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HESP632 Final > Temporal Bone Tumors > Flashcards

Temporal Bone Tumors Flashcards

1
Q

What are the most common skull base neoplasms involving the posterior fossa?

A
  • Common CPA tumors
  • Petrous apex lesions
  • Uncommon CPA tumors
  • Intra-axial tumors
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2
Q

What are examples of common CPA lesions?

A
  • Acoustic neuroma, schwannoma
  • Meningioma
  • Paraganglioma
  • Hemangioma
  • Epidermoid tumor
  • Nonacoustic neuroma/schwannoma
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3
Q

What is the most common tumor of the temporal bone?

A
  • VS/acoustic neuroma
  • Comprise 8-10% of all intra-cranial tumors
  • > 90% of all tumors in the CPA
  • Benign schwannoma of CN8 (most arrive from vestibular division)
  • Site of origin: medial portion of IAC, sometimes CPA
  • Diagnosis most often between 30-60 years old
  • F>M
  • ~95% de novo as unilateral lesion
  • Bilateral = NF2
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4
Q

What is the clinical presentation of VSs?

A

1) Hearing related:
- Unilateral or asymmetric: 95%
- Sudden onset HL: 10-20%
- Tinnitus: HF, constant, unilateral
2) Dysequillibrium: up to 70%
3) Facial hypesthesia: up to 50%
4) Headaches: 40% (brainstem compression)

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5
Q

What are the 3 classifications of VSs?

A

1) Intracanalicular: <1 cm
2) Intracranial extension without brainstem distortion: 1-2 cm
3) Intracranial extension with brainstem distortion: >2 cm (EX: BS compression, CN 5, hydrocephalus)

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6
Q

How do you diagnose VSs?

A
  • Auditory and vestibular studies
  • Imaging studies: definitive diagnosis
  • Contrast enhanced MRI = gold standard (isointense on T1-weighted images, some signal increase on T2-weighted images)
  • CT w/ contrast (good margins for tumors 1.5 cm+)
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7
Q

What is NF2?

A
  • Multiple neoplasia syndrome
  • Mutation of tumor suppressor gene (neurofibromin)
  • Inherited as AD trait or de novo
  • Nearly 100% penetrance by 60 y/o
  • Widely variable phenotype
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8
Q

What are the neurologic manifestations of NF2?

A
  • VS (bilateral: 90-95%; HL and T are presenting sx)
  • Meningioma: 45-58%
  • Spinal cord ependymomas: 18-53%
  • Peripheral neuropathy
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9
Q

What are cutaneous manifestations of NF2?

A
  • Skin tumors: 59-68%
  • Skin plaques, subcutaneous tumors, and intradermal tumors
  • Cafe au lait maculae
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10
Q

Describe NF2 confirmed/definite diagnosis.

A

-Bilateral VS

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11
Q

Describe probable diagnosis of NF2.

A
  • First degree relative with NF2 AND EITHER
  • Unilateral VS OR
  • Two of the following: meningioma, neurofibroma, glioma, schwannoma
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12
Q

Describe the management of VSs.

A
  • Excision to prevent: multiple cranial neuropathies, brainstem compression, hydrocephalus, death
  • Stereotactic radiosurgery (gamma knife)
  • Radiation treatment
  • Pharmacologic treatment
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13
Q

Describe the surgical priorities of for VS management.

A
  • Alleviate risks associated with tumor growth
  • Preservation of facial nerve function
  • Sparing of hearing
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14
Q

Describe possible surgical outcomes of VS removal.

A
  • Mortality: <2%
  • Complications occur in 20% of cases: CSF leak, meningitis, arterial/venous cerebral infarct, postop hemorrhage into CPA, facial nerve damage, HL
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15
Q

Describe hearing outcomes following VS removal.

A
  • Hearing preserved in 25%

- Aidable hearing in ~50%

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16
Q

What surgical approaches for VS are best for complete tumor resection and preservation of FN when serviceable hearing is present?

A

-No evidence demonstrating superiority of MF vs. RS approaches

17
Q

What surgical approaches for VS are best for complete tumor resection and preservation of FN when serviceable hearing is not present?

A

-No evidence demonstrating superiority of TL vs. RS approaches

18
Q

Does VS size matter for facial and vestibulocochlear nerve preservation with surgical resection?

A

-Patients with larger tumors should be counseled about the greater than average risk for loss of serviceable hearing

19
Q

Should small intracanalicular tumors (<1.5 cm) be surgically resected?

A

-There are insufficient data to support a firm recommendation that surgery be the primary treatment for intracanalicular VSs

20
Q

Is hearing preservation routinely possible with VS surgical resection when serviceable hearing is present?

A

-Hearing preservation surgery via MF or RS approach may be attempted in patients with small tumor size (<1.5 cm) and good preop hearing

21
Q

When should surgical resection be the initial treatment in patients with NF2?

A

-There is insufficient evidence that surgical resection should be the initial treatment in patients with NF2

22
Q

Can aspirin halt growth of sporadic VS?

A
  • Possibly

- Aspirin targets the genes/enzymes that mediate inflammation that is up-regulated in sVS

23
Q

What is a meningioma?

A
  • Lobulated, tough, white-gray mass that is well circumscribed and indents adjacent nervous tissue
  • Second most common tumor of the CNS
  • Slow growing, benign
  • Most commonly diagnosed in middle and late decades
  • Often an incidentaloma
24
Q

What are the signs and sx of meningioma?

A
  • Progressive HL: 60%
  • Headaches
  • Imbalance
  • Tinnitus
  • Facial weakness or loss of taste
  • Diplopia or visual disturbances
  • Dysphagia
25
Q

Describe the diagnosis of meningioma.

A
  • Audiovestibular testing (can’t differentiate from AN)
  • MRI with gadolinium (AN tend to involve entire IAC, dural tail)
  • CT
26
Q

Describe MRI results for meningioma.

A
  • T1: isointense to slightly hypointense in relation to surrounding brain tissue
  • T2: less intense than AN
27
Q

Describe treatment of meningioma.

A
  • Locally destructive and may invade cranial nerves
  • Treatment of choice: surgical excision
  • Hearing preservation: more likely than AN
  • Gamma knife or cyberknife
  • Recurrence in up to 30%
28
Q

What is a facial nerve schwannoma?

A
  • Uncommon temporal bone tumor
  • Very slow growing
  • Otic capsule erosion: up to 30%
29
Q

Describe the clinical presentation of FN schwannoma.

A
  • Facial nerve dysfunction (i.e. palsy, twitch)
  • Most common pattern: slowly progressive palsy, hyperfunction, recurrent episodes, progressively worse
  • Audiovestibular signs and symptoms: CHL with absent AR, SNHL from cochlear invasion, retrocochlear, vertigo from a labyrinthine fistula
30
Q

What are the clinical findings of FN schwannoma?

A
  • Facial nerve dysfunction: 25-50%
  • Mass behind TM: 29%
  • MRI: hypointense on T1, hyperintense on T2, enhanced with gadolinium
  • CT: osseous erosion
31
Q

Describe surgical treatment of FN schwannoma.

A
  • Approach varies with location
  • Occasionally possible to remove and save nerve
  • Nerve can be repaired with an interposition graft
  • Longstanding FN palsy (poorer postop FN function)
32
Q

Describe ABR recording in the OR.

A
  • Stimulus parameters: 20-30/s rate, 95 dB peSPL+
  • Earphones: Etymotic ER10A
  • Electrodes: EAC linked to Cz or Fpz (tiptrodes)
  • Filter settings: 300-1500 Hz
  • Acoustic interference during drilling
33
Q

Describe interpretation of ABRs in surgical context.

A
  • Anesthesia: little effect on ABR
  • Brain/brainstem temp: increased absolute, interpeak latencies with decreased temperature
  • Craniotomy affects on ABR: removal of CSF, exposure of nerve to air, insertion of retractors (re-establish baseline after opening and placement of retractors)
34
Q

What are direct 8th nerve action potentials (CNAP)?

A
  • Electrode on cochlear nerve near brainstem root entry
  • Stimulus and recording parameters: 64-126 trials at 20/sec, clicks of alternating or fixed polarity, lower amplification gain, same filters as ABR
35
Q

Describe the detection and interpretation of changes in CNAP.

A
  • Baseline with understanding of inherent variability imperative
  • Moving electrode can change response
36
Q

Describe relationship of FN monitoring to outcomes.

A
  • Small increases in proportion with HB Grades I or II
  • Great decrease in incidence of HB Grade V or VI
  • Current standard of care in VS surgery
37
Q

Describe relationship of cochlear nerve monitoring to outcomes.

A
  • ABR sensitive but not specific
  • Tumors <2 cm: 30-45% “useful for adequate hearing preservation”
  • Success has more to do with surgical approach and identification of small tumors
  • CNAP better predictor of outcome than ABR or ECochG

HESP632 Final (7 decks)

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