Inner Ear Perfusion

Inner Ear Perfusion

Elizabeth H. Toh

Inner ear perfusion refers to the administration of drugs through the tympanic membrane into the middle ear for absorption into the inner ear through the round window membrane. It has become increasingly popular as a treatment modality for a variety of inner ear disorders, offering the theoretical advantages of:

Direct delivery of medication to the diseased ear, thus avoiding effects on the contralateral ear and potential side effects of systemic therapy
Higher perilymph concentration of the medication
Minimally invasive, office-based administration of treatment

The most commonly used drugs for this form of treat include aminoglycosides and steroids. Intratympanic injection of other drugs for a variety of inner ear disorders remains controversial and is therefore not discussed in this chapter.

♦ Intratympanic Aminoglycosides

Indication for treatment Control of recurrent episodic vertigo in unilateral Meniere’s disease despite maximal medical therapy

Treatment principle Partial or complete chemical vestibular ablation. The ability to titrate treatment based on clinical symptoms is a distinct advantage of this treatment relative to surgical vestibular ablation. The disadvantages include difficulty in predicting duration of treatment, potentially higher risk of sensorinerual hearing loss, and variable outcomes. The variable course of Meniere’s disease complicates direct comparison of surgical and chemical vestibular ablation outcomes.

Drugs used Most commonly used drugs include gentamicin and streptomycin, both of which are preferentially vestibulotoxic. The availability of streptomycin in the United States at this time is restricted. Gentamicin is currently the preferred drug.
Dosage Gentamicin 30 mg/mL is compounded on the day of treatment; 1.5 mL of commercially available gentamicin for injection (40 mg/mL) is buffered with 0.5 mL of 0.6 M sodium bicarbonate, to reduce pain on injection.
Treatment protocol This varies by surgeon but is most commonly administered as a single injection and titrated by symptoms thereafter, or as a predetermined number of injections at weekly intervals. Prolonging the interval between injections and minimizing the total number of injections reduce the risk of hearing loss.
Treatment end point Disequilibrium is usually experienced 2 to 3 days after the injection and may continue for a variable period after treatment. The goal of treatment is elimination of vertigo attacks. This may be achieved at the expense of long-term disequilibrium. Complete vestibular ablation (measured by absent caloric responses in the injected ear) is no longer the end point of therapy. Treatment should be titrated to the patient’s clinical symptoms and discontinued when no further vertigo attacks are experienced or hearing deterioration is noted.
Complications The most common complication is hearing loss. Others include tympanic membrane perforation, infection, drug sensitivity, and bleeding.
Results Vertigo control in up to 90%. Risk of hearing loss in up to 30%.

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Tags: Otolaryngology a surgerial notebook

Jun 14, 2016 | Posted by admin in OTOLARYNGOLOGY | Comments Off

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Inner Ear Perfusion