Central Nervous System Tumors

Question 1

Skull Base Neoplasms Involving the Posterior Fossa

Answer 1

• Common cerebellopontine angle lesions
• Petrous apex lesions
• Uncommon cerebellopontine angle lesions
• Intra-‐axial tumors

Question 2

Common cerebellopontine angle lesions

Answer 2

– Acoustic neuroma/schwannoma
– Meningioma
– Epidermoid tumor
– Nonacoustic neuroma/schwannoma
– Paraganglioma
– Arachnoid cyst
– Hemangioma

Question 3

Vestibular Schwannoma /Acoustic Neuroma

Overview

Answer 3

• Most common tumor of the temporal bone
– 8-‐10% of all intracranial tumors
– >90% of all tumors in the CPA

• Terminology
– Historically referred to as neuromas, neurinomas, neurileminomas, neurofibromas
– NIH consensus conference 1982: vestibular schwannoma

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

• Superior = inferior vestibular nerves
• Site of origin – medial portion of the internal auditory canal – Sometimes in the CPA, lateral to the porus acusticus
• Diagnosis -‐ most often between 30-‐60 y/o
• F>M
• 2000-‐3000 diagnosed annually in USA
• ~95% arise de novo as a unilateral lesion
• Inherited form: NF2

Clinical Presentations
• 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

Question 4

Vestibular Schwannoma /Acoustic Neuroma

Natural History and Diagnosis

Answer 4

Natural History
• Variable growth rates
– Average 0.2 cm/year
– 10-15% grow 1 cm/year
• Three Classifications – Intracanalicular (<1cm)
– Intracranial extension without brainstem distortion
(1-‐2cm)
– Intracranial extension with brainstem distortion
(>2cm)
* BS compression
* CN5
* Hydrocephalus
• Can be fatal during a course of 5-‐15 years

Diagnosis of VSs
• Auditory and vestibular studies – 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

Question 5

Neurofibromatosis Type 2

Answer 5

• Multiple neoplasia syndrome • Mutation of tumor suppressor gene – merlin • Inherited as AD trait or de novo
• Epidemiology
– 1/25,000 live births
– 1/100,000 people (2005 statistic)
• Nearly 100% penetrant by age 60 yr
• Phenotype – widely variable
– Within families less variability

Neurologic Manifestations
• Vestibular schannoma – 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

• Ocular
– Lens opacities; cataracts under age 50y specific to NF2
– Retinal hamartomas
– Epiretinal membranes

• Cutaneous – Skin tumors in 59-‐68% – Skin plaques, subcutaneous tumors and intradermal tumors – Café au lait maculae

Question 6

Diagnostic Criteria for NF2

NIH/NIDCD Consensus Conference -‐ 1987

Answer 6

• Confirmed/definite diagnosis
- Bilateral vestibular schwannoma
• Probable diagnosis – First degree relative with NF2 AND EITHER
– Unilateral VS or – Two of the following • Meningioma • Neurofibroma • Glioma • Schwannoma • Juvenile posterior subcapsular lens opacity