ACOUSTIC NEUROMA Diagnosis and Management

ENT diagnosis and management

1. A COUSTIC NEUROMA DR. SHRIYA KESHAV

2. INTRODUCTION Benign tumour arising from proliferation of Schwann cells around the neurilemmal glial junction. Well circumscribed, encapsulated, slow growing Arise from Schwann cells of vestibular nerve Locally invasive.

3. INCIDENCE Constitute 8-10% of all intracranial tumors Constitute 80% of all CP angle tumors Affects 10/million per year No gender bias Age of presentation: 40-60 years

4. HISTORY: 1 st observed at autopsy in 1777. Sir Charles Bell : 1 st clinical case -1833 1 st successfully removed in 1894 by Sir Charles A Balance – Meningioma Annandale in Edingburgh 1 st successful VS removal. Koch & Henneberg coined the term Cerbellopontine angle tumor in 1902.

5. ETIOPATHOGENESIS Origin: IAC, enlarging the porus & extending into CPA . Transitional zone ( Obersteiner -Redlich junctional zone) : region at which schwann cells & neuroglial supporting cells meet Vestibular ganglia in IAC has highest concentration of Schwann cells

6. SITE: Inferior vestibular nerve sheath ( new) Superior Vestibular nerve sheath (previous) Rare : Cochlear portion of VIII cranial nerve or facial nerve

7. ETIOPATHOGENESIS Merlin gene mutation Sporadic , both copies Familial, one mutated merlin ETIOPATHOGENESIS

8. ETIOPATHOGENESIS NF-1 (Von Recklinghausen disease) have intra & extra cranial tumors , <5% U/L VS NF-2, most of these patients develop B/L VS- 95% NF 2 GENE is located on chromosome 22q12 - codes for schwannomin (merlin)- Deficiency leads to loss of control over schwann cell proliferation ETIOPATHOGENESIS

9. PATHOLOGY Origin: Transition zone. Small tumors are usually pink or yellow and rubbery . Large tumors are yellow, mottled appearance and cystic.

10. Cranial nerves may be stretched on the surface. Blood vessels may be adherent to the capsule (AICA) Dural invasion is rare .

11. MICROSCOPY ANTONI A More common Have elongated spindle cells with whorling or palisading nuclei aligned in rows called V erocay bodies ANTONI B Loose and less cellular Has a spongy appearance

12. GROWTH OF TUMOR Initial tumor arising from the vestibular nerve. Tumor expands to fill most of the IAC IAC is widened with some bone resorption.

13. GROWTH OF TUMOR Tumor occupying half of the pontine cistern. Extending to the cerebellum. Tumor compressing the cerebellum,brainstem and the Vth nerve

14. CLASSIFICATION- based on size

15. GROWTH RATE Varies in each tumor Mean growth rate is 1.1mm/year Slow growth-0.02 cm per year Medium growth-0.20 cm per year Fast growth-1.00 cm per year

16. PHASES OF TUMOR GROWTH INTRACANALICULAR CISTERNAL COMPRESSIVE HYDROCEPHALIC

17. MEDIAL VESTIBULAR SCHWANNOMA Defined as the tumour without lateral extension into the IAC IAC is not widened in CT scan Cerebellar, trigeminal symptoms with relatively better hearing

18. CYSTIC VESTIBULAR SCHWANNOMA Represents the degenerative change or coalescence of microcysts in the Antoni A tissue. Three criteria Hypodense / hypointense area on CT /MRI Identification of cystic elements perioperatively Histology S-100 positive

19. CLINICAL PRESENTATION SYMPTOMS : First symptom is usually slowly progressive hearing loss(sensorineural) with noise distortion (95%), normal hearing in 5% & 20% sudden HL Tinnitus Vertigo Loss of sensation of the face.

20. CLINICAL PRESENTATION SIGNS : Loss of corneal reflex Hitzelberger’s sign- numbness of the postero -sup wall of the EAC. Large tumors - compress the lower cranial nerves- cause voice change, aspiration dysphagia .

21. Cerebellar signs in case of large tumors . The motor component of the facial nerve is more resistant to compression. Usually unilateral involvement. Vestibular symptomatology is usually subtle due to the compensation by the contralateral labyrinth.

22. DIAGNOSIS Pure tone audiometry : unilateral high frequency hearing loss.

23. DIAGNOSIS Speech discrimination: reduced to less than 50%. Stapedial reflex decay test : decay to half amplitude in 5 sec or less. Tone decay test-of 30db or more Recruitment absent

24. BERA Most sensitive Prolonged wave V absolute latency. Interpeak latency – excellent sensitivity Prolonged wave I-V interwave time interval Complete absence of wave V Distorted morphology of waves.

25. BERA IN VS 10-20 % with only wave I and nothing thereafter 40-60 % with wave V latency delay >0.2ms interaural delay of wave V latency 10-15 % have normal findings

26. VESTIBULAR TESTS Not sensitive or specific means of diagnosis Reduced caloric response in affected ear Electronystagmogram (ENG) evaluates LSCC, innervated by superior vestibular nerve Extent of vestibular function predicts post op vertigo

27. IMAGING CT SCAN : VS appears as isodense or hypodense mass , relative to pons and adjacent brain . Widening of ipsilateral CPA cistern

28. MRI with gadolinium-gold standard: Detects VS of all sizes. T1- VS is hyperintense compared to CSF and isointense to gray matter. T2- VS appears isointense to the CSF and hyperintense to gray matter.

29. FACTORS THAT INFLUENCE MANAGEMENT Tumour size. Hearing preservation. Age and medical conditions of the patient. Experience of the surgeon. Patient’s preference.

30. TREATMENT OPTIONS Conservative management Surgical excision- T ranslabyrinthine approach Middle cranial fossa approach S uboccipital approach Combined approach Steriotactic radiation

31. TUMOR FEATURES MANAGEMENT Intracanalicular <5mm Observation Intracanalicular 5-10mm Middle fossa Suboccipital SRS CP angle extension 10-25mm Suboccipital + Translab . SRS CP angle extension 25-35 mm Suboccipital . Translab . CP angle extension 35-50 mm Suboccipital Debulking + SRS

32. CONSERVATIVE MANAGEMENT Advanced age (> 65 ) Short life expectancy (< 10 years) Slow growth rate Poor surgical candidate / poor general health Minimal symptoms Only hearing ear Patience preference

33. STEREOTACTIC RADIO SURGERY Leksell 1969. Modalities: Gamma knife, LINAC, Proton Beam. Tumour control is achieved in 85 % of pts. Dose schedules have been modified to reduce the risk of CN complications. Role in hearing preservation .

34. Indications: Refusing / contraindication of open surgery Recurrent or incompletely resected tumour NF and bilateral tumours. Patient preference.

35. PRINCIPLES Localization - fixed or removable headframe , or patient’s own anatomy to determine a Cartesian based co-ordinate system . W ith magnetic resonance imaging (MRI), used to target pathological lesions including skull base tumours .

36. I onizing radiation to ablate a volume of tissue, or to alter its biological activity, thus preventing further growth . D ose of radiation delivered in a single treatment (stereotactic radiosurgery (SRS )) or in several fractions (stereotactic radiotherapy (SRT).

37. SRS restricted to targets less than 3 cm in diameter and steep dose gradients are essential due to the risk of damaging adjacent normal tissue .

38. The delivery equipment for SRS can be broadly divided into two categories: M odified conventional linear accelerators D edicated stereotactic devices

39. MODIFIED CONVENTIONAL LINEAR ACCELERATORS used to treat a wide range of indications readily available modification often required to the machine to enable it for stereotactic use, such as a secondary highresolution small field multi-leaf collimator (MLC).

40. DEDICATED STEREOTACTIC MACHINES CyberKnife linear accelerator ( Accuray ) and the Gamma Knife unit ( Elekta ) high-precision patient localization and high-resolution radiation beam collimation deliver dose with sub-mm precision without need for modification.

41. 12–13 Gy to the margin of the tumour SRS is generally recommended for tumours < 3 cm in extra canalicular diameter with no significant brainstem compression Following SRS, transient enlargement of the tumour followed by stability or even regression (i.e. ‘ pseudoprogression ’)occurs.

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