Lecture 12- CNS Tumors Flashcards Preview

HESP 632 - Medical Audiology > Lecture 12- CNS Tumors > Flashcards

Flashcards in Lecture 12- CNS Tumors Deck (39)
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What are the 4 skull base neoplasms involving the posterior fossa?

1. Common cerebellopontine angle lesions
2. Petrous apex lesions
3. Uncommon cerebellopontine angle lesions
4. Inta-axial tumors


What are common cerebellopontine angle lesions (7)?

1. Acoustic neuroma/schwannoma
2. Meningioma
3. Epidermoid tumor
4. Nonacoustic neuroma/schwannoma
5. Paraganglioma
6. Arachnoid cyst
7. Hemangioma


What is a vestibular schwannoma/acoustic neuroma?

Benign schwannoma of CN8
- Most arise from vestibular division
- Derived from schwann cells
- Does not invade other neural structures


What is the site of origin of vestibular schwannoma/acoustic neuromas?

- Medial portion of the IAC
- Sometimes in the CPA, lateral to the porus acusticus


Describe the epidemiology of vestibular schwannoma/acoustic neuromas?

Diagnosis made most often between 30-60 y/o


2000-3000 diagnosed annually in USA

~95% arise de novo as a unilateral lesion

Inherited form: NF@


What are the clinical presentations of vestibular schwannomas?

Hearing related
- Unilateral or asymmetrical SNHL (95%)
- Sudden onset HL (10-20%)
- Tinnitus: high-pitched, continuous, asymmetrical

Dysequilibrium (up to 70%)

Facial hypesthesia (up to 50%)
- Most often for medium to large tumors
- Diminished corneal reflex

Headaches (40%)
- Large tumors with brainstem compression


What is the natural Hx of vestibular schwannomas?

Variable growth rates
- Average 0.2 cm/year
- 10-15% grow 1 cm/year

Three classifications

Can be fatal during a course of 5-15 years


What are the 3 classifications of vestibular schwannomas?

1) Intracanalicular (<1 cm)

2) Intracranial extention w/o brainstem distortion (1-2 cm)

3) Intracranial extension w/ brainstem distortion (>2 cm)
- BS compression
- CN5
- Hydrocephalus


How are vestibular schwannomas diagnosed?

Auditory and vestibular studies
- Impact on the functional integrity of the audiovestibular systems

Imaging studies: definitive diagnosis

Contrast enhanced MRI: gold standard
- Isointense on T1-weighted images
- Some signal increase on T2-weighted images
- Gadolinium enhancement- striking

CT with contrast
- Smoothly marginated, contrast enhancing mass for tumors over 1.5 cm


What is neurofibromatosis type 2 (NF2)?

- Multiple neoplasia syndrome
- Mutation of tumor suppressor gene - neurofibromin
- Inherited as AD trait or de novo
- Prevalence (1/60,000 people)
- Nearly 100% penetrant by age 60 years
- Phenotype: widely variable (within families less variability)


What are neurologic manifestations of NF2?

Vestibular Schwannoma
- Bilateral VS: 90-95%
- Hearing loss and tinnitus as presenting symptoms (60% adults; 30% children)
- Tumor size and rate of growth do not predict degree of HL

Meningioma: 45-58%
- 2nd most common tumor in NF2

Spinal cord ependymomas
- 18-53% of NF2 patients
- Back pain, weakness or other sensory disturbances

Peripheral neuropathy
- Most will develop


What are other manifestations of NF2 (2)?

- Lens opacities - cataracts under age 50 years specific to NF2
- Retinal hamartomas
- Epiretinal membranes

- Skin tumors in 59-68%
- Skin plaques, subcutaneous tumors and intradermal tumors
- Cafe au lait maculae


What is the diagnostic criteria for NF2?

Confirmed/definite diagnosis
- Bilateral vestibular schwannoma

Probable diagnosis
- First degree relative with NF2 and either:
Unilateral VS OR
Two of the following:
- Memingioma
- Neurofibroma
- Glioma
- Schwannoma
- Juvenile posterior subcapsular lens opacity


How are vestibular schwannomas managed?

1. Excision to prevent
- Multiple cranial neuropathies
- Brainstem compression
- Hydrocephalus
- Death

2. Surgical priorities
- Alleviate risks associated with tumor growth
- Preservation of facial nerve function
- Sparing of hearing

3. Stereotactic radiosurgery- gamma knife

4. Radiation treatment

5. Pharmacologic treatment
Lapatinib: targets signaling pathways of neurofibromin

Bevacizumab: targets tumor angiogenesis

Aspirin: targets inflammatory pathways


What are the surgical approaches for removal of vestibular schwannomas?

1) Retrosigmoid or suboccipital

2) Translabyrinthine

3) Middle fossa


What are the advantages of the retrosigmoid or suboccipital approach?

- Wide exposure
- Hearing preservation possible


What are the disadvantages of the retrosigmoid or suboccipital approach?

- Increased incidence of post-op headaches
- Higher incidence of CSF leak
- Need for more vigorous cerebellar retraction


What are the advantages of the translabyrinthine approach?

- Wide exposure not limited by tumor size
- Lower surgical morbidity
- More facial nerve reconstructive options


What are the disadvantages of the translabyrinthine approach?

Total hearing loss


What are the advantages of the middle fossa approach?

Superior hearing preservation results


What are the disadvantages of the middle fossa approach?

- Need to retract temporal lobe
- Small tumors only


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

No evidence demonstrating superiority of middle fossa vs. retrosigmoid approaches


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

No evidence demonstrating superiority of translabyrinthine vs retrosigmoid approaches


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

Patients with large tumors should be counseled about the greater than average risk for loss of servicable hearing


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

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


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

Hearing preservation surgery via the MF or the RS approach may be attempted in patients with small tumor size and good preoperative hearing


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

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


What is a meningioma?

Lobulated, tough, white-gray mass that is well circumscribed and indents adjacent nervous tissue

- 2nd most common tumor of the CNS
- Slow growing, benign
- Extratemporal most common
- Infratemporal rare
- Female to male ratio 2:1
- Most commonly diagnosed in middle and late decades
- Often an incidentaloma


What are signs and symptoms of a meningioma?

- Progressive hearing loss in 60%
- Headaches
- Imbalance
- Tinnitus
- Facial weakness or loss of taste
- Diplopia or visual disturbances
- Dysphagia


How are meningiomas diagnosed?

Audiovestibular testing
- Cannot differentiate from AN
- Fewer abnormal ABR

MRI w/ gadolinium
- T1- isointense to slightly hypointense in relation to surrounding brain tissue
- T2- less intense than AN
- FLAIR sequences
- AN tend to involve entire IAC
- More broad based and may have calcifications
- Dural tail

CT- used to define extent of bony involvement