PATTERNS OF HEARING-LOSS IN NONEXPLOSIVE BLAST INJURY OF THE EAR

A prospective study of hearing loss in 120 cases with non-explosive bl ast injury of the ear, gathered over a six-year period, is presented. Thirty-three (27.5 per cent) patients had normal hearing, 57 (47.5 per cent) conductive hearing loss, 29 (24.2 per cent) mixed loss and one (0.8 per cent) had pure sensorineural loss. The severity of conductive hearing loss correlated with the size of the eardrum perforation; onl y a marginal difference was found between water and air pressure injur ies, with respect to this type of hearing loss. Of all locations, perf orations involving the posterior-inferior quadrant of the eardrum were associated with the largest air-bone gap. Audiometric assessment reve aled that none of the patients suffered ossicular chain damage. Three patterns of sensorineural hearing loss were identified: a dip at a sin gle frequency, two separate dips, and abnormality of bone conduction i n several adjacent high frequencies. Involvement of several frequencie s was associated with a more severe hearing loss than a dip in a singl e frequency. Healing of the perforation was always accompanied by clos ure of the air-bone gap, while the recovery of the sensorineural heari ng loss was less favourable.