Optic Nerve Sheath Decompression

Abstract

Optic nerve sheath decompression (ONSD) or fenestration refers to a surgical technique that creates a window through the dural and arachnoid meningeal layers of the retrobulbar optic nerve sheath to release pressure on the optic nerve. ONSD for treatment of visual loss secondary to refractory papilledema was first described by DeWecker in 1872. Later that century, Carter and Müller published the second case series of optic nerve sheath fenestrations. However, despite these and several additional reports, the clinical benefit of performing this procedure was still questioned. In addition, alternative cerebrospinal shunting procedures were developed for patients with increased intracranial pressure. Renewed interest arose in 1964 when Hayreh demonstrated the effectiveness of ONSD in relieving experimental papilledema in rhesus monkeys. Various supporting clinical publications have since followed, starting with Smith, Hoyt, and Newton’s description in 1969 of relief of chronic papilledema by ONSD. Surgical intervention is considered for patients with progressive visual loss secondary to elevated intracranial pressure (ICP) in whom conservative management, such as medications (acetazolamide and furosemide) and weight control, has failed. Occasionally surgery is used primarily in patients whose visual function has already reached a critical level. Examples include patients in whom vision has declined to a disabling level in hopes that rapid papilledema resolution will result in some visual return. Surgery is also considered primarily in those with little remaining vision, in whom any further visual loss would carry substantial functional impact should conservative management fail. Once surgical intervention is deemed necessary, ONSD is one of several options. Cerebrospinal fluid (CSF) shunting in the form of ventricular–peritoneal (VP) or lumbar–peritoneal (LP) shunting can be considered. A deciding factor for some is the presence of headache, which is more effectively managed with VP or LP shunting. Comparative trials of ONSD and other CSF shunting procedures are lacking. Consequently, some medical centers opt for ONSD as the first-line surgical option, while others recommend alternative shunting procedures. At present, the only uniformly accepted therapeutic indication for ONSD is management of visual loss related to elevated ICP. The most common setting for ONSD is idiopathic intracranial hypertension.