Clinical Predictors of Streptomycin-Vestibulotoxicity

The Global tuberculosis control is challenged with a growing resistance to antitubercular treatment (ATT) culminating in resistant (MDR/XDR) strains; an important factor being premature withdrawal of streptomycin owing to its morbidity particularly nephrotoxicity and cochleotoxicity as guidelines for their prevention exist. An attempt is made here to address the least recognized and most debilitating vestibular toxic effects of streptomycin and defining a vestibular-protocol for its early detection and progression. Thirty two prospective patients (treatment-failures, relapse and default cases) undergoing ATT (24 shots of IM streptomycin 15-20 mg/kg over 8 weeks) underwent complete vestibular workup including vestibulo-ocular and vestibulo-spinal reflex assessment with an attempt to closely follow them. Four categories (I: No-, II: Occult-, III: Delayed-Manifest- and IV: Manifest-vestibulotoxicity) were defined. The DHI and casual gait abnormality clearly differentiated III/IV from I/II. The occilopsia and head thrust tests significantly differentiated II from I. Rotation and bithermal calorics significantly differentiated I from II and II from III/IV. The Fukuda, Rhomberg, Tandem-Rhomberg and CTSIB were significant in differentiating I from II and II from III/IV. Dix-Hallpike and Positional tests were of no significance in the entire study. The Occilopsia and Head-Thrust tests that showed 100 % positivity for II to IV are more likely to better predict 'manifest' or 'occult' -vestibulotoxicity while DHI and casual gait assessment may be carried out by a paramedic at a peripheral center to suspect vestibulotoxicity. Since we found absolute compliance with our series we feel that vestibulotoxicity may not be a deciding factor for termination of streptomycin provided an in-built mechanism for patient support/counseling be incorporated in management schedule.