VESTIBULAR SCHWANNOMA_ cp angle tumor unilateral hearing loss

vestibular schwannoma, also known as an acoustic neuroma, is a benign (non-cancerous) tumor that develops on the balance and hearing nerves in the inner ear. It most commonly causes symptoms like one-sided hearing loss, tinnitus (ringing in the ear), and dizziness or balance problems. The condition is caused by a malfunction in the Schwann cells that form the protective sheath around the vestibulocochlear nerve

1. VESTIBULAR SCHWANNOMA

2. BENIGN TUMOUR CP ANGLE SLOW GROWING NON ENCAPSULATED WELL CIRCUMSCRIBED SCHWANN CELL VESTIBULAR NERVE

3. history Sir Charles Bell-1833:first case report Sir Charles A Ballance -1894:first successful surgery Cushing first described clinical features of CP angle tumors

4. Cp angle tumors Vestibular Schwannoma Meningioma Primary cholesteatoma Arachnoid cysts Cranial Nerve schwannoma -cochlear N,VII Dermoid tumors Lipomas Vascular loop compressions

5. Anatomy of CPA Irregular potential space between cerebellum &pons Anterior-petrous temporal bone Posterior- cerebellum Medial-cisterns of pons,medulla,olive Superior-inferior border of pons and cerebellar peduncles Inferior –arachnoid of lower cranial nerves

6. Contents of cpa Cranial nerves V IX,X,XI VII,VIII AICA-labyrinthine artery Arachnoid tissue CSF

7. PATHOLOGY Arises from Obersteiner-Redlich junctional zone Meeting point of schwann cells with the neuroglial supporting cells More frequently arise from fundus of IAC Enlarge porous Grow towards CPA Inferior vestibular nerve

8. GROSS APPEARANCE Yellow or pinkish grey Rubbery consistency Depends on size & degree of degeneration Mottled,cystic Cystic variant

9. MICROSCOPY Well circumscribed, un encapsulated Nerve of origin compressed at periphery Elongated spindle cells Prominent vascularity with thick vessel walls 2 histological patterns:- Antoni A Compact,cellular Verocay bodies-whorled Antoni B Loose,less cellular,vacuolated cells spongy appearance

10. etiology Unknown Types sporadic(95%) non sporadic-NF-2,bilateral Age-40-60yrs More in females

11. Molecular biology Mutation in gene for tumor supressor protein merlin/ schwannomin -22q12 Sporadic-mutation of both copies Familial -mutation in NF-2 needs only one somatic mutation

12. erbB2,erbB3 FGF,TGFB1,PDGF,VEGF

13. Growth of tumor Develops in nerve sheath Compresses nerve Fills IAC Protrudes out of porous Resorption of bone surrounding IAC-pressure effect

14. Extrameatal growth Expands in to large,empty pontine cistern Displacement and stretching of VII,VIII on the anterior aspect AICA on the inferior aspect Compress cerebellum and V cranial nerve Displaces brainstem & IV ventricle- hydrocephalus Extend to tentorium to obstruct cochlear aqueduct Lower cranial nerves

15. classification Jackler system Based on largest extrameatal diameter Preoperative imaging 5 grades

16. EXTRAMEATAL SIZE mm GRADE I SMALL 1-10 GRADE II MEDIUM 11-20 GRADE III MODERATELY LARGE 21-30 GRADE IV LARGE 31-40 GRADE V GIANT >40

17. Growth pattern Mean growth rate-1.1mm/ yr 5 patterns: 1.Continuous 2.No measurable growth 3.No measurable growth followed by continuous growth 4.Negative growth 5.Various positive growth patterns

18. variants Medial Without lateral extention to IAM Fully extrameatal Large Cerebellar and V nerve symptom Better hearing Cystic Hypodense area on imaging Cystic elements during surgery HPE with s-100 positivity

19. SYMPTOMS Cochlear Vestibular Cerebellar V th nerve Brainstem IV ventricle VI VII,lower cranial nerves

20. Intracanalicular Unilateral progressive HL Tinnitus Vertigo-mild imbalance

21. Cisternal Worsened hearing and dysequiliibrium

22. Compressive Occasional occipital head ache Midface,corneal hypesthesia Facial weakness 2,4,6- decreased visual acuity,diplopia

23. Hydrocephalic Headache,visual changes Altered mentation Nausea,vomiting papilloedema

24. 9,10 Dysphagia,aspiration, hoarseness Poor gag reflex Vocal Cord palsy

25. Cerebellar Late Inco-ordination Wide based gate

26. Brainstem Ataxia Weakness Numbness of limbs Exaggerated reflexes

27. examination Neuro otologic examination Audiovestibular Cerebellar- nystagmus,past pointing,ataxia Cranial nerves VIII-SNHL V-absent corneal reflex,decreased facial sensation Hitzelberger’s sign VI,II-papilledema IX,X,XI-poor gag,VC palsy,shoulder palsy

28. investigations Audiometry Vestibular tests Imaging

29. audiometry PTA-mc is high frequency SNHL SPEECH DISCRIMINATION SCORE Acoustic reflex threshold Acoustic reflex decay ABR

30. Asymmetric Downsloping High frequency Sensory neural

31. Poor SDS Retrocochlear Absent acoustic reflex Acoustic reflex delay

32. ABR Absent wave V Prolonged inter peak latency Inter aural delay in wave V >0.2 ms is abnormal >90% sensitive and specific 20-30% no identifiable wave forms 10-20% only wave I present Useful in those whom MRI is contraindicated

33. Vestibular tests Non sensitive ENG with caloric testing Shows reduced caloric response on affected side Tells nerve of origin-LSCC by superior vestibular nerve VEMP-reduced in inferior vestibular nerve lesions

34. Ct scan Cheap,easily available Bone erosion-temporal bone,IAC Best for CPA Used in claustrophobia,pacemaker Not useful in early intracanalicular tumors

35. MRI Most accurate irrespective of size Nerve of origin Assess labyrinth T2 weighted Contrast enhanced T1 using Gd -gold standard

36. management Wait and watch Surgery Stereotactic radiosurgery Gamma knife LINAC

37. conservative Small tumor Good hearing Elderly Poor health Monitored with imaging after 6 months;then annually If growth rate exceeds 2-3 mm/ yr need to intervene

38. surgery Hearing status Size of tumor Extent of IAC involvement Experience of the surgeon

39. history Harvey Cushing & Walter E Dandy-1900:retrosigmoid approach William House-1960 : translabyrinthine approach

40. approaches Translabyrinthine Middle fossa Retrosigmoid preserve hearing

41. Critical issues Extent of exposure of CPA & IAC Identification & preservation of facial nerve Extent of brain retraction Facial nerve electrophysiology ABR used commonly in hearing preserving surgeries

42. translabyrinthine Primary approach Boundaries :- Mastoid facial nerve,cochlear aqueduct anteriorly Posterior fossa dura posteriorly Jugular foramen inferiorly

43. Post auricular incision Complete mastoidectomy Complete labyrinthectomy Skeletonisation of middle & posterior fossa dura Decompression of sigmoid sinus to jugular foramen Skeletonisation of IAC

44. Opening of IAC dura Identification of facial nerve Tumor removed from lateral to medial Along IAC Large tumors debulked internally Tumor capsule separated from adjacent structures

45. retrosigmoidal Good hearing <4 cm Not involving lateral IAC Modification of suboccipital approach used by neurosurgeons Versatile approach View of CPA from foramen magnum to tentorium Medial IAC also approachable Does not violate inner ear

46. Curvilinear incision 6 cm long in retromastoid area Soft tissue and musculature elevated 5*5 cm craniotomy with anterior limit-sigmoid sinus & superior limit – transverse sinus Dura opened along sigmoid sinus Cerebellum retracted medially

47. CPA seen IAC seen after removing a piece of posterior bone over it Endolymphatic duct and sac limit entry to inner ear Facial nerve is anterior to the tumor Tumor removed Closure

48. Persistent post operative head ache meningeal irritation , dissection of suboccipital musculature CSF leak in cellular mastoid Cerebellar retraction Inability to directly access facial nerve

49. Middle fossa approach Good hearing: PTA <30dB <1.5 cm in CPA

50. Curved incision centered over the ear Temporalis muscle reflected inferiorly Squamous temporal bone exposed 5*5 cm temporal craniotomy centered over zygomatic root Extradural elevation of temporal lobe Floor of temporal bone exposed

51. Greater superficial petrosal nerve-anterolateral Arcuate eminence-posterior IAC dura opened posteriorly to safe guard facial nerve From medial to lateral Air cells sealed closure

52. Entire IAC visible except medial most without damage to inner ear Facial nerve position Temporal lobe retraction Auditory hallucinations Speech & memory disturbances

53. translabyrinthine No cerebellar retraction Any size tumor removed Facial nerve guarded Ease of access for facial nerve graft Residual Hearing impaired CSF leak-through incision site/nose

54. Middle fossa Hearing may be preserved Good access to fundus Less access to CPA Retraction of temporal lobe Limited size Facial nerve at risk

55. retrosigmoid Hearing preserved Any size Cerebellar retraction Limited view to fundus Facial nerve graft difficult Post operative headache

56. Stereotactic radiosurgery Single fraction of ionising radiation- Leksell Gamma knife,cyber knife,Xknife Specific target tissue based on imaging Irrespective of histology Precisely Collimated beam used Gamma ray :-photons from Co-60 LINAC:- X- rays

57. They prevent further growth and not remove tumor Causes necrosis & vascular fibrosis;edema Takes 1-2 years Preserves hearing & facial nerve Follow up

58. Advantages: Less hospitalisation No surgical risks As salvage in recurrence after surgery

59. Complications:- Cranial neuraopathies Hydrocephalus Radiation induced malignancies

60. Outcomes & complications Tumor size Surgeon experience & skills

61. complications Death , stroke,hemorrhage,venous air embolism,brain injury,herniation Cranial neuropathies –VII most common CSF leak- most common Meningitis- bacterial,aseptic Pneumocephalus

62. outcomes Deafness , imbalance,facial weakness Hearing preservation- Tumor size Preoperative hearing level 20-70 % preserved Hearing rehabilitation BAHA,cochlear implant Vertigo Tinnitus Residual tumor/recurrence Quality of life