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Gentamicin injections for Meniere disease: comparison of subjective and objective end points.

Abstract

This retrospective study reports the overall efficacy and comparative results of intratympanic gentamicin injections for disabling vertigo episodes. All patients received weekly injections for diagnosed Meniere disease. In Group 1 (81 patients), treatment end points were determined by subjective complaints of imbalance, with resolution of vertigo. In Group 2 (23 patients), treatment end points were determined when 2 or more values of nystagmus were demonstrated. (Group 2 patients were assessed before initiation of therapy for head-shaking, head- thrust, and spontaneous nystagmus using infrared video goggles.) After the final injection, all patients had audiograms and balance and oculomotor retraining. Gentamicin therapy was determined to be successful based on 3-month post-therapy findings of vertigo resolution, stable hearing, normalized nystagmus, and functional balance.

Introduction

French physician Prosper Meniere first described Meniere disease in 1861, and it remains a challenging entity that can vary from patient to patient and cause symptoms ranging from mild to disabling. In 1993, Harold F. Schuknecht commented at the Third International Symposium on Meniere's disease, "Here we are 132 years after Meniere, still agonizing on how to manage this unsavory disorder." (1)

The vertigo of Meniere disease is typically treated with a low-salt diet, diuretics, and labyrinthine suppressants. The general consensus is that this traditional medical management controls vertigo in about 80% of patients, although some investigators have reported only a 70% success rate. In 1997, Rauch and Oas at Massachusetts Eye and Ear Infirmary reported that 95% of their patients responded to traditional medical management. (2)

Fowler published a paper on streptomycin therapy for vertigo in 1948, (3) and intratympanic aminoglycoside treatment for vertigo has been used for more than 40 years. Intratympanic streptomycin therapy for the vertigo spells of Meniere disease was first described by Schuknecht in 1957. (4) He described his early use of intratympanic therapy as ablation therapy, whereby cochlear function was sacrificed. Today, streptomycin is not the drug of choice because of its limited availability, small therapeutic window, and related hearing loss.

Gentamicin is the drug of choice at present. It is readily available, has a large therapeutic window before reaching a cochleotoxic dosage, and causes less pain than streptomycin on injection, especially if it is buffered. In the last 10 years, intratympanic gentamicin has been used extensively to treat the intractable vertigo of unilateral Meniere disease. Numerous reports on gentamicin therapy relate successful reduction of vertigo without sacrificing cochlear function. A review across investigators, however, reveals no clear consensus on procedures. Delivery method, dosage, number of treatments and total dose, interval between treatments, and indicators for treatment cessation vary among investigators.

This study was undertaken to compare results and efficacy of gentamicin-injection therapy for Meniere disease using subjective and objective end points for duration of therapy. Comparison of end points may be important in determining the fewest gentamicin injections needed for effective therapy.

Patients and methods

All patients in this study had unilateral Meniere disease, as described by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery, (5) and intractable vertigo. Patients were divided into Group 1, in which end points were subjective (no complaints of vertigo attacks), and Group 2, in which end points were objective (head-shaking, head-thrust, spontaneous nystagmus measurements).

Pretreatment testing. All patients underwent otologic historytaking, physical examination, audiography, caloric testing (baseline warm only), and magnetic resonance imaging (to exclude a retrocochlear lesion) before the initial injection. Informed consent was obtained, with emphasis on the possibilities of severe imbalance approximately 4 days after the initial injection and hearing loss. Comprehensive audiologic evaluation, including pure tones and word-recognition testing, was performed before each treatment.

In Group 2, patients underwent vestibular testing for spontaneous nystagmus and testing for head-shaking and head-thrust nystagmus as described by Minor? Infrared videography was used for visual observation of nystagmus. The tests were administered before the first injection and each subsequent weekly injection.

Spontaneous nystagmus was tested by observing for right- or left-beating nystagmus present at rest. For head-shaking nystagmus, patients were asked to shake the head rapidly for 20 cycles while tilting it down at a 20[degrees] angle to align the horizontal canal. (7,8) They were then asked to stop abruptly and open their eyes. The presence and direction of nystagmus were recorded. For head-thrust nystagmus, patients were asked to maintain their gaze on a light in the infrared video goggles while the head was rotated side to side (passive method), slowly at first, then with a gradual increase in speed. Nystagmus was recorded in patients who had to readjust their gaze on the light.

Treatment method. A gentamicin concentration of 40 mg/ml buffered to pH 6.8 with a resulting concentration of 25.8 mg/ml was used. A small area of the tympanic membrane was anesthetized with phenol on a cotton applicator, and a myringotomy was performed to release the air ("beer can" principle). Enough gentamicin to fill the middle ear (0.2 to 0.3 ml) was injected through the myringotomy site and allowed to remain for 45 minutes (with the patient in the supine position). If additional gentamicin was needed to refill the middle ear, it was injected 20 minutes after the initial injection. Patients received treatments weekly until the subjective or objective end point was reached.

In Group 1, injections were stopped when patients reported cessation of vertigo attacks and/or when persistent unsteadiness developed.

In Group 2, injections were stopped when 2 or 3 objective measures of nystagmus were present. In patients with nystagmus before the first injection, measurements of change in amplitude or intensities of slow-phase nystagmus were used to determine cessation of injections. Of the 23 patients in Group 2, 6 (26%) demonstrated head-shaking nystagmus and 1 (4.3%) demonstrated spontaneous nystagmus before injections. The remaining 16 (69.6%) patients had no nystagmus prior to injections.

After the final gentamicin injection, all patients had vestibular therapy consisting of oculomotor exercises, balance retraining, and gait training to normalize vestibulo-ocular reflex and improve functional balance and mobility. They also had medical and audiologic follow-up 6 months after their last injection.

Results

Outcomes of successful therapy were resolution of vertigo, (5) normalization of vestibulo-ocular reflex, and normalization of functional balance. These findings at 3-month follow-up, along with findings on changes in hearing sensitivity, are summarized in the table.

Hearing outcomes. Hearing sensitivity, as defined by the 1995 criteria of the American Academy of Otolaryngology-Head and Neck Surgery, (5) was improved after intratympanic gentamicin injections in 22% of Group 1 patients. The average improvement was 20 dB hearing threshold level (HTL) in pure-tone and 36% in word-recognition scores. In 35%, hearing became worse after treatment; average decreases were 23 dB HTL in pure-tone and 44% in word-recognition scores. In 43% of patients, hearing was unchanged.

In Group 2 patients, hearing was improved in 31% by an average of 15 dB HTL in pure-tone and 37% in word-recognition scores. In the 17% in whom hearing became worse, the average decrease in pure tones was 25 dB HTL and in word recognition it was 30%. Hearing was unchanged in 52% of patients.

Differences in hearing results were not statistically significant according to chi-square analysis and 2-sample tests (6) for differences in pure tones and word recognition. Also, the natural fluctuations in hearing that accompany Meniere disease must be considered. The important point is that 65% in Group 1 and 83% in Group 2 had either stable or improved hearing sensitivity. Profound hearing loss developed after treatment in only 1 patient, who had severe hearing loss at initiation of treatment.

Recurrence. After 6 months, the observed recurrence rate of Meniere vertigo in Group 1 was 24.69%. The 20 patients with recurrence required additional gentamicin injections, plus vestibular neurectomy in 2 of them and transmastoid labyrinthectomy for persistent vertigo attacks in 1.

Group 2 had an observed recurrence rate of only 8.7%. Of the 2 patients with recurrence, 1 required additional gentamicin injections and 1 required transmastoid labyrinthectomy for persistent vertigo attacks.

Complications. We encountered few complications. A small percentage of patients in each group had hearing loss after treatment, but the significance of this result is difficult to assess because of the natural fluctuations in hearing with Meniere disease. A similar number of patients had improved hearing. Imbalance after intratympanic gentamicin is common and is usually controlled with vestibular therapy. Neither persistent tympanic perforation nor otitis media was observed following treatments. Failure rates were low in both groups and were usually controlled with additional injections.

Discussion

Intratympanic gentamicin injections, in our experience, have nearly eliminated the need for vestibular neurectomy and labyrinthectomy. A few years ago, we were performing an average of 12 vestibular neurectomies per year, but during the 5 years since we started using intratympanic gentamicin for intractable vertigo of Meniere disease, we have performed only 2. In patients with severe hearing loss and poor word discrimination who do not respond to gentamicin therapy, transmastoid labyrinthectomy is our treatment of choice.

Early in our experience with intratympanic gentamicin, we did warm caloric testing before each treatment. It soon became evident, however, using the protocol previously described, that vestibular function as tested by calorics underwent little change. Infrared videography and head-shaking nystagmus testing appear to be more efficient in evaluating the subtle changes in vestibular function following intratympanic gentamicin therapy. In our study, the vestibulo-ocular reflex typically normalized within 3 months of vestibular therapy and post-therapy oculomotor exercises.

Results of this study support the efficacy of intratympanic gentamicin injections for eliminating intractable vertigo episodes in Meniere disease. Comparison of subjective and objective end points indicates no significant differences in outcome of the two groups in terms of eliminating vertigo and stabilizing hearing sensitivity. Fewer gentamicin treatments may be needed, however, when objective measurements of nystagmus are used to determine therapy end points. Differences in recurrence rate were only marginally significant (p = 0.0798) because of the study's small sample size.

Acknowledgments

We wish to thank Julie Shephard, MA; Dana Heath, MS; Kimberly Oviedo,AuD; Peggy Marbach, OTD; and Janie Barnabei, OTR, for their assistance.

References

(1.) Schuknecht HF. Introduction. In: Filipo R, Barbara M. Meniere's Disease: Perspectives in the '90s: Proceedings of the Third International Symposium, Rome, Italy, October 20-23, 1993. Amsterdam: Kugler Publications; 1994:1-5.

(2.) Rauch SD, Oas JG. Intratympanic gentamicin for treatment of intractable Meniere's disease: A preliminary report. Laryngoscope 1997;107(1):49-55.

(3.) Fowler EP. Streptomycin treatment of vertigo. Transactions of the American Academy of Ophthalmology and Otolaryngology 1948; 52:239-301.

(4.) Schuknecht HF. Ablation therapy in the management of Meniere's disease. Acta Otolaryngol Suppl 1957;132:1-42.

(5.) Committee on Hearing and Equilibrium guidelines for the diagnosis and evaluation of therapy in Meniere's disease. American Academy of Otolaryngology-Head and Neck Foundation, Inc. Otolaryngol Head Neck Surg 1995;113(3):181-5.

(6.) Minor LB. Intratympanic gentamicin for control of vertigo in Meniere's disease: Vestibular signs that specify completion of therapy. Am J Otol 1999;20(2):209-19.

(7.) Hain TC, Fetter M, Zee DS. Head-shaking nystagmus in patients with unilateral peripheral vestibular lesions. Am J Otolaryngol 1987; 8(1):36-47.

(8.) Hain TC, Spindler I. Head-shaking nystagmus. In: Electronystagmography Report Archives 1983-1999. Schaumburg, Ill.: ICS Medical; 2000:77-80.

Ronald Leif Steenerson, MD; Robin B. Hardin, MA; Gaye W. Cronin, OTD

From the Atlanta Ear Clinic, Atlanta, Georgia.

Corresponding author: Ronald Leif Steenerson, MD, Atlanta Ear Clinic, 980 Johnson Ferry Rd., Suite 470, Atlanta, GA 30342. Phone: (404) 851-9093; fax: (404) 851-9097; e-mail: earclinic@mindspring.com
Table. Results at 3 months after intratympanic gentamicin
injections to treat Meniere disease

 Group 1: Group 2:
 Subjective end Objective end
 points (n = 81) points (n =23)

Patient demographics
Female:male 49:32 13:10
Age range (median) 30-80 yr (53 yr) 24-71 yr (48 yr)
Average time from 8 yr 4.3 yr
 symptom onset

Treatment
Time period 5/1997-11/2000 11/2000-3/2002
No. injections 1-9 (4) 1-3 (2)
 (average)

Results
Vertigo resolved 96% 97%
Vestibulo-ocular 96% 97%
 reflex normalized
Functional balance 100% 100%
 normalized
Hearing sensitivity 65% 83%
 stable or improved
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Article Details
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Title Annotation:ORIGINAL ARTICLE
Author:Steenerson, Ronald Leif; Hardin, Robin B.; Cronin, Gaye W.
Publication:Ear, Nose and Throat Journal
Article Type:Clinical report
Geographic Code:1USA
Date:Aug 1, 2008
Words:2002
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