 8

What percentage of patients with VS present with sudden SNHL?

Back 8

10-22%

Front 9

What percentage of patients with sudden SNHL have VS?

Back 9

1.5%

Front 10

What percentage of VS pts have tinnitus?

Back 10

70%

Front 11

What percentage of VS pts have facial weakness?

Back 11

subtle deficits in 10%

Front 12

Desbribe the MR characteristics of the following cpa lesions: vestibular schwannoma, meningioma, cholesteatoma, arachnoid cyst, lipoma, cholesterol granuloma

Back 12

see table

Front 13

What are the three main approaches to the IAC and CPA?

Back 13

1) translabyrinthine
2) retrosigmoid
3) middle cranial fossa

Front 14

What are advantages and disadvantages of a translab approach?

Back 14

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

Front 15

What are advantages and disadvantages of a retrosigmoid approach?

Back 15

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

Front 16

What are advantages and disadvantages of a middle cranial fossa approach?

Back 16

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

Front 17

What is the most common neoplasm of the middle ear?

Back 17

glomus tumor

Front 18

From where do glomus tumors arise?

Back 18

They arise from normally occurring neuroectocrine ells found in the jugular bulb adventitia or along Jacobson's or Arnold's nerve.

Front 19

What percentage of time are glomus tumors synchronous or multicentric?

Back 19

3-10%

Front 20

What is the chance of metastatic change of glomus tumors?

Back 20

3-4%

Front 21

Are glomus tumors considered radiosensitive?

Back 21

No, radioresistant.

Front 22

Describe the Fisch classification of glomus tumors.

Back 22

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

Front 23

Describe the Glasscock/Jackson classification of glomus tumors.

Back 23

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

Front 24

What is required in the evaluation of the glomus tumors?

Back 24

1) PE - ear exam, neuro exam
2) Labs - CBC, 24h urine for vanilylmandelic acid, metanephrine, normetanephrine
3) Audiogram
4) Imaging - CT, MRI, arteriography

Front 25

What is the differential for a clival lesion?

Back 25

1) chordoma
2) meningioma
3) neuroma
4) craniopharyngioma
5) chondrosarcoma
6) brain stem neoplasm

Front 26

What percentage of Meniere's Dz is bilateral?

Back 26

15-30%

Front 27

What is the diff dx of Meniere's Dz?

Back 27

1) autoimmune inner ear dz
2) tertiary syphilis
3) vestibular schwannoma
4) perilymphatic fistula

Front 28

What are the success rates for endolyphatic shunt? What about risk of SNHL?

Back 28

success rate 60 - 75% drops to 50% by 5 years; 1-3% SNHL

Front 29

What is the success rate and risk of SNHL for intratympanic gentamicin?

Back 29

success rate 90%; 20% SNHL
should be limited to unilateral disease.

Front 30

What is the success rate and risk of SNHL for labyrinthectomy?

Back 30

80% success rate; 100% SNHL

Front 31

What is the success rate and risk of SNHL for vestibular neurectomy?

Back 31

90% success rate; 10% SMNL

Front 32

For BPPV, what is the sucess rate of the Epley maneuver?

Back 32

74-91% success

Front 33

What is the success rate and risk of SNHL for singular neurectomy?

Back 33

90% success rate, 25% risk of complete or partial HL

Front 34

What is the success rate and risk of SNHL for posterior occlusion of the semicircular?

Back 34

90% success rate, 20% risk of HL