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Vestibular Schwannoma (Acoustic Neuroma)

  1. Definition:
    Vestibular schwannoma is a benign tumor of the cerebellopontine angle and arises most commonly from the Schwann cells of inferior vestibular nerve and can also arises from the superior vestibular nerve Commonest CPA angle tumor (80% of CPA angle tumors and 10% brain tumors)
  2. Features:                                                                           
    1. Slow-growing tumor (2mm/yr)
    2. Encapsulated
    3. Male: Female =1:1 (occurs in 20-30 yrs of age when the tumour is found in association with Neurofibromatosis type 2)
    4. Tumour is RADIORES1STANT     
  3. Clinical symptoms:
    1. Stage I (Otological stage):
      Tumours intrameatal and extrameatal upto 2cm
      1. U/L, gradually progressive sensorineural type of hearing loss
      2. U/L dip in the audiogram at 4 KHz
      3. Poor speech discrimination
      4. Vertigo
      5. Facial nerve involvement (sensory part)  Hitzelberger sign: anaesthesia over posterior, superior external auditing meatar and canal (dry irritating eyes, excessive tearing)
    2. Stage 2 ( Trigeminal nerve involvement)
      1. When tumor >2 cm extrameatally
      2. Pain, tingling and numbness along the distribution of trigeminal nerve
    3. Stage 3 (Brain stem and cerebellar compression)
    4. Stage 4 (Increasing intracranial pressure)
    5. Stage 5 (Terminal stage)                          
      1. Herniation of cerebellar tonsils               
      2. Failure of the vital centers in the brain stem
  4. Signs:
    1. Ear: Otoscopic finding: normal
    2. Cranial nerves:                                    
      V Nerve: Corneal reflex get impaired
      1. Motor functions are rarely affected
        VII Nerve; Inability to bury the eyelashes on the affected side
      2. Hitselberger’s sign: Loss of sensation in the postero-superior aspect to the external auditory canal because of facial nerve involvement.
        IX, X Nerve; Palatal, pharyngeal, and laryngeal paralysis
    3. Eyes: Nystagmus may be seen
    4. Cerebellar signs

Extra Edge: Earliest symptoms of acoustic neuroma is loss of hearing but most common presentation is loss of corneal reflex.

  1. Investigation:
    1. Audiometric evaluation
    2. Brainstem evoked response Audiometry
      1. Accuracy in diagnosis > 90%
      2. Increased interaural latency difference of wave V (N) = 0.2 msec)
      3. Increased interpeak interval of wave 1-V ((N) = 4 msec)
    3. Caloric Testing:
      1. Response may be normal if tumor small       
      2. May be diminished
      3. Suggestive finding: Significant reduction in the response in the absence of a history of dizziness.

Extra Edge. Recruitment is an abnormal growth in loudness and is seen in cochlear lesions.


Extra Edge. Tone decay, also called auditory fatigue, is change in auditory threshold when a continuous tone is presented to the ear. It is seen in acoustic neuroma and other retrocochlear lesions.



Extra Edge: Roll - Over curve may be seen.

  1. Radiological Tests:
    1. Plain X-rays : Best view; Perorbital view
      Difference of 1 mm in the vertical height of the internal auditory meatus is considered to be significant.
    2. C.T. Scan
      Cannot detect the intrameatal tumors
    3. MRI: gold standard for imaging vestibular schwannoma
      Gd DTPA: With the use of this paramagnetic enhancing substance tumors as small as 2mm can be picked
  2. Differential Diagnosis:
  1. Meniere’s disease                                        
  2. Meningioma - 2nd most common C.P. angle tumor    
  3. Primary cholesteatoma                               
  4. Arachnoid cyst
  5. Choroid plexus papilloma                           
  6. Facial neuroma
  7. Glomus jugulare
  1. Treatment:
    1. Surgical techniques:
      1. Approaches:
        1. Middle cranial fossa approach :
          • For small tumors with serviceable hearing
          • Advantage: Preserves hearing                    
          • Disadvantage:
          • VII nerve may get injured                    
          • Temporal lobe retraction lead to epilepsy            
        2. Trans labyrinthine approach                                        
          • Advantage: VII nerve identification is easy                
          • Disadvantage: Hearing is lost                              
        3. Retrosigmoid/ subocciptical approach:          
          • Advantage: Can remove big tumors                                               
          • Disadvantage: Cererbellar retraction: Cerebellar signs post operatively                             
        4. Combined Translabyrinthine- suboccipilal approach

P. S.
Serviceable hearing:
If hearing has to be saved in the affected ear, the interaural difference should be 30 dB with maximum speech discrimination score of 70%.


  1. Stereotactic radiosurgery / Gamma knife (radiation is delivered with Co-60)                                                                     
    1. Advantage:
      1. No morbidity of surgery
      2. VII nerve functions preserved
      3. Hearing preserved
    2. Disadvantage;                         
      1. Long term follow up and repeated radiological ly investigation since there is uncertainty about the biological behaviors of the tumor remnant

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