Different clinical characteristics of aminoglycoside-induced profound deafness with and without the 1555 A -> G mitochondrial mutation

Recent genetic studies have shown that hereditary susceptibility to aminogl ycoside antibiotics is caused by the 1555 A-->G mitochondrial mutation. We found the 1555 mutation in 4 out of 68 postlingual deaf patients who were c andidates for cochlear implantation. All 4 patients developed bilateral pro found hearing loss following administration of aminoglycosides. The pedigre e of the family shows exclusively maternal transmission of hearing impairme nt in each case. On comparison with neurootological findings from aminoglyc oside-induced deaf patients without the 1555 mutation, four distinct charac teristics were noted: (1) a progressive nature of hearing loss, (2) better residual pure-tone thresholds; (3) lower thresholds for electrical promonto ry stimulation, and (4) well-preserved vestibular function. Although other factors such as differing dosages and/or administration routes may also be involved, profound hearing loss associated with the 1555 mutation may be du e to a different pathogenic mechanism, i.e., strial dysfunction rather than a direct insult to the hair cells. Copyright (C) 2001 S. Karger AG. Basel.