Endolymphatic Shunt Placement Periprocedural Care

Updated: Mar 16, 2015
  • Author: Matthew Ng, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
  • Print
Periprocedural Care

Patient Education & Consent

When endolymphatic sac surgery is indicated, the surgeon should explain to the patient, in the simplest terms, that the purpose of the surgery is to access that part of the inner ear putatively responsible for drainage or absorption of endolymph. By removing the surrounding bone, external pressure is relieved from the endolymphatic sac and duct. By creating an opening into the sac and placing a silicone shunt, a portal will be created for continuing drainage of endolymph into the mastoid cavity.

Potential risks and complications include bleeding, infection, CSF leak, dizziness, hearing loss (total or partial), facial paralysis, and failure to achieve improvement in the disabling vertigo. Risk of hearing loss has been estimated to be 1%-2% of endolymphatic sac cases.

Options and alternatives should be discussed in the preoperative counseling period. Usually, if a patient with Meniere disease has decided to consider endolymphatic sac surgery, the only other treatment options include ablative-type interventions to control the disabling vertigo. These include intratympanic gentamicin, surgical labyrinthectomy, and vestibular nerve section.

Postoperative instructions are given to the patient prior to surgery. This will assist patients in their preparation for surgery. Typically, after uneventful surgery, the patient can be discharged the same day of surgery. The patient may be kept overnight in the hospital for observation if any complications are encountered during the surgery, such as CSF leak or sigmoid sinus injury. Mastoid pressure dressings are kept on for 24 hours. Local wound care is administered as appropriate.

Next:

Pre-Procedure Planning

Prior to surgery, audiogram is obtained to document the hearing status. The audiogram can be used to assess hearing changes as a result of the surgery and as a baseline to monitor future hearing changes as the disease progresses.

In cases of unilateral Meniere disease, ENG with caloric testing is performed to determine if contralateral vestibular hypofunction is present. If this is the case, the presence of contralateral subclinical endolymphatic hydrops is a distinct possibility. Clinical suspicion of bilateral Meniere disease may arise if there is aural fullness, tinnitus, or an incipient low-tone sensorineural hearing loss in the contralateral ear. If bilateral Meniere disease is present, ablative procedures are avoided to prevent bilateral vestibular hypofunction and chronic imbalance, disequilibrium and oscillopsia.

Temporal bone CT scan should be obtained prior to surgery to determine whether the sigmoid sinus is anteriorly situated, which will require more aggressive skeletonization of the sigmoid sinus with decompression and posterior retraction to gain access to the endolymphatic sac. Mastoid pneumatization is assessed to determine the ease of exenterating the air cells just before reaching critical structures. Jugular bulb position is checked to make sure that it is not high-riding so that inadvertent injury will be avoided as bone removal over the sigmoid sinus is undertaken adjacent to the mastoid tip area. The vestibular aqueduct is assessed to make sure that it is not hypoplastic. This would make identification of the endolymphatic sac more difficult. The position of posterior semicircular canal relative to the endolymphatic sac is assessed so that inadvertent fenestration of the canal will be avoided.

Previous
Next:

Equipment

Surgical instrumentation required for endolymphatic sac surgery is the same as that used for chronic ear and lateral skull base surgery (high speed otologic drill, operating microscope and facial nerve monitor). Facial nerve monitoring would be helpful particularly when bone removal and dissection are undertaken adjacent to the retrofacial air cells. The most vulnerable area of the facial nerve at risk is the mastoid segment of the facial nerve.

Previous
Next:

Patient Preparation

General anesthesia is administered during endolymphatic sac surgery. The use of muscle paralytics is avoided during anticipated periods of facial nerve monitoring and stimulation.

Patient positioning during endolymphatic sac surgery is the same as for other transmastoid neurotologic surgeries. After induction of general anesthesia, the operating table is turned 180 degrees. The anesthesiologist is situated at the foot of the bed. The surgeon is at the head of the bed. A pillow is placed under the knees to prevent strain on the patient’s lower back lying supine. Patient is strapped across the upper torso and hips to avoid patient movement during table rotation. The patient’s head is turned opposite the operation side. There is no need for head fixation with pinions.

Anesthesia

Local anesthetic with vasoconstrictor (eg, 1% lidocaine with 1:100,000 epinephrine) is used.

Previous
Next:

Monitoring & Follow-up

Postoperative monitoring largely depends on whether any complications were encountered during surgery. If a dural or sigmoid sinus tear was encountered, the patient should be monitored closely for acute neurologic changes or an expanding wound hematoma. Postoperative vertigo should be assessed with examination looking for irritative nystagmus that might indicate injury to the posterior semicircular canal.

Postoperative audiography is obtained 2 months after surgery to document hearing. At this time, the patient will also be able to discern whether the operation has been effective and has reduced the frequency of vertiginous attacks.

Previous