Lateral approach for an optic nerve sheath fenestration
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This is Richard Allen at the University of Iowa.
This video demonstrates an optic nerve sheath fenestration using a lateral approach.
A 15 blade is used to make a lateral canthotomy. The monopolar cautery is then used to perform an inferior cantholysis followed by a superior cantholysis. A 4-0 Silk suture is then placed through the lateral upper and lower lid margins to provide traction during the case. The lateral orbital rim is exposed with the monopolar cautery. A 4-0 Silk traction suture is then placed beneath the lateral rectus muscle and the eye is placed in an adducted position.
Dissection is then carried out with Westcott scissors in the area between the lateral rectus muscle and lacrimal gland. Blunt dissection is then performed with small malleable retractors between the lateral rectus muscle and lacrimal gland. This is performed in order to expose the intraconal orbital fat. The septa of the orbit often have to be transected with the Westcott scissors. This allows exposure of the intraconal compartment where the optic nerve can be palpated with the malleable retractors. Additional blunt dissection can be performed with long cotton tipped applicators. This can then be followed by dissection through additional septa with the Westcott scissors. Once the optic nerve is identified, moist neurosurgical cottonoids can be used to pack the fat away from the optic nerve.
The surgeon can then switch to the operating microscope. The approach in this view is from the lateral position. The optic nerve is identified with the malleable retractors. The area is zoomed in. Myringotomy forceps are used to grasp the sheath of the optic nerve. The Yasargil neurosurgical scissors are then used to incise the optic nerve sheath. This is done until a gush of fluid is appreciated. The Yasargil scissors are then used to complete a window in the optic nerve sheath. Some surgeons like cut just slits; I prefer to cut an entire window in the nerve sheath. This is performed with both the straight and curved Yasargil scissors. After the window is completed, the sheath can be sent to the pathologist for evaluation. The window is demonstrated. The malleable retractors are removed.
The lateral cantholysis is then repaired by engaging the periosteum of the lateral orbital rim with a 4-0 Vicryl suture. This is followed by engaging the lower lid margin followed by the upper lid margin, and then to the periosteum of the lateral orbital rim. The suture is tied which results in attachment of the lateral upper and lower lid to the lateral orbital rim. The canthotomy is then repaired with interrupted 5-0 fast absorbing sutures. At the conclusion of the case, antibiotic ointment is placed over the repair three times a day and the patient returns in one week for reevaluation.