[Use of the round window micro cath for inner ear therapy - results of a placebo-controlled, prospective study on chronic tinnitus].

The local therapy of inner ear diseases provides a means of directly applying pharmacological substances and delivering electrical stimulation to inner ear structures. Problems relating to dosage, systemic effects and the blood-cochlear barrier are thus avoided, which is not the case with systemic therapy. The preferred access point is the membrane of the round window. An appropriately shaped catheter (DURECT Corporation, Cupertino, CA, USA), whose double-lumen passage system permits the variation of concentration and flow, is inserted into the round window niche. In a prospective, placebo-controlled clinical study, this application system was tested in 20 patients with chronic tinnitus. Following implantation the substances lidocaine, glutamate, glutamic acid and caroverine were applied via an attached external micropump. The values for tinnitus loudness, level of irritation caused by the tinnitus and subjective effectiveness of the therapy - measured by means of the visual analog scale (VAS) - showed no significant change, although the most marked improvement was indicated for caroverine. These results indicate that a positive effect was observable only in a proportion of the patients. Continuous therapy of tinnitus and inner ear diseases will only be possible once a totally implantable microdosage system has been developed.