This article demonstrates an extradural approach to obliterate the guinea pig endolymphatic sac and injure the endolymphatic duct with a fine pick in order to induce experimental endolymphatic hydrops.
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Method Article
A Revised Surgical Approach to Induce Endolymphatic Hydrops in the Guinea Pig
In This Article
Summary
Abstract
Endolymphatic hydrops is an enlargement of scala media that is most often associated with Meniere's disease, though the pathophysiologic mechanism(s) remain unclear. In order to adequately study the attributes of endolymphatic hydrops, such as the origins of low-frequency hearing loss, a reliable model is needed. The guinea pig is a good model because it hears in the low-frequency regions that are putatively affected by endolymphatic hydrops. Previous research has demonstrated that endolymphatic hydrops can be induced surgically via intradural or extradural approaches that involve drilling on the endolymphatic duct and sac. However, whether it was possible to create an endolymphatic hydrops model using an extradural approach that avoided dangerous drilling on the endolymphatic duct and sac was unknown. The objective of this study was to demonstrate a revised extradural approach to induce experimental endolymphatic hydrops at 30 days post-operatively by obliterating the endolymphatic sac and injuring the endolymphatic duct with a fine pick. The sample size consisted of seven guinea pigs. Functional measurements of hearing were made and temporal bones were subsequently harvested for histologic analysis. The approach had a success rate of 86% in achieving endolymphatic hydrops. The risk of cerebrospinal fluid leak was minimal. No perioperative deaths or injuries to the posterior semicircular canal occurred in the sample. The presented method demonstrates a safe and reliable way to induce endolymphatic hydrops at a relatively quick time point of 30 days. The clinical implications are that the presented method provides a reliable model to further explore the origins of low-frequency hearing loss that can be associated endolymphatic hydrops.
Introduction
Endolymphatic hydrops is an enlargement of scala media. The presence of endolymphatic hydrops can be measured using the cross-sectional area of scala media. It is thought that clinical endolymphatic hydrops can be associated with low-frequency sensorineural hearing loss, such as that seen in Meniere's disease. But the origin(s) of the hearing loss remain unclear. To adequately study the origins of low-frequency hearing loss associated with endolymphatic hydrops, a reliable model is needed.
In 1965, Kimura and Schuknecht described how to induce endolymphatic hydrops in the guinea pig using an intradural approach1
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Protocol
All procedures listed immediately below in the Protocol section were conducted as described in protocols approved by the Washington University in St. Louis Institutional Animal Care and Use Committee.
1. Anesthetic Induction and Monitoring of Vital Signs
NOTE: This study used pigmented NIH-strain guinea pigs obtained from an in-house breeding colony.
- Use guinea pigs of either sex, weighing at least 350 g.
- Place the guinea pig in a neonatal warming isolette and give a ketamine/xylazine mixture intraperitoneally (50 mg/kg ketamine and 10 mg/kg xylazine) for induction anesthesi....
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Results
The presented method used an extradural approach to obliterate the endolymphatic sac and injure the endolymphatic duct with a fine pick in seven guinea pigs consisting of two males and five females. The average duration of surgery was 2 hours from incision to closure. The total drill time ranged from 5-10 minutes. Up to 4 hours was needed for the guinea pig to fully emerge from anesthesia. There were no intra-operative or post-operative deaths in the sample. There were no injuries to the .......
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Discussion
The presented extradural method had a success rate of 86% in achieving histologically confirmed endolymphatic hydrops and low-frequency hearing loss. The method reliably achieved histological evidence of endolymphatic hydrops by post-operative day 30, consistent with prior studies that used an intradural approach2. The significance of the method with respect to existing methods is that a CSF leak is not required, thus removing a potential confounding variable that has been suggested to result in a.......
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Disclosures
The authors have nothing to disclose.
Acknowledgements
We thank Shannon M. Lefler for assistance with figures and the Table of Materials. Research reported in this publication was supported by the National Institute of Deafness and Other Communication Disorders within the National Institutes of Health, through the "Development of Clinician/Researchers in Academic ENT" training grant, award number T32DC000022 (C.V.V.) and by R01 DC014997 (J.T.L). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
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Materials
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| 12 mL syringe | Henke-Sass Wolf | 5100-X00V0 | |
| 1 mL and 3 mL syringe | BD Precision(Ordered from Fischer Sci) | 14-826-87 15859152 | |
| 27.5 butterfly gauge needle | Terumo Surflo Winged Infusion Set, Terumo Corporation, Japan) (Ordered from McKesson) | 448407 | |
| 4-0 suture | McKesson | 1034507 | |
| 4 x 4 gauze sponges | Dukal (Ordered form McKesson) | 374454 | |
| 60 mL syringe | Fisher Sci | 22-031-375 | |
| Anspach otologic drill | Anspach | SC2100 | |
| atipamezole | Zoetis | 107204-6 | |
| autoclave | Fisher sci | 15-103-0508 | |
| autoclave bags | McKesson | 524881 | |
| bayonet separator | Olympus | AL 130564 | |
| bupivicaine | auro Medics Pharma | 555150-169-10 | |
| clear sterile drape | 3M | 1020 | |
| cotton balls | Fisherbrand (ordered from Fisher Sci) | 22-456-885 | |
| cotton swabs | McKesson | 508716 | |
| diamond burrs #3, #2, #1, and #0.5 mm | Anspach | QD8-3SD; QD8-2SD; QD8-1SD; QD8-05SD | |
| diaper pad | McKesson | 945330 | |
| disposable 15 blade | Swann-Morton | 0305 | |
| enrofloxacin | Hospira | 0409-4888-01 | |
| epinephrine | McKesson | 63739-0456 | |
| eye ointment | Dechra Vet Products | 17033-211-38 | |
| Freer elevator | Grace Medical | 215100FX | |
| gelfoam | Pfizer (Ordered from McKesson) | 82830 | |
| hair trimmers | Oster Power Pro Cordless (ordered from Amazon) | 078400-020-000 | |
| iodine scrub | Purdue Pharma (ordered from mcKesson) | 521243 | |
| iris scissors | Olympus | CL-542114 | |
| ketamine | Henry Schein Animal Health | 55853 | |
| lactated ringers | B. Braun Medical (ordered from McKesson) | 186662 | |
| lancet knife by Rosen | Grace Medical | 151100FX | referred to as curette in the text |
| lubricant | Milex (ordered from Cooper Surgical) | MX5030 | |
| masking tape | 3M (ordered from fisher sci | 19047259 | |
| metal rectangle basin | Amazon | B07NQDBC6T | |
| needle holder | Olympus | CR 213015-ENT | |
| needles: 27 gage, 18 gauge | BD Precision(Ordered from Fischer Sci) | 14-826-48 14-826-5D | |
| neonatal warming isollete | Air Borne Life Support Systems | 731-1800 | |
| operating microscope | Carl Zeiss | OPMI pico | |
| oxygen tank | AirGas | OX USP200 | |
| pulse ox | CapnoTrue (Ordered from Medacx) | M-3090112001 | |
| rectal probe with heating blanket | Harvard Apparatus | probe: PY2 50-7217 Heating Blanket: PY2 50-7214 | |
| red body holder | Lichtenhan Lab | N/A | In-house product |
| right angle | Olympus | BV-230337 | |
| rosen needle | Olympus | AM-130566 | customized, it is the instrument I use to tear the sac |
| rubber tubing for O2 administration | Fisher Sci | 14-171-104 | |
| saran wrap | Fisher Sci | NC9617977 | |
| stereotactic head holder | WUSTL Instrument Machine Shop | N/A | In-house product |
| sterile drapes | Cardinal Health | 7553 | |
| suction tube by Baron | Grace Medical | 034903FX 034905FX | #3 and #5 Suction |
| tissue forceps adson brown | Grace Medical | 325112FX | |
| Weitlander retractor | Olympus Grace Medical | BL200011 100313FX | |
| xylazine | Akorn | 59399-110-20 |
References
- Kimura, R. S., Schuknecht, H. F. Membranous Hydrops in the Inner Ear of the Guinea Pig after Obliteration of the Endolymphatic Sac. Pract oto-rhino-laryng. 27, 343-354 (1965).
- Salt, A. N., DeMott, J.
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