The Degeneration of the Vestibular Efferent Neurons After Intratympanic Gentamicin Administration

Endolymphatic Duct and Sac Decompression: A New Life for an Old Technique

BACKGROUND

Ménière's disease is an inner ear disorder causing recurrent vertigo, hearing loss, and tinnitus. Diagnosis is based on the variability of the symptoms over time and absence of radiological abnormalities. Medical therapy is effective only in a small percentage of patients. Surgical strategies remain controversial. In this article, we revisit a surgical technique neglected over the years: endolymphatic sac surgery.

METHODS

Fifty-four patients affected by Ménière's disease underwent endolymphatic duct and sac decompression. According to the American Academy of Otolaryngology-Head and Neck Surgery criteria, vertigo control was evaluated with follow-up at 6 months, 1 year, and 2 years from the intervention. Hearing results were evaluated before the surgery and at 2 years of follow-up using the pure tone average. The results were compared with similar techniques of endolymphatic sac surgery described in the literature.

RESULTS

According to the American Academy of Otolaryngology-Head and Neck Surgery criteria classification, 2 years after surgery, 87% patients achieved complete control of vertigo (class A). The hearing remained stable in 93.5% of patients. The results appear compatible with other publications data regarding endolymphatic sac surgeries.

CONCLUSION

The duct and endolymphatic sac decompression allows the control of vertigo and preserves hearing from the pathological effects of Ménière's disease. The revised technique allows the functional restoration of endolymphatic homeostasis.

Contralateral spreading of substances following intratympanic nanoparticle-conjugated gentamicin injection in a rat model

This study was performed to investigate the Eustachian tube as a potential route for contralateral spreading following intratympanic nanoparticle (NP)-conjugated gentamicin injection in a rat model. Sprague–Dawley rats were divided into three groups and substances were injected in the right ear: group 1 (fluorescent magnetic nanoparticles [F-MNPs], n = 4), group 2 (F-MNP-conjugated gentamicin [F-MNP@GM], n = 2), and control group (no injections, n = 2). T2-weighted sequences corresponding to the regions of interest at 1, 2, and 3 h after intratympanic injection were evaluated, along with immunostaining fluorescence of both side cochlea. The heterogeneous signal intensity of F-MNPs and F-MNP@GM on T2-weighted images, observed in the ipsilateral tympanum, was also detected in the contralateral tympanum in 4 out of 6 rats, recapitulating fluorescent nanoparticles in the contralateral cochlear hair cells. Computational simulations demonstrate the contralateral spreading of particles by gravity force following intratympanic injection in a rat model. The diffusion rate of the contralateral spreading relies on the sizes and surface charges of particles. Collectively, the Eustachian tube could be a route for contralateral spreading following intratympanic injection. Caution should be taken when using the contralateral ear as a control study investigating inner-ear drug delivery through the transtympanic approach.

What is the efficacy of gentamicin on the incidence of vertigo attacks and hearing in patients with Meniere's disease compared with steroids? A meta-analysis

OBJECTIVE

To compare the efficacy of gentamicin and steroids in patients with Meniere's disease (MD).

METHODS

The study protocol was structured in accordance with the Population, Intervention, Comparison and Outcome (PICO) framework. We used "Endnote" (Thomson ResearchSoft; Stanford, Connecticut, the United States) to retrieve database documents. A systematic literature search of Web of Science and PubMed Database through May 2020 was conducted using specific search terms. Inclusion criteria, exclusion criteria, vertigo improvement, and exact hearing changes were defined. Review Manager 5.3 (Cochrane) was used for data analysis.

RESULTS

A total of 80 articles were searched from Web of Science and 23 articles were searched from PubMed database. After further reviewing the specific points of the inclusion criteria and exclusion criteria, 9 papers were finally selected. Intratympanic gentamicin (ITG) was superior to intratympanic steroid (ITS) in reducing the number of vertigo attacks (odds ratio (OR) 3.08, 95% confidence intervals (CI) [2.05-3.65]), probability (P) < 0.01). As for hearing improvement, we did the analysis twice. With all the studies included, the odds of hearing improvement (by "x") was 0.31 among patients receiving gentamicin compared to those treated by steroids (OR 0.31, 95% CI [0.16-0.61]). But after removing one study with outlying results from the analysis, this effect disappeared. Hearing loss of ITG and ITS was not statistically significant (P = 0.29).

CONCLUSIONS

ITG is superior to ITS in reducing the number of vertigo attacks in the treatment of MD (P < 0.01); the impact on hearing is more heterogeneous in the studies. Overall, there was no clear difference between ITG and ITS on hearing improvement and on hearing loss.