investigations

Last reviewed 01/2018

In a patient suspected of having an acoustic neuroma, the following tests are of value:

  • neuro-otological:
    • pure tone audiometry - demonstrates unilateral sensorineural hearing loss
    • brainstem audiometry - to distinguish cochlear deafness from retrocochlear disease
    • o speech discrimination test (1)
    • caloric test - expect depressed or absent response

  • CT - need contrast since acoustic neuromas are often isodense:
    • intravenous iodinated water soluble contrast (1)
    • metrizemide contrast into the basal cisterns or intrathecal air run up to the cerebellopontine angle clearly identifies small acoustic neuromas

  • MRI - especially for small intracanalicular tumours. With gadolinium - DTPA enhancement, this test is very sensitive and may demonstrate lesions of 1-2 mm in diameter within the auditory canal
    • T2-weighted images
    • contrast enhanced T1-weighted images - the sensitivity is increased by the gadolinium-based contrast medium and it can demonstrate small neuromas and intralbyrinthine lesions (2)

  • tomography of the internal auditor meatus - if no CT/MRI

Reference:

  • (1) British association of otorhinolaryngologists 2002. Clinical effectiveness guidelines, Acoustic neuroma (vestibular schwannoma)
  • (2) Ramnarine Devindra, Whitfield Peter. Management of patients with vestibular schwannoma. ACNR 2005; 5(4).