Technical note on microcatheter implantation for local inner ear drug delivery: surgical technique and safety aspects.

HYPOTHESIS: Despite its invasiveness, the temporary implantation of a microcatheter into the middle ear cavity is an appropriately safe method for providing continuous drug delivery to the inner ear. BACKGROUND: For the application of drugs to the inner ear, different delivery strategies are available ranging from intratympanic injections to temporarily implanted microcatheters. It has recently been demonstrated that the choice of the drug delivery system influences the pharmacokinetics in the inner ear. If a continuous drug application over several weeks is required, a secure placement of the delivery device (i.e., the microcatheter) is necessary to guarantee efficient drug delivery and to avoid unwanted side effects. STUDY DESIGN: Retrospective chart review. MATERIALS AND METHODS: During 2000 to 2005, 25 patients with acute unilateral severe-to-profound hearing loss or anacusis and failure of systemic high-dose glucocorticoid and rheological therapy were offered an intratympanic delivery of glucocorticoids via a temporarily implanted catheter and an external pump for up to 4 weeks as a salvage treatment option. The standardized surgical implantation and fixation technique developed for the microcatheter were characterized by six elements: 1) a medial and a lateral tunnel connected by a groove in the posterior wall of the bony ear canal, 2) stabilization of the catheter with bone wax and soft tissue plugs in the tunnels, 3) an ear canal packing, 4) a series of fixating sutures along the catheter, 5) an adhesive dressing, and 6) additional tapes at the connecting line between pump and catheter. At the end of the implantation period, the catheter was removed by a second surgical procedure allowing for evaluation of the catheter position and the condition of the middle ear space. RESULTS: Adverse events included catheter dislocation, catheter obstruction, formation of mild granulation tissue in the middle ear cavity, tympanic membrane defects, and ear canal skin defects. With introduction of an improved implantation and fixation technique, the number of catheter dislocations could be significantly reduced. No complications were observed on long-term follow-up. CONCLUSION: If the pharmacokinetics or pharmacodynamics of a specific local inner ear therapy approach requires a continuous intratympanic drug application (e.g., to restore hearing in patients with severe or profound hearing loss), the temporary implantation of a microcatheter by a standardized surgical technique is a feasible and appropriately safe method for providing continuous drug delivery to the inner ear.