• Arata Horii, Takanori Saika, Atsuhiko Uno, Suetaka Nishiike, Kenji Mitani, Masato Nishimura, Tadashi Kitahara, Munehisa Fukushima, Aya Nakagawa, Chisako Masumura, Tomo Sasaki, Kaoru Kizawa, and Takeshi Kubo.
• Department of Otolaryngology, Osaka University Medical School, Japan. ahorii@ent.med.osaka-u.ac.jp
• Otol. Neurotol. 2006 Sep 1; 27 (6): 896-900.

ObjectiveTo look for factors relating to the vertigo control and hearing changes after intratympanic injections of gentamicin (GM).Study DesignProspective.SettingTertiary referral medical center.PatientsTwenty-eight patients with intractable Ménière's disease.InterventionsThree intratympanic injections of GM (once per day for three consecutive days).Main Outcome MeasuresAlthough five patients needed further GM injections or vestibular neurectomy because of poor control (Group I), 23 patients had their vertigo controlled for more than two years without further treatment (Group II). The number of vertigo spells per month, pure-tone audiometry, electrocochleography, caloric response, post-head shake nystagmus, and plasma vasopressin as a stress marker were examined.ResultsBefore GM injections, there was no difference in the number of vertigo spells per month between Groups I and II. However, the hearing thresholds were higher in Group I. Hearing improvement, increase in percentage of canal paresis and induction of post-head shake nystagmus were observed after GM injections only in Group II. Even in the 11 patients who showed an improvement in hearing of more than 10 dB (hearing improvement group), percentage of canal paresis was increased after GM. More, premedication plasma vasopressin levels were lower in the hearing improvement group as compared with the hearing loss/no changes group. Four of eight patients became negative for dominant negative summating potential in electrocochleography after GM injections in the hearing improvement group.ConclusionOur data indicate that the frequency of vertigo is not a key factor in the vertigo control after GM injections, that induction of vestibular damage in the injected ear is essential for the control of vertigo and this effect is mostly pronounced in patients with milder hearing loss, and that hearing improvement is not only a consequence of good vertigo control but also affected by the stress level before treatment.

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