Vestibular Schwannoma - Case Discussion

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  •  A 50 year old male patient presented with 
  1.     Progressive hearing loss for 3 months
  2.     Tinnitus for 2 months.
  3.     Ataxia for 1 month


Nect axial images show a heterogenous predominantly isodense mass in the left CP angle causing mass effect on 4th ventricle  
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The lesion is noted to bulge into Porus acoustics which appears mildly dilated
T1 weighted axial Sagittal and coronal MR images shows an extraaxial  homogenously enhancing mass lesion in the left Cerebello pontine angle causing mass effect on the 4th ventricle leading to hydrocephalus and mass effect on the middle cerebral peduncle 




Vestibular Schwannoma

They are benign tumours. They are the most common internal auditory canal/ cerebellopontine angle cistern tumours and second most common extra axial neoplasm in adults. VS most commonly involve the inferior vestibular nerve and classically arise at Porus acusticus.

 Clinical features


Most often asymptotic, Sensorineural hearing loss, tinnitus, disequilibrium or facial nerve palsy. Bilateral VS is seen in nf2


Imaging 



MRI has better sensitivity than CT in detecting these tumours. Classic MR features include a cylindrical shaped (small lesion) or ice cream cone shaped (larger lesion) with T2  hyperintense signal and avid enhancement. They enlarge and they can extend into posterior fossa causing mass effect on brain stem or hydrocephalus. Typically the border of VS forms acute angle with temporal bone



Surgical approach 

  1. Middle cranial fossa - for intracanalicular lesion less the 1 cm CPA extension, increased risk of facial nerve palsy 
  2. Suboccipital approach - lesion with greater CPA extension, can preserve hearing function but has limited access into lateral IAC and is prone to CSF leak.
  3. Translabyrinthine approach - patients who have lost hearing function, but it offers lowest recurrence rates.

Differential diagnosis 

  •        Meningioma - broad dural base
  •        Epidermoid- very high signal intensity on diffusion weighted images, non enhancing lesion
  •        Facial nerve Schwannoma - Can mimic VS if confined to IAC without involvement of    geniculate ganglion or labyrinthine segment of facial nerve 



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