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Services & Procedures

Optic Nerve Sheath Decompression

Patients with severe pseudotumor cerebri sometimes require optic nerve sheath decompression (ONSD). This procedure is also known as optic nerve sheath fenestration. This is a procedure designed to save vision. Secondarily it can reduce the severity of headaches in some patients. The typical candidate for ONSD has either:

  1. Failed medications
  2. Has a problem with the adverse effects of a medication
  3. Has severe visual loss
  4. Threatened visual loss from extremely elevated intracranial pressure

ONSD can be thought of as a lumbar puncture behind the eye … except you are asleep and do not feel anything! Dr. McHenry has performed more ONSDs than anyone in the Southwest and has the largest population of patients with pseudotumor cerebri. In his hands the operation takes approximately 20 minutes. You will spend more time in the pre op area than it will take him to do the surgery.

After Dr. McHenry and his anesthesiologist have spoken with you in pre-op, you will be given some sedation and then brought to the operating room. In the modern world of anesthesia, many patients do not require the older breathing tubes called endotracheal tubes but can undergo surgery with the less invasive LMA tube. This helps in post-op recovery.

The surgery is performed under the operating microscope. The eye is pulled to one side and a series of microscopic holes, or fenestrations are cut into the sheath. Then the arachnoid trabeculations, which often trap fluid, are lysed with a micropick. This is the key to successful surgery. Patients loose vision because of pressure and subsequent poor blood flow at the area in the optic nerve where the fibers turn to enter the eye. By relieving the pressure, blood flow is restored and vision is preserved. The pressure goes down to zero where the holes are made. Overtime, scarring occurs and protects the nerve from the effects of pressure.

You will wake up in the recovery room with a patch on your eye. We will remove the patch in the morning. You may have some short term double vision in the immediate post-operative period until the eyes get used to working together again. We only do one eye at a time because your vision will temporarily be quite blurry. We will then get you set up to schedule surgery on the opposite side.

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