Cerebellopontine Angle Masses

1. Cerebellopontine Angle Masses ALI SAFAR - PGY4 November 09, 05 University of Ottawa ENT Dept. Grand Rounds

2. Introduction • 10% of all intracranial tumors. • Fatal without treatment. • 78% are acoustic neuromas- mostly on vestibular branch. • Other CPA masses: • Meningiomas • CN schwannomas • Dermoid tumors • Arachnoid cysts • Lipomas, metastatic tumors • Vascular tumors

3. Anatomy • Potential space in the posterior fossa of the brain. • CPA boundries: • Anterior: posterior surface of temporal bone • Posterior: anterior surface of the cerebellum • Medial: lateral surface of brainstem • Lateral: petrous bone • Superior: inferior border of pons & cerebellar peduncle • Inferior: cerebellar tonsil

4. Cranial nerves: • VII & VIII • V • IX, X, XI • Important structures: • Flocculus • Lateral aperture of 4th ventrical • AICA

6. Differential • Acoustic Neuroma 60 - 92% • Meningioma • Epidermoids • Rare CPA lesions • Petrous Apex masses • Vascular malformations • Intra-axial masses

7. Acoustic Neuroma • Comprises 60-92% of CPA lesions. • Usually unilateral. • Arise from schwann cells, commonly within IAC. • Occur with equal frequency on the Superior & Inferior vestibular nerves. • Greatest density of S. cells at scarpa ganglion. • Majority of cases (95%) are sporadic. • Rarely occur on the cochlear division of the 8th CN.

8. Acoustic Neuroma • Type 2 NF: • Genetic defect on long arm of chromosome 22. • Autosomal-dominant. • Bilateral or early in life. • Assoc. with intracranial meningiomas & spinal cord tumors. • Tumors supressor gene is absent.

9. Pathology • Composed of Antoni A&B tissue. • Antoni A – compact tissue with spindle cells in palisades (most common). • Antoni B – loose tissue with cyst formation.

11. AN Manifestations • Cochlear: • Asymmetric SNHL • SSNHL • Up to 26% of AN may present with SSNHL • Only 1-2.5% of SSNHL is due to AN • Tinnitus • Decreased discrimination • Rollover phenomenon • Vestibular: • Dysequilibrium (more common) • Vertigo (less common) • Facial: • Facial weakness (suspect other tumors - epidermoid) • Hitselberger’s sign – decreased sensation of EAC due to compression of CN VII sensory roots

12. AN Manifestations • Cerebellar: • Wide gait • Falling to side of lesion • Brainstem: • Headache • Visual Loss • Other Cranial nerves: • V – facial numbness (large tumors, trigeminal schwannoma) • VI – lateral rectus palsy (rare) • IX – dysphagia (large tumors, J F S) • X – hoarseness, aspiration (large tumors, J F S) • XI – shoulder weakness (large tumors, J F S)

13. Diagnostic Tests • Audiometric Testing. • Electrophysiologic Testing. • Vestibular Testing. • CT & MRI.

14. Audiometric Testing • Pure-tone testing: • SNHL- most commonly high frequency (65%). • Normal hearing (5%). • Speech discrimination: • Scores out of proportion with pure-tone thresholds. • Some may score well. • Rollover phenomenon improve the sensitivity. • Acoustic reflex thresholds: • typically elevated or absent. • If present then reflex decay measured. • The sensitivity is 85% for detecting retrocochlear problem.

15. Electrophysiologic Testing • ABR: • Most sensitive & specific audiologic test. • Abnormalities seen: • Interaural difference in latency of wave 5 with delay of more than 0.2 msec (40-60%). • No identifiable wave forms in 20-30%. • Wave 1 present but all remaining waves are absent in 10-20%. • Normal in 10-15%.

16. Vestibular Testing • ENG: • Abnormal in 70-90%. • Unilateral weakness in caloric testing. • Spontaneous nystagmus. • Only test superior nerve. • No abnormality for smaller tumors. • Computerized dynamic posturography. • Rotary chair testing.

17. Imaging Techniques • CT • Non-contrasted • Iodine based contrast - uptake by selected lesions • CT air cisternogram – no longer performed • MRI • T1W – Fat density is bright • T2W – Water density is bright • FLAIR (Fluid Attenuated Inversion Recovery) • Gadolinium

18. Radiologic Features of AN • CT • Non-contrast: usually isodense to brain, calcification is rare • IV Contrast: Over 90% of non-treated tumors enhance homogeneously • MRI • T1W – isointense to brain, hyperintense to CSF • T2W – hyperintense to brain, iso/hypo-intense to CSF • Gadolinium – Intense enhancement of tumor on T1W

19. AN Features Centered on Porus acousticus. Acute angles to petrous bone Often involves the IAC Homogeneous enhancement No dural tail No calcifications

20. Meningioma • Second most common CPA lesion 3-7 %. • Arise from cap cells near arachnoid villi which are more prominent near cranial nerve foramina and venous sinuses. • Usually arise from posterior surface of the petrous bone and usually do not extend into IAC. • Symptoms • Ataxia. • Nystagmus. • Facial hypesthesia. • Audiologic findings may show retrocochlear pattern or may be normal.

21. Meningioma • Radiologic features • Tumors generally hemispherical with obtuse angles to petrous bone • Dural tail often present (50-75%) • May herniate into middle fossa (50%) • May show calcification (25%) • Pial blood vessels with flow voids may be present at the margins. • Treatment • Surgical removal is treatment of choice • XRT if complete excision not possible

22. Meningioma Features: • Arise from surface of petrous • bone. • Obtuse angles to petrous bone. • Uncommonly involves the IAC. • Frequently with dural tail. • Calcifications common. • Pial vessel flow voids.

24. Epidermoid • Accounts for 2-6% of CPA masses • Physiology: • Congenital lesions that present in adulthood • Rests of ectodermal tissue containing stratified squamous lining and keratin • May arise within the temporal bone or in the CPA • Benign and slow growing • Symptoms • Similar to acoustic neuroma and meningioma • Facial nerve paresis and facial twitching may occur

25. Epidermoid • Radiologic Features • May dumbell into middle fossa or contralateral cistern • Highly variable in shape with a cauliflower surface appearance • CT • mass hypodense to CSF • Do not enhance • MRI – homogeneous lesion • T1 – isointense to CSF • T2 – isointense to CSF • Differentiation from arachnoid cyst may be difficult • Diffusion weighting will show moderate intensity for epidermoids, but low intensity for arachnoid cysts.

27. Arachnoid Cyst

28. Other Extra-axial Masses • Primary • Arachnoid Cyst • Schwannomas (CN V-XII) • Hemangiomas • Lipoma • Dermoid/Teratoma • Secondary • Paraganglioma • Chondroma • Chordoma • Extension of Petrous bone tumors

29. Schwannomas • CN VII • Symptoms may be identical to acoustic schwannoma • Differentiation from acoustic schwannoma may not be possible by radiography unless lesion extends distal to geniculate ganglion. • CN IX – XI • Jugular Foramen syndrome • Dysphagia • Hoarseness • Shoulder weakness • Enlargement of Jugular Foramen • CN XII • Hemiatrophy of tongue • Enlargement of hypoglossal

30. CN V Schwanoma

31. CN VII Schwanoma

32. CN XSchwanoma

33. Vascular • Vertebrobasilar dolichoectasia • Enlongation and dilatation of the vertebrobasilar artery. • Symptomas - Facial spasm, trigeminal neuralgia • AICA loop • May loop over, under, or between CN VII & CN VIII. • Symptoms - vertigo • Giant Aneurysms • Hemangioma • Paragangliomas (may extend to CPA) • Glomus Jugulare • Glomus Tympanicum

34. Vertebrobasilar Dolichoectasia

35. AICA loop

36. Giant Aneurysms

37. Glomus Jugulare

38. Petrous Apex • Cholesterol granulomas (most common) • Epidermoid cyst • Trigeminal schwannoma • Carotid artery aneurysm • Chondroma • Chondrosarcoma

39. Cholesterol Granulomas

40. Intra-axial • Astrocytoma • Ependymoma • Medulloblastoma • Hemangioma / Hemangioblastoma • Choroid plexus papilloma • Metastasis

41. Treatment • Observation • Surgery • Translabrynthine • Retrosigmoid • Middle Fossa • Radiotherapy • Conventional radiation therapy • Stereotactic radiosurgery

42. Observation • Indications • Advanced age (over 65 or 75) • Poor health • Lack of symptoms • Non-progression of symptoms • Only hearing ear • Isolated IAC tumors in the elderly • Contraindications • Young patient • Healthy patient • Symptomatic progression • Compression of brainstem structures

43. Trans-labrynthine • Indications • Extension into CPA > 0.5 - 1cm • Non-serviceable hearing • Adequate contralateral hearing in large tumors • Contraindications • Serviceable hearing

44. Middle Fossa • Indications • Small tumor • Intracanallicular tumor • Moderate CPA involvement • Adequate hearing (SRT<50 db, Disc >50%) • Contraindications • Large tumors • Extensive CPA involvement ( > 0.5 – 1 cm) • Older patients ( > 60 yrs. may have higher rate of bleeding or stroke)

45. Retrosigmoid • Indications • Serviceable hearing • Large tumors • Compression of brainstem • Contraindications • Functional hearing with extensive IAC involvement • Intracanallicular tumors

46. Stereotactic Radiosurgery • Indications • Small tumors • Functional hearing • Older patients (>75) • Medically unstable patients • Previous resection • Contraindications • Tumors > 3 cm • Prior radiotherapy • Tumor compressing brainstem

47. Stereotactic Radiosurgery • Outcome • Local control (non-progression): 94% • Hearing preservation: 47 – 77% • Complications • Facial nerve injury: 5 - 17% • Trigeminal nereve injury: 2 - 11% • Hyrodcephalus: 3%