Name: Surgical Induction of Endolymphatic Hydrops by Obliteration of the Endolymphatic Duct (Video) | JoVE Journal
Uploaded: 2010-01-22T16:52:00.000+00:00
Duration: 11 min 49 s
Description: Learn surgical blockade of the endolymphatic duct in guinea pigs to model endolymphatic hydrops for Meniere's disease research. This technique enables study of cochlear pathology and progressive hearing loss.

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5 minutes

This work was supported in part by a grant from the American Otological Society to CAM and by a grant from the University Hospitals Case Medical Center to KNA and CAM. We would like to thank Jeff Churney at Focus Medical Group, Inc. (Hinckley, OH) for providing us with a microscope camera. Video production services provided courtesy of Fusion Creative Marketing, Inc. (Valdosta, GA) We thank Jonathan Frankel and Alex Levitt at CWRU for their comments during the preparation of the video.

Part 1: Anesthesia and preparation for surgery
<ol>
 <li>An adult, female Duncan-Hartley guinea pig from Charles River International Laboratories, Inc. (Wilmington, MA) is anesthetized with ketamine 60 mg/kg and xylazine 12 mg/kg intramuscularly.</li>
 <li>Petroleum lubricant is applied to the eyes to protect the animal from corneal injury due to drying.</li>
 <li>The animal is shaved from the top of the head to the shoulders and between the ears.</li>
 <li>The shaved area is prepped in a sterile fashion first with 7.5% povidone-iodine followed by 70% ethyl alcohol.</li>
 <li>The animal is placed onto an operating table with warming blanket and onto a platform that elevates the head and flexes the neck. The head of the animal is directed away from the surgeon. Adequate flexion of the neck is required in order to adequately expose the occipital ridge.</li>
 <li>The animal is draped in a sterile fashion.</li>
</ol>
Part 2: Incision and exposure of the bony occiput
<ol>
 <li>Bupivacaine plus epinephrine (Marcaine) 0.25% is applied along the prospective incision site (midline dorsal skin incision along the occiput). This causes local vasoconstriction, limiting bleeding, and provides lasting post-operative analgesia after the animal wakes.</li>
 <li>Midline dorsal skin incision is made on the scalp along the occiput. <img src="/files/ftp_upload/1728/1728fig1.jpg" alt="Midline incision site diagram on rat for surgical procedure study and anatomical research." data-altupdatedat="1788235205000" data-alt="Figure 1"> Figure 1: Skin incision is made along the dorsal midline, as shown above.</li>
 <li>To gain adequate exposure, the skin is retracted laterally by placing a small curved hemostat on each side of the incision.</li>
 <li>A horizontal incision is made along the neck muscle to expose the bony occiput. At this stage the animal may twitch despite adequate anesthesia due to transection of the greater occipital nerve. Spinal cord transection is a danger with horizontal incision into the suboccipital region. This complication can be avoided by ensuring that underlying bone is always felt underneath the scalpel blade.</li>
 <li>With the suboccipital musculature incised to the bone, a third hemostat is used to retract the superior muscle edge. This hemostat is held in place by the surgical assistant.</li>
 <li>A Lempert periosteal elevator is used to expose the temporo-occipital suture.</li>
 </ol>
 Part 3: Drilling the temporo-occipital suture
 <ol>
 <li>Upon exposure of the temporo-occipital suture (Figure 2), an otologic drill with 1.5 mm diamond burr is used to drill inferio-laterally to the suture. </li>
 <li>Below the outer table of the skull, the spongy texture of the diploë (The intervening cancellous bone between tables of the skull) will become visible. Once the diploë has been drilled away, the inner table of the skull appears, along with a faint blue hue that is the sigmoid sinus.</li>
 <li>The margins of the sigmoid sinus are defined without penetrating the vessel. </li>
 <li>Once the bone overlying the sigmoid sinus has been sufficiently thinned, higher magnification is utilized and a straight pick is used to carefully remove the bone overlying the sigmoid sinus.</li>
 </ol>
 <img src="/files/ftp_upload/1728/1728fig2.jpg" alt="Temporo-occipital suture location, drilling area marked, bone anatomy study." data-altupdatedat="1788235205000" data-alt="Figure 2"> Figure 2 The area to be drilled partially overlies the temporo-occipital suture.
 Part 4: Obstruction of the Duct
 <ol>
 <li>The skeletonized sigmoid sinus is retracted medially to reveal the operculum. </li>
 <li>A 0.5 mm diamond burr is used to drill medial to the operculum and into the endolymphatic sac and duct. </li>
 <li>The endolymphatic duct is then packed with bone wax using a straight pick. </li>
 <li>The skull defect is then reinforced with Gelfoam (Pfizer, New York, NY). </li>
 <li>4-0 POLYSORB (United States Surgical, Norwalk, CT) suture is used to bring the muscle together. There is then a seamless transition to a subcutaneous suture technique for closing the skin incision. With this closure there is no need to remove sutures afterward and there is no risk that the animal will claw at the site and pull out a suture.</li>
 </ol>
 Part 5: Post-Operative Care
 The guinea pig is put in an incubator to maintain body temperature and checked at 30 minute intervals until awake and able to maintain a sternal position. The animal is inspected for respiration rate and body color. This center uses enrofloxacin (0.2 mL at 22.7 mg/mL, subcutaneously) and buprenorphine (0.05 mL at 0.3mg/mL, subcutaneously) for post-operative infection prophylaxis and pain control, respectively. Analgesic is given once on the day of surgery and twice on post-operative day one and two. Although antibiotics are not necessary for aseptic surgery, a five-day, twice a day course of prophylactic antibiotics may be givenonce on post-operative day three.
 Complications and Management
 <ol>
 <li>Respiratory depression The surgeon should always be aware of the animal s respirations. If breathing slows or stops, discontinue surgery and visually inspect for thoracic movement. If the animal is experiencing respiratory difficulty or labored breathing, check that the mouth and airway are not occluded. </li>
 <li>Sigmoid sinus penetration Use Gelfoam and compression along with the suction tip until bleeding is stopped.</li>
 <li>Dural penetration Cover the defect with Gelfoam.</li>
 <li>Vestibular damage Do not drill more than 1 mm lateral to the sigmoid sinus. Doing so risks injuring the posterior semicircular canal, which would invalidate all data for the guinea pig. </li>
 </ol>

<ol><li>Andrews, J. C., Bohmer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+surgical+approach+to+the+endolymphatic+sac+and+the+cochlear+aqueduct+in+the+guinea+pig%5BTitle%5D)+AND+%22Am+J+Otolaryngol%22%5BJournal%5D)">The surgical approach to the endolymphatic sac and the cochlear aqueduct in the guinea pig.</a> Am J Otolaryngol. 10, 61-66 (1989).</li>
<li>Kimura, R., Schuknecht, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Membranous+hydrops+in+the+inner+ear+of+the+guinea+pig+after+obliteration+of+the+endolymphatic+sac%5BTitle%5D)+AND+%22Pract+Otolaryngol%22%5BJournal%5D)">Membranous hydrops in the inner ear of the guinea pig after obliteration of the endolymphatic sac.</a> Pract Otolaryngol. , (1965).</li>
</ol>

Experiments on animals were performed in accordance with the guidelines and regulations set forth by the Institutional Animal Care and Use Committee at Case Western Reserve University.

In the weeks following surgical obstruction of the endolymphatic duct, the animal subject experiences fluctuating sensorineural hearing loss as measured by auditory evoked brainstem response. A sample of auditory brainstem response (ABR) recording is shown in Figure 3. The left ear serves as an unoperated control.
 <a href="http://www.jove.com/files/ftp_upload/1728/1728fig4.jpg"><img border="0" src="/files/ftp_upload/1728/1728fig3tmb.jpg" alt="Auditory signal analysis, waveforms comparison chart of control and operat...

surgical induction of endolymphatic hydrops by obliteration of the endolymphatic duct

Surgical Induction of Endolymphatic Hydrops by Obliteration of the Endolymphatic Duct

Surgical induction of endolymphatic hydrops (ELH) in the guinea pig by obliteration and obstruction of the endolymphatic duct is a well-accepted animal model of the condition and an important correlate for human Meniere's disease. In 1965, Robert Kimura and Harold Schuknecht first described an intradural approach for obstruction of the endolymphatic duct (Kimura 1965). Although effective, this technique, which requires penetration of the brain's protective covering, incurred an undesirable level of morbidity and mortality in the animal subjects. Consequently, Andrews and Bohmer developed an extradural approach, which predictably produces fewer of the complications associated with central nervous system (CNS) penetration.(Andrews and Bohmer 1989) 
The extradural approach described here first requires a midline incision in the region of the occiput to expose the underlying muscular layer. We operate only on the right side. After appropriate retraction of the overlying tissue, a horizontal incision is made into the musculature of the right occiput to expose the right temporo-occipital suture line. The bone immediately inferio-lateral the suture line (Fig 1) is then drilled with an otologic drill until the sigmoid sinus becomes visible. Medial retraction of the sigmoid sinus reveals the operculum of the endolymphatic duct, which houses the endolymphatic sac. Drilling medial to the operculum into the area of the endolymphatic sac reveals the endolymphatic duct, which is then packed with bone wax to produce obstruction and ultimately ELH. 
In the following weeks, the animal will demonstrate the progressive, fluctuating hearing loss and histologic evidence of ELH.

This video shows how to surgically obstruct the guinea pig's endolymphatic duct to produce endolymphatic hydrops.

Surgical induction of endolymphatic hydrops (ELH) in the guinea pig by obliteration and obstruction of the endolymphatic duct is a well-accepted animal ...

Hi, my name is Chris Edden. I'm a researcher at Case Western Reserve University in the Department of Otolaryngology head and neck Surgery. Today I'll be describing the surgical blockade of the endo lymphatic duct in the Guinea pig, which produces endo, lymphatic hydros and is used to model many errors, disease related ear pathology.Ando.Lymphatic hydros is a swelling of the endo, lymphatic compartment of the cochlea and is a key histological marker for knee's disease. Here you see a cross-sectional picture of a normal cochlea with two peri lymphatic compartments, the scale of phony and scale of hasibe, and a non dilated scale of media, which is continuous with the endo lymphatic duct, the structure we're operating on within weeks of the surgical procedure, the scale edia becomes dilated as indicated here, and reisner's membrane becomes distended. The animals also undergo progressive fluctuating hearing loss on the surgical ear.Just as in many air's disease, surgical induction of hydros in the Guinea pig has been the gold standard animal model for human Meniere's disease since it was first described in 1965 by Robert Kor and Harold Schneck. Although the procedure was initially performed using a more invasive intradural approach, our center prefers an extradural approach because it results results in less morbidity and mortality for the animal. The following is a description of the materials, animal care and surgical approach necessary for successful and humane performance of this rather intricate procedure.First, I'll describe the surgical materials needed. The animal is an adult female, Duncan Hartley, albino Guinea pig from Charles River International Laboratories Incorporated. For room preparation and sterile setup, you'll need sterile surgical attire, an operative microscope with sterile cover and Mars, small fenestrated drape, intraoperative warming pad suction apparatus.A number five, suction, a number 40 suction sterile saline, stainless steel basin, and a head holder. For anesthesia, you'll need ketamine 60 milligrams per kilogram and xylazine 12 milligrams per kilogram Preoperatively. You'll need a petroleum based I lubricant an electric shaver, Betadine, and 70%ethyl alcohol intraoperatively, you'll need 0.6 milliliters of 0.25%marking a number 11 disposable safety scalp, three curved hemostats, a lier periosteal elevator, WEX cell surgical spears and otologic drill, A 1.5 millimeter diamond burr and a 0.5 millimeter diamond burr.A straight pick a bone curette, a 10 cc syringe bone wax gel foam four oh absorbable suture with a P 13 cutter needle, addin forceps, diamond jaw needle driver, and suture scissors. For post-op care, you'll need a clean cage with warming pad. Point two mls of inter floxacin at 22.7 milligrams per milliliter.Point zero five milliliters of buprenorphine 0.3 milligrams Per milliliter. First anesthetize the Guinea pig With ketamine 60 milligrams per kilogram and xylazine 12 milligrams per kilogram intramuscularly. This regimen allows for 60 to 90 minutes of anesthesia without respiratory depression, which is usually plenty of time for the performance of this procedure.After anesthetizing the animal, a petroleum-based lubricant is applied to the eyes. Next, the back of the head is shaved with electric clippers from the upper thoracics to the top of the head. Then the site is prepped with Betadine, followed by alcohol.Now the animal is ready for surgery. My name is Dr.Cliff McGillion. I am a professor of Otolaryngology Head and neck Surgery here at Case Western Reserve University Hospitals in Cleveland and the director of Otology and Neurotology.What I want to talk to you today about is the surgical technique for inducing endo lymphatic hydros in the Guinea pig. We go extraorally and expose the sigmoid sinus and just anterior to the sigmoid sinus and lateral to the sigmoid sinus. We find the O perm of the endo lymphatic system and remove the duct material and the sac material and actually drill out the duct under direct visualization.The most important part I think of the procedure is skeletonizing the sigmoid sinus and then medial that and directly visualizing the O curriculum of the endo lymphatic duct. Once the surgical site is prepared, the animal is transferred to the OR and placed onto a head holder. The neck is flexed to give adequate exposure of the occipital ridge and draped in a sterile fashion for the health and safety of the animal.Observe the same sterile technique that will be required for a human patient in order to maintain adequate body temperature during the procedure, be sure that a warming pad is placed under the operative surface before first incision. Marking is injected around the surgical site. The surgical procedure is begun by making a midline dorsal skin incision on the scalp Along the occiput to gain Adequate exposure, retract the skin by placing a hemostat on each side of the incision, electrocautery will not be necessary as the Guinea pig has a robust hemostatic mechanism.Next, a horizontal incision is made along the neck muscle. To expose the bony occiput, A well-placed incision may immediately expose the temporal occipital suture line as shown here. Transection of the greater occipital nerve that commonly underlies the muscle may make the animal twitch.Despite adequate anesthesia when cutting through the muscle, it is important to feel the bone underneath the blade. If not, the incision may be too low, which could risk spinal cord transection once through the neck muscle. A third hemostat is used to grasp the superior portion of the incision and is held in place by the surgical assistant.Blunt dissection is used to expose the occipital bone. Remember to stay on the right side of the external occipital crest at all times and that the left ear serves as a control. In this model, A lumper periosteal elevator is then used to further expose the cranium and expose the external occipital crest and temporal occipital suture line Drilling with a 1.5 millimeter diamond burb begins just inferior to the suture line.The goal is to expose the posterior foss auraura and the sigmoid sinus. All drilling must stay on or inferior to the temporal occipital seizure line At all times. Keep a number five suction tube to suction the blood.Also have an assistant keep the field irrigated with sterile saline. Continuously dripping from a 10 cc syringe. Drilling will cause some bleeding from the marrow, but the diamond bur can be used to stop the bleeders at a depth of approximately one millimeter.A faint blue line will become visible. This is the sigmoid sinus. Just stand here.Your un lateral to the sigmoid sinus. The a perm of the endo lymphatic duct can be found. It is important to define the edges of the sigmoid sinus without penetrating it.Once the overlying bone has been sufficiently thin, drilling is then stopped and suction is changed to a number 40. Higher magnification is also utilized. A straight pick is used to gently remove the overlying bone.Sigmoid sinus is gently retracted, medially revealing the operculum, which may not be overtly visible as it will be often be obscured by blood. Now the skeletonized sigmoid sinus is gently retracted, medially revealing the operculom. The groove is now drilled with a smaller 0.5 cutting bit obliterating the endo lymphatic sac, and ultimately leading to the Endo lymphatic duct.The duct is visible as a dark oval within the whiteness of the surrounding bone. About one Millimeter of the duct is drilled before it is packed with bone wax. Bone wax is pushed into the duct using gel foam.This occlusion of the endo lymphatic duct will induce endo Lymphatic hydro drops 4.0 poly shorb suture is used to bring the muscle together. Then there's a seamless transition to a subcutaneous suture technique for the skin incision. With this closure, there is no need to remove sutures afterward, and there is no risk that the animal will claw the site or pull a suture or staple out.Postoperatively, the Guinea pig is put into an incubator to maintain body temperature with 30 minute checks until they're awake. The animal is inspected for respiration rate and body color. This center uses the broad spectrum antibiotic inin and buprenorphine for pain complications.As with any surgery, there are risks to the subject. So now I'll go over some possible intraoperative complications and how to avoid them. Respiratory depression, the surgeon should always be aware of the animal's respirations if breathing stops or slows.Discontinue surgery and visually inspect for thoracic movement. If the animal's apneic, check that the mouth and airway are not occluded. Sigmoid sinus penetration use gel foam and compression along with the suction tip until bleeding is stopped.Dural penetration cover with gel foam vestibular damage do not drill more than one millimeter lateral to the sigmoid sinus or else the posterior semicircular canal can be injured, which would invalidate all data for that particular Guinea pig. Surgical blockage of the endo lymphatic duct in the Guinea pig is a technically demanding surgery, but with proper tools, instruction, and knowledge of the relevant anatomy, it can be performed in a way that is both humane to the animal and useful as a model for human Meniere's disease.

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Learn surgical blockade of the endolymphatic duct in guinea pigs to model endolymphatic hydrops for Meniere's disease research. This technique enables study of cochlear pathology and progressive hearing loss.

Surgical Induction of Endolymphatic Hydrops by Obliteration of the Endolymphatic Duct

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