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Vestibular schwanoma
- 2. INTRODUCTION neuromas or neurinomas most common lesion at CPA 6% to 8% benign
- 3. HISTORY neuroma : Virchow => cochlear nerve Schwann cells => vestibular division => vestibular schwannoma (1992) 1777, Sandifort => 1st medical report of VS 1830 ,Charles Bell => accurate description 19th century, Babinski and Jackson => accurate localization
- 4. Von Bergmann => 1st surgery(1890) 1894 by Balance => 1st successful surgery unilateral suboccipital craniectomy , Woosley in 1903 translabyrinthine approach Cushing’s writings surgical microscope => 1961 by William 20th century : 86% => 20% by Harvey Cushing
- 5. House => 10% Modern-era =>0.8% and 5% 1969 , Lars Leksell and Bjorn Meyerson => 1st Gamma Knife
- 6. EPIDEMIOLOGY 1.6 per 100,000 annually mean age : 58 years both sexes are affected equally high-dose ionizing radiation Sughrue and colleagues ,growth rate > 2.5 mm/yr Stangerup and Cayé-Thomasen : intrameatal tumors : 83% extrameatal extension : 17 %
- 7. rate of hearing preservation : wait-and-watch approach Cystic lesions => sudden and dramatic growth =>higher rates of facial palsy =>reduced rates of hearing preservation Solid lesion => slow & gradual => dec rate of facial palsy => inc rate of hearing preservation 25% : observation microsurgical resection : 90% to 53% radiosurgery : 5% to 24%
- 8. ASSOCIATION : NF2 1822, Wishart => bilateral VS => NF-2 sporadic cases of VS => tumor occur unilaterally NF-2 => bilateral VS Faster growth rate Early age 1 in 35,000,
- 9. autosomal dominant 22q12.2 merlin protein 2015 : 9 clinical trails bevacizumab
- 10. DIAGNOSTIC CRITERIA :NNFF Probable NF2: Unilateral VS and age less than 30 years plus one: meningioma, glioma, schwannoma, juvenile posterior subcapsular lenticular opacities, or cortical cataract Two or more meningiomas plus Unilateral VS and age less than 30 years or One of the following: meningioma, glioma, schwannoma, juvenile posterior subcapsular lenticular opacities, or cortical cataract
- 11. Definite NF2: Bilateral VS or First-degree relative with confirmed NF2 plus Unilateral VS and age less than 30 years or Any two of the following: meningioma, glioma, schwannoma, juvenile posterior subcapsular lenticular opacities, or cortical cataract
- 12. HISTOPATHOLOGY Obersteiner-Redlich zone : transition point between glial and Schwann cells 90% : inferior division of the vestibular nerve well-circumscribed, encapsulated lesions that splay
- 13. Gross Appearance : Rubbery gray and yellowish areas hemorrhage and cyst formation
- 14. • Microscopic features : Antoni A: compact spindle cells with elongated nuclei & ample pink cytoplasm Antoni B : loosely arranged cells with multipolar processes & microcyst formation Verocay bodies :alternating arrangment of palisading nuclie & cell bodies S-100 & vementin
- 16. INVESTIGATIONS Routine : Cbc Suce PT/APTT/INR Chest x-ray Hep B & C LFT ECG Echo
- 17. Specific : CT scan brain MRI brain with contrast • Relevant : CT angiogram MRV Rinne’s test Weber test Pure tone audiometry
- 18. RADIOLOGY trumpeted internal acoustic meatus [IAM] sign ice-cream cone appearance CT scan : often erosion and widening solid portion : isodense cystic portions : hypodense beam hardening artifact Calcifications are rarely seen
- 19. MRI : T1 : 2/3 : hypointense, T2 : hyperintense Contrast T1 : enhancement • CT Angiogram : >4 cm
- 25. AIMS OF TREATMENT quality of life hearing facial nerve function Serviceable hearing : 50/50
- 26. INTRAOPERATIVE MONITORING VII CN monitoring VIII CN monitoring Brain stem auditory evoked responses Direct chochlear nerve action potential monitoring
- 27. SURGICAL APPROACHES retrosigmoid (RS) MCF translabyrinthine (TL) Main factors: tumor size extent of cisternal versus intracanalicular growth baseline hearing function patient preference surgeon’s preference and comfort level
- 28. Ansari & co-workers :2012 Hearing preservation: <1.5 cm, MCF :43.6% ,RS : 64.3% , p < .001 serviceable hearing : 63% to 88% • Facial nerve dysfunction: intracanalicular tumors , RS : 4% ,MCF: 16.7% p < .001 <1.5 cm, MCF :3.3%,TL: 11.5%, RS: 7.2%, p = .001 1.5 to 3.0 cm, the RS :6.1% , MCF: 17.3%, TL :15.8% >3.0 cm , RS :30.2% , TL: 42.5%, p < .001 Complications : CSF leak : RS group:10.3% ,MCF : 0% , TL :8%,p <.001
- 30. RECTOSIGMOID APPROACH INDICATIONS : Work horse : skull base surgery anterolateral posterior cranial fossa Rapid & easy access to CPA larger tumors with brainstem compression intracanalicular tumors with good hearing “minimally invasive” endoscopic approach
- 33. TECHNIQUE supine position , head turned to the contralateral side shoulder roll is avoided not overrotate the head Pressure points : padded 1 g/kg of mannitol, cefazolin 2g, dexamethasone 10mg Intraoperative monitoring intracanalicular component : a curvilinear incision Cisternal part : small craniotomy thru linear incision dissection
- 34. curved cerebellar retractor Neuronavigation drill away the outer table exposing the dura of the posterior cranial fossa Air cells of the mastoid C-shaped dural opening operating microscope facial nerve internal debulking
- 35. Tumor resection Facial nerve Hemostasis Duroplastry : bovine pericardium patch Copious irrigation with antibiotic solution Wound closed in layers 24 hours observation in icu MRI next morning
- 37. MIDDLE CRANIAL FOSSA APROACH dominant intracanalicular component small or absent cisternal component hearing preservation temporal retraction : seizures
- 39. TECHNIQUE Mayfield head holder squamous part of the temporal bone : parallel floor of MCF : vertical Mannitol : 1g/kg , cefazolin 2g, dexamethasone 10mg Neuromonitoring lumbar puncture or lumbar drain horseshoe incision squamous part of the temporal bone
- 40. 4-cm × 4-cm craniotomy 1/3 : anterior to EAM , 2/3 : posterior to EAM operating microscope Bleeding Direct stimulation IAC location Drilling
- 41. entire labyrinthine segment of the facial nerve tumor is mobilized cochlear nerve vestibular nerve labyrinthine artery Hemostasis abdominal fat exposed air cells
- 42. Dural closure temporalis muscle : 0.5% bupivacaine Wound 24 hours observation MRI next morning
- 43. TRANSLABYRINTHINE APPROACH good outcomes in experienced hands Hearing large tumors no serviceable hearing facial nerve transosseous nature lack of cerebellar retraction limited access : CPA ,foramen magnum ,jugular foramen
- 44. TECHNIQUE Supine , head turned to oposite shoulder roll : ipsilateral shoulder squamous part of the temporal bone : parallel C-shaped incision dissection myocutaneous flap labyrinthectomy IAC is exposed
- 45. dura is opened intracapsular debulking tumor resection risk to the pons and the facial nerve hemostasis Wound 24 hour MRI
- 48. STEREOTACTIC RADIOSURGERY 1971 by Leksell an incision Hospitalization little immediate morbidity facial palsy, hearing loss, vestibular dysfunction facial spasm, facial numbness, cerebral/brainstem edema, and hydrocephalus excellent local tumor control
- 50. COMPLICATIONS Intraoperative : Facial nerve injury : proximal to geniculate ganglion Chochlear nerve injury: vasoactive agent => nimodipine Vascular injury Postoperative : HCP : 18% Headache : 1/3 CSF leak : 8-30% Infections DVT Meningitis
- 51. THANK YOU.