Safer optic nerve decompression surgery

Knowing about variations in the location of the optic nerve and ophthalmic artery can aid surgeons in performing optic nerve decompression - a delicate operation performed in patients with vision loss resulting from head injury, reports a study in the November Journal of Craniofacial Surgery.

Led by Dr. Jiping Li, a head and neck surgeon at Shanghai (China) Jiaotong University School of Medicine, the researchers performed a study in cadavers to analyze the anatomy of the optic nerve and ophthalmic artery. They present important information on useful anatomical landmarks and common variations for surgeons to be aware of when performing optic nerve decompression.

Optic nerve decompression, as first discussed in a pioneering 1976 study by the current Editors-in-Chief of LWW's Journal of Craniofacial Surgery and Annals of Plastic Surgery, is sometimes needed in patients who have loss of vision after head injury, such as from car crashes. Swelling from head trauma can place pressure on the optic nerve, causing a decreased vision or blindness. Urgent surgery is sometimes needed to relieve the pressure on the optic nerve, in the hope of restoring vision.

In their study, Dr. Li and colleagues performed simulated optic nerve decompression surgery in eight cadaver heads. The procedure is done using a minimally invasive approach using an endoscope—a telescope-like instrument that lets the surgeon see and operate within the skull. The surgery is done through a "transsphenoidal" approach, meaning through the sphenoid sinus—one of the air spaces behind the nose.

The study provided important information on key landmarks for surgeons to follow when navigating through the sinuses to reach the location of the optic nerve. The researchers also identified the most common sites of the optic nerve within the sinus and some common variations that may be found during the procedure. For example, one key landmark that is useful in guiding surgery was absent about 40 percent of the time.

A key goal of the study was identification of the ophthalmic artery, which closely follows the optic nerve—the surgeon must take meticulous care to avoid damaging the optic nerve. The researchers found that the ophthalmic artery starts below and a little to the side (inferomedial) compared to the optic nerve, but may intersect the nerve as it runs alongside.

Dr. Li and colleagues hope the new information on the anatomic relationships between the optic nerve, ophthalmic artery, and sphenoid sinus will help to guide surgeons in planning performing this precise endoscopic surgical procedure. They write, "Understanding these relationships facilitates identification of the optic nerve, avoids ophthalmic artery injury, and prevents resulting severe complications…the key [to] achieving good surgical outcomes."

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