Comprehensive study of audiological evaluation of retrocochlear space occupying lesions.

Nisha, Neelambaran (2010) Comprehensive study of audiological evaluation of retrocochlear space occupying lesions. Masters thesis, Madras Medical College, Chennai.

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Abstract

Retrocochlear space occupying lesions can be a life threatening condition presenting in different stages ranging from subtle otologic symptoms to life endangering tonsillar herniation and death. The various retrocochlear space occupying lesions are Acoustic Schwannomas, Meningiomas, Epidermoid Cysts, Arachnoid Cysts, Schwannomas of the 5th, 7th, 9th, 10th or 11th cranial nerves, Hemangiomas, Lipomas or Dermoid Cysts. Of all these, Acoustic Schwannomas in the cerebellopontine angle constitute 60- 90%. Next in frequency are Meningiomas, Epidermoid Cysts and Arachnoid Cysts. Since these lesions are slow growing and initially may present with subtle clinical symptoms, the Otorhinologists must maintain a high index of suspicion and use appropriate audiologic , vestibular and radiographic studies to diagnose these lesions at the earliest stage. Since there is no single audiologic test to detect a retrocochlear lesion , the patient has to undergo a battery of tests which are Puretone Audiometry, Speech Audiometry, Special Tests and Brainstem Evoked Response Audiometry. Early diagnosis if made with these tests, is of advantage since it can limit surgical morbidity and facilitate Facial Nerve and hearing preservation.and can be applied in Community Otorhinology. This study is on the efficacy of various audiological tests in the detection of retrocochlear space occupying lesions. A high index of suspicion needs to be maintained when symptoms of unilateral hearing loss and tinnitus co-exist in a patient. The patient then has to undergo a battery of audiological tests to rule a retrocochlear lesion. The first line audiological investigation is the PureTone Audiometry, but which cannot differentiate a cochlear from a retrocochlear lesion. The speech audiometry and special tests (SISI, TDT, ABLB etc.) are useful in differentiating cochlear from retrocochlear lesions. They have limitations when it comes to patients with hearing loss more than 60 dB. The sensitivity of Brainstem Evoked Response Audiometry in detecting retrocochlear lesion is found to be 93% in this study, with an advantage of detecting the site of the lesion. This test also has limitations when it comes to patients with hearing loss more than 60dB. No audiological test is 100 % sensitive in detecting retrocochlear lesions but when applied together the chance of early detection is increased. The sensitivity of Gadolinium Enhanced Magnetic Resonance Imaging reaches almost 100%, thus leaving it as the gold standard investigation for diagnosis of the condition. Taking into account of the cost factor of Gadolinium enhanced Magnetic Resonance Imaging, it cannot be used as a screening test, whereas Brainstem Evoked Response Audiometry can be used to screen for retrocochlear space occupying lesions when there is a high index of suspicion.

Item Type: Thesis (Masters)
Uncontrolled Keywords: retrocochlear space occupying lesions; audiometry
Subjects: MEDICAL > Otorhinolaryngology
Depositing User: Devi S
Date Deposited: 04 Jul 2017 10:14
Last Modified: 04 Jul 2017 10:14
URI: http://repository-tnmgrmu.ac.in/id/eprint/909

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