Incidence and risk of cochleotoxicity and vestibulotoxicity in patients with haematological malignancies

The risk of ototoxicity accompanying therapeutic use of aminoglycosides is clinically well recognised. However, detailed description of the incidence, degree, severity and specific patient group risk is usually poorly documented. The aim of this project was to establish the incidence and risk of ototoxicity in patients with haematological malignancies recruited during follow up within the Haematology Department at Leicester Royal Infirmary. A total of fifty patients treated for haematological malignancies were recruited; 33 who had received aminoglycoside therapy as part of their treatment and 17 who had not. Following a comprehensive review of medical history for other potential causes of hearing loss or balance disturbance, patients were then tested with: standard pure tone audiometry (PTA); high frequency pure tone audiometry (HFPTA); distortion product otoacoustic emissions (DPOAEs); computerized dynamic posturography (CDP). There was a considerable incidence of noise exposure in both treatment groups. After accounting for this, the aminoglycoside treated group PTAs returned an incidence of cochleotoxicity of 4/33 or 12%. With HFPTA, there was evidence of hearing loss in the high frequency range for both the non aminoglycoside and the aminoglycoside treated groups. The loss was more marked for the aminoglycoside treated patients. The DPOAE results were interpreted alongside the PTA results and revealed evidence of mixed sites of damage at the cochlear outer hair cells and at a secondary site at the cochlear inner hair cells and/or cochlear nerve. The CDP results returned unexpected and highly significant evidence of mixed contribution to postural control performance deficit in the visuo-vestibular system with equivalent incidence in both treatment groups. None of the above findings showed any correlation with the comparatively low exposures to aminoglycosides or to any of the other drugs these patients may have received. The PTA and DPOAE findings are novel providing physiological evidence of involvement at the inner hair cells/cochlear nerve. The evidence from the HFPTA and CDP studies is considered to reflect potential non specific broad toxic effects due to disease/other therapeutics effects manifest in the cochlea and vestibular apparatus.