HSC Section 8_April 2017

TABLE III. Summary of Patients Undergoing Labyrinthectomies and Vestibular Neurectomies.

Pt

CP Before ITG

CP After ITG

CP After ETG

Class*

Dx

Comments

Labyrinthectomy 1 STP †

1

75%

–

No ETG

A

MD

83% (3 inj ‡ )

2

77%

No ETG

A

EH

Labyrinthectomy (intralabyrinthine schwannoma)

28% (3 inj ‡ ) 31% (3 inj ‡ ) 89% (4 inj ‡ )

3

15%

32%

A

EH

Labyrinthectomy

4

4%

29%

A

MD

Labyrinthectomy

5

44%

No ETG

A

MD

Vestibular neurectomy

*Functional classification according to the 1995 American Academy of Otolaryngology–Head and Neck Surgery guideline. † Surgery to control chronic otitis media. ‡ Number of intratympanic injections of gentamicin. CP 5 canal paresis on bithermal caloric test; Dx 5 diagnosis; EH 5 secondary endolymphatic hydrops; ETG 5 exploratory tympanotomy and gentamicin application; ITG 5 intratympanic gentamicin injection; MD 5 definite Menie` re’s disease; Pt 5 patient; STP 5 subtotal petrosectomy.

Vestibular neurectomy via middle fossa approach was performed in one patient to control intractable ver- tigo, even after successful ablation of vestibular function on a caloric test (canal paresis: 89%) with five rounds of intratympanic gentamicin injections. The hearing of the 52-year-old woman after ITG was still acceptable (36.25 dB of pure tone average, with 82% for speech discrimi- nation in the audiometry taken on a day prior to the surgery). After surgery, complete control of vertigo (class A) was achieved and hearing threshold was 35 dB after surgery. However, the hearing was progressively wors- ened to 55 dB after 1 year 6 months postoperatively, which was comparable with the worst hearing (53.75 dB) during 6 months prior to the surgery. Hearing Outcomes Overall, there was no significant change in hearing thresholds with the mean pure tone average 59.7 dB prior to ITG and 63.2 dB after ITG ( P 5 0.343, Student’s t-test). In total, 80 (84.2%) patients showed less than 10 dB change in hearing after ITG; hearing was improved more than 10 dB even after ITG in six (6.3%) patients; and three of them improved by more than 20 dB. Five of the six patients with hearing improvement achieved suc- cessful ablation of vestibular function on bithermal caloric test, and all of them did not show hearing fluctu- ation thereafter. In contrast, a patient with initially impaired vestibular reflex showed fluctuation of hearing with temporary hearing improvement at the point of assessment according to the 1995 AAO–HNS guideline. Two of the six patients experienced hearing aggravation in the proximity of the ITG, with the worsening of ver- tigo including the patient with hearing fluctuation. A total of eight (8.4%) patients experienced more than a 10 dB worsening of hearing levels. Four of the eight patients received more than three rounds of ITG; and 2.6 injections were applied, on average, in the eight patients. However, a careful review of the data revealed that most hearing loss took place after one (4 patients) or two (2 patients) injection(s), and only two patients experienced hearing loss after three injections. We com- pared the results of hearing changes with the success of ablation and the preoperative vestibular status, but nei- ther showed a statistically significant difference ( P 5 1.00 and 0.54, respectively, Fischer’s exact test).

Bilateral Progression of Menie`re’s Disease After ITG Two patients progressed to bilateral Menie`re’s dis- ease after ITG. Both of them developed vertigo with aggravation of hearing on the other side. The hearing levels of the injected side were already worse than 60 dB HL prior to ITG and were not aggravated after injection in both patients. Physical examination and the caloric test revealed apparently successful ablation of vestibular function on the injected side. One patient developed con- tralateral Menie`re’s disease at 2 years after ITG, and the other patient developed it at 5 years after ITG. DISCUSSION Previously, the effectiveness of ITG was commonly highlighted, with little discussion of its limitation. 7–12 The reason for failure is important because there could be some substantial limitation to drug passage through the round window membrane. In previous studies, mark- edly limited permeability or impermeability was reported in approximately 20% of cases. 16 In another study that directly visualized the passage of gadolinium injected into the tympanic cavity into the inner ear, 13% showed poor drug passage through the round window membrane, with 5% of cases showing no permeability. 17 This is very similar to our failure rate for ITG. The tympanum was inspected for any possible ana- tomical barrier around the oval window and/or the round window membrane that might limit the access of gentamicin. However, no obvious barrier such as muco- sal folds, mucosal thickening, or bone chips was evident, except a prominent bony overhang over the round win- dow in two patients. Such a prominent bony overhang could be a possible reason for the failure of ITG, accord- ing to a previous report, 14 because vestibular function was attenuated substantially and recurrent vertigo attacks were controlled after ETG in a patient. However, the reasons for the failure, especially in the two cases who needed additional labyrinthectomy, remain unclear. The permeability of the round window membrane is determined by several factors, such as the thickness of the membrane, the size of the particles, concentration, liposolubility, and electrical charge. 18 Considering that most of the listed variables were almost identical

Laryngoscope 125: April 2015

Rah et al.: Intractable Menie` re’s Disease

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