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Thread: Endolymphatic Shunt Operation pictures - Ear Atlas

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    Default Endolymphatic Shunt Operation pictures - Ear Atlas

    Indications
    Endolymphatic sac shunting is indicated for the control of the disabling vertigo of Meniere disease that has failed to improve with medical therapy. The side of involvement in unilateral Meniere disease should be clearly evident based on audiography and auditory symptoms, such as tinnitus and aural fullness. The patient should meet the most current criteria for the diagnosis of Meniere “definite” disease. If bilateral Meniere disease is present, endolymphatic sac surgery is performed on the worse offending symptomatic side.

    Medical management of Meniere disease includes a low-salt diet and diuretics. Other adjunctive medical options include vasodilators, systemic or intratympanic corticosteroids, and allergy or immune-mediated treatment. Vestibular suppressants and sedatives are used for symptomatic control of vertigo. If these are not sufficient to control the episodic, disabling vertigo, either nonablative or ablative therapies may be considered.

    Ablative treatment involves destruction of the neuroepithelium or sensory structures of the inner ear (deafferentation). Therefore, permanent hearing loss and vestibular dysfunction can be expected after such therapy. Ablative procedures include intratympanic gentamicin (chemical labyrinthectomy), surgical labyrinthectomy, and vestibular nerve section. The only nonablative treatment is endolymphatic sac surgery.

    Contraindications
    Patients who do not fulfill the diagnostic criteria of “definite” Meniere disease should not be considered for endolymphatic sac shunt surgery. Patients with vertigo due to nonvestibular causes or central nervous system abnormalities should not undergo endolymphatic sac surgery.

    Patients with definite Meniere disease whose condition is well-controlled with medical therapy should not undergo endolymphatic sac shunt surgery. These include patients with infrequent vertiginous attacks who can still carry on daily life activities, relatively uninterrupted by the dizziness. Patients who are chronically imbalanced and affected with disequilibrium should not undergo endolymphatic sac surgery, as these symptoms result from to end-organ vestibular damage due to long-term Meniere disease.

    Endolymphatic sac surgery is not used to reverse longstanding hearing loss, to eliminate aural fullness, or to alleviate the tinnitus of Meniere disease.
    Endolymphatic Shunt Operation pictures Atlas attachment.php?s=5d0c18bb080f304186f6d140e5ad12ff&attachmentid=1846&d=1441386168

    Technical Considerations
    Surgical access to the endolymphatic sac is via a postauricular transmastoid extradural approach. Standard mastoidectomy procedures are followed with the additional steps of skeletonization of the sigmoid sinus extending inferiorly toward the jugular bulb, sinodural angle, and the posterior fossa dura that lies between the sigmoid sinus and posterior semicircular canal. The endolymphatic sac is extradurally located on the posterior fossa dura in the infralabyrinthine region as a dural duplication or thickening.
    The decision by the surgeon to proceed with either endolymphatic sac decompression or endolymphatic sac shunt placement to the mastoid depends on surgeon preference, experience, and clinical outcomes.

    Potential structures at risk for injury include posterior semicircular canal leading to fenestration and labyrinthine injury, posterior fossa dura leading to cerebrospinal fluid (CSF) leak, facial nerve leading to paralysis, and sigmoid sinus leading to hemorrhage.

    Outcomes
    Studies have demonstrated endolymphatic sac shunting to be effective in control of the vertigo in Meniere disease in 50%-75% of patients. In fact, it appears that endolymphatic sac decompression is as effective as endolymphatic sac shunting for control of vertigo.

    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.

    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.

    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.
    Endolymphatic Shunt Operation pictures Atlas attachment.php?s=5d0c18bb080f304186f6d140e5ad12ff&attachmentid=1847&d=1441386279

    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

    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.

    References:
    http://emedicine.medscape.com/articl...riprocedure#b7











    Last edited by Medical Photos; 09-04-2015 at 05:04 PM.

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