Optic nerve sheath advances detailed

Chicago-A number of advances have been made in the ability to diagnose and manage optic nerve sheath meningiomas. Neil R. Miller, MD, described how best to handle these tumors during the William F. Hoyt Lecture at the American Academy of Ophthalmology annual meeting.

"There have been some major shifts in the paradigms for diagnosing and managing of these lesions, particularly during the past few years," said Dr. Miller, professor of ophthalmology, neurology, and neurosurgery, and the Frank B. Walsh Professor of Neuro-Ophthalmology at The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore.

Imaging patterns

"There are three patterns of imaging observed with optic nerve sheath meningioma. The most common one is the diffuse process along almost the entire length of the optic nerve. Calcifications may be seen on computed tomography, and there may be a tram track sign related to the tumor that is surrounding the optic nerve," Dr. Miller said. "A second pattern is that of a fusiform mass surrounding a normal or atrophic optic nerve. In such cases, the tumor can be easily identified on MRI as a low-density structure passing through the center of the enhancing fusiform mass.

A very interesting aspect in the diagnosis of optic nerve sheath meningioma was identified recently, according to Dr. Miller, namely, the irregularity of the outside aspect of the optic nerve sheath meningioma. He demonstrated the small coronal extensions of the tumor that are virtually pathognomonic of this pathology.

"It is extremely important that surgeons observe the tumor encircling the optic nerve and look for these extension wisps," he advised.

Management

Observation of these patients is an accepted form of management in certain circumstances, such as in patients with no substantial visual dysfunction, loss of vision, or cranial extension of the tumor.