Current role of transtympanic gentamicin therapy in the management of unilateral meniere’s disease
K. K. Desarda1, D. A. Bhisegaonkar 2
Abstract: Transtympanic gentamicin infusion is an alternative to surgical labyrinthectomy and Vestibular nerve section for the treatment of refractory vertigo associated with Meniere’s Gentamicin, the current drug of choice provides excellent vertigo control and is a less Invasive method to destroy the vestibular labyrinth. The goal of the treatment is to Eliminate the abnormal vestibular inputs from the vestibular inputs from the diseased ear Without adversely affecting the hearing. It’s salutary effect results from the damage of Both the sensory neuroepithelium and the dark cells of the labyrinth. Intratympanic Gentamicin may cause s. n. hearing loss In some patients {10–15%}. Despite this s. n. Loss, results are encouraging. 50 cases of unilateral Meniere’s disease were treated at KEM hospital, Pune, during 1996 to 2002 with the follow–up of 2 to 4 yrs. All cases were infused with gentamicin transtympanically for 4 to 6 weeks. N weekly basis with other surgical treatments are obviated by this treatment. This prospective study of gentamicin infusion revealed high success rate of controlling vertigo in about 92% patients. This treatment modality offers a less invasive but effective option for treating refractory vertigo of Meniere’s disease.

Key words: Gentamicin, Meniere’s, chemical labyrinthectomy, micro wick

Introduction
Meniere’s disease is a clinical disorder characterized by acute episodes of vertigo, fluctuating hearing loss, aural fullness & tinnitus2. 80% patients of Meniere’s disease are treated successfully by medical treatment. Remaining 20% who have failed medical treatment need either surgical or chemical ablation of vestibular function. Surgical procedures designed to prevent endolymphatic hydrops such as cochleostomy, endolymphatic sac shunt are falling out of favour due to high incidence of sensorineural hearing loss (20–30%). Vestibular nerve section, although very effective is a difficult surgery with significant morbidity and not uncommon complications

Schucknecht (1957) introduced transtympanic mode of Delivery with streptomycin4 & Beck Schmidt (1978) first used gentamicin by the Transtympamnic route5 for treating Meniere’s disease and proved the efficacy of the gentamycin infusion. The success rate was 92–100%2,4,5,6. This prospective study of 50 patients of unilateral Meniere’s disease in KEM hospital, Pune, during 1996–2002 revealed that intratympanic gentamicin therapy has a success rate of controlling vertigo in 92% with S. N. loss in 10–15% of the cases. This being a safe, less invasive and readily accepted treatment modality was the choice of treatment in controlling refractory vertigo of Meniere’s disease. The intratympanic gentamicin infusion (40mg/ml) buffered with 7.5% sodium bicarbonate solution was used slowly over a 10 minutes period. We have recorded our observations and post infusion results for over six years and found that gentamicin therapy is an ideal option to surgical labyrinthectomy. The ease with which gentamicin can be obtained and apparently lower incidence of its cochleotoxic side–effect has currently made it the preferred aminoglycoside for chemical treatment of Meniere’s disease.

Materials & methods:
(TABLE I, II, III)
50cases of 32 males & 18 females within age group Of 30–70 years of proved unilateral Meniere’s disease were treated with repeated transtympanic gentamicin infusion through the grommet for 4–6 weeks on weekly basis During the study, we have excluded CSOM., acoustic neuroma, acoustic trauma, barotraumas, diabetes, hypertension, cervical spondylosis & anaemia with the relevant investigations. Only unilateral Meniere’s disease cases were included in the study group. Prior to infusion, all patients were subjected to routine investigation such as PT Audiometry, Tone decay, SISI, caloric tests, MRI. brain especially for internal auditory meatus and posterior cranial fossa and all relevant biochemical tests. All 50 cases were given medical treatment for at least 3 months prior to gentamicin infusion therapy. The treatment includes diuretics, vasodilators, labyrinthine sedatives, antiallergics and steroids.

All cases were also informed about the side effects of this treatment such as sensorineural hearing loss in 10–15%, ataxia lasting for 4–6 weeks and imbalance until central compensatory mechanisms take over and the need for the head and neck Catwhorne Cooksey’s exercises after the treatment end–point. The infusion of gentamicin 40 mg/ml was used with dilution with 7.5% sodium bicarbonate solution. 10mg/ml gentamicin was slowly infused intratympanically by poster inferior quadrant myringotomy with grommet insertion.

The study ear was elevated by 45 degrees and infusion continued slowly over 10 minutes. The patient maintained the supine position with the study ear above for about 45 minutes post–infusion in the recovery room. The infusions were administered on weekly basis for 4–6 wks. Depending on clinical response in controlling vertigo. The end point of the treatment was total relief from vertigo and associated symptoms. The morbidity of unsteadiness/dysequilibrium, S.N. loss and the appearance of spontaneous nystagmus were cardinal signs of the efficacy of the gentamicin infusion.

Table I: Age distribution:

Age group (years)	No. of cases
30–40 41–50 51–60 61–70 Total	06 13 22 09 50

Table II – The sex ratio:

Sex	No. of cases
Male Female Total	32 18 50

Table III – Transtympanic infusions required:

No. of Infusions	Cases
1–2 3–4 5–6 Total	10 23 17 50

The results (As per guidelines of AAO–HNS, 1985) 7:
Table IV: Vertigo Relief (n=50)

Vertigo control	No. of patients	Percentage
Complete	36	72
Substantial	10	20
Limited	02	04
Insignificant	02	04
Worse	00	00

Table V: Hearing loss (n=50)

Hearing loss	No. of patients	Percentage
Worsened	05	10
Unchanged	37	74
Improved	08	16

Table VI : Tinnitus control (n=50)

Tinnitus control	No. of patients	Percentage
Absent	09	18
Improved	36	72
Unchanged	05	10

Table VII: Aural Fullness Control (n=50)

Aural Fullness Control	No. of patients	Percentage
Absent	31	62
Improved	19	38
Unchanged	00	00

Table VIII : Post Treatment Caloric Response

Post Treatment Caloric Response	No. of patients	Percentage
No. response	36	72
Poor response	10	20
No. Change	04	08

Table IX: Comparison of Results

	Vertigo Control	Hearing Loss
Beck & Schmidt (1978)5	95%	15%
Odkivist (1988) 8	95%	22%
Nedzelski (1993) 9	100%	37%
Lorne (1993) 10	100%	41%
Susanne & Pyykko (1995) 11	90%	32%
KEM Hospital Pune, Study (KKD)	92%	15%

It was observed that 4–6 wks period was taken to achieve excellent vertigo control. Post infusion audio vestibular tests were done in all cases to record the observations and results.