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Perilymphatic Fistula (PLF):
Applications of intratympanic therapy for vertigo: Intratympanic gentamicin therapy (ITGM) is an accepted treatment for medically refractory MD. The author has used this therapy with excellent vertigo control rates for patients with new-onset MD, previously treated MD, or MD that has recurred despite prior surgical therapy (3). The author has also used intratympanic therapy to successfully treat vertigo after perilymphatic fistula repair. Between July 1997 and February 2002, 44 patients with medically refractory vertigo were treated with ITGM, with a success rate of 95%, and an increased rate of sensorineural hearing loss of less than 5% (unpublished data). ITGM Protocol: The author’s needle puncture technique for delivering ITGM is as follows: A history, physical examination, appropriate imaging studies, baseline audiogram and electronystagmography are obtained. The patient must have refractory vertigo in one ear despite medical treatment. The patient is placed in a recumbent position with the treated ear upwards. The tympanic membrane is anesthetized with topical lidocaine/prilocaine cream (EMLA cream) for 10 to 15 minutes. This cream is suctioned and the middle ear is filled with 1 cc of buffered gentamicin solution, introduced through the tympanic membrane via a 25 gauge spinal needle on a 1-cc syringe. The patient is asked to avoid swallowing and kept supine for 30 minutes. At the end of this time, any remaining solution is suctioned from the ear canal and the patient is sent home. A follow-up appointment is scheduled in one month. If there is persistent vertigo at that time, another treatment is administered. The endpoint for treatment is control of vertigo. At times it might be necessary to delay injections due to hearing loss or ataxia. ITGM provides a selective chemical ablation of the ipsilateral vestibular end organ. Gentamicin is believed to work via decreasing production of endolymph, or via a direct toxic effect on type I vestibular hair cells (4). In general, gentamicin exerts its effect in a delayed fashion, beginning in three to five days. It is not clearly evident the duration of time over which the medication works, but the author believes the final result of an injection might be evidenced in three to four weeks. Most patients require 1-2 injections. All methods of ITGM have an excellent success rate, with vertigo control approaching approximately 85% (2). In summary, ITGM therapy for vertigo has an excellent vertigo control rate, can be administered in a clinic setting, and has few side effects. Differential diagnosis of sensorineural hearing loss: Sensorineural hearing loss (SNHL) has many causes. It is important to determine if the hearing loss is congenital, hereditary, sudden, chronic, or progressive. Presbycusis and noise exposure usually cause slow, progressive SNHL. Viral or bacterial infections, blunt and surgical trauma may precipitate sudden SNHL. Ototoxic medications may also cause sudden SNHL, but a slowly progressive hearing loss, secondary to ototoxic medications is possible too. Acoustic neuroma usually causes a slow progressive hearing loss with tinnitus and sometimes imbalance. When the etiology of SNHL cannot be determined, the term "idiopathic" has been used. Treatment of Sudden, Idiopathic SNHL: There is evidence that idiopathic SNHL is secondary to inflammation within the cochlear system, possibly secondary to viral infection. Steroids have known anti-inflammatory properties and have been advocated for treatment of sudden SNHL. Moskowitz et al (5) treated 36 patients with idiopathic sudden sensorineural hearing loss with dexamethasone (an anti-inflammatory synthetic gluco-corticoid, within the family of steroids) and found that using this medication resulted in hearing improvement. Other studies have also found steroids to be beneficial (6). Most studies advocate doses of steroid equivalent to 1 mg/kg/day of prednisone (an anti-inflammatory, synthetic gluco-corticoid) tapering over 10 to 14 days. However, in some cases there is no recovery (7). This author has used intratympanic dexamethasone delivered via a needle puncture technique and has found patients tire of coming back every 3-4 days for injections. Additionally, the success rate has been poor. . Conclusion: In conclusion, intratympanic therapy potentially has vast and varied application in the treatment of patients with inner ear disorders. Clearly this therapy is in its infancy, but preliminary results have been very encouraging. All hearing health care professionals should be aware that this therapy could have application for their patients with hearing loss, vertigo, and possibly tinnitus.
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