The value of VEP in the diagnosis and post-operative monitoring of meningioma.

Meningiomas are the most frequently reported primary intracranial neoplasms. At first they usually cause unilateral visual loss but eventually result in a bilateral loss of vision. Depending upon the size and location of the tumour, the ocular signs and symptoms of meningiomas may include visual field abnormalities, optic atrophy, papilledema, diplopia and proptosis. This case report highlights the value of visual evoked potentials (VEP) in a patient with unexplained bilateral optic atrophy and a progressive loss of vision over 2 years. As a result of a delayed response in the VEP recorded from the right eye, a compressive lesion of the optic nerve was suspected. That prompted the referring ophthalmologist to request a MRI scan which led to the diagnosis of meningioma. Following the subtotal removal of the suprasellar meningioma, the remaining vision in the right eye improved and the latency of the VEP returned to the normal range. However, the VEP from the blind eye (left) did not show any measurable response either pre- or postoperatively. Experience with this patient suggests that early recognition of optic nerve compression is vital to an optimal outcome and the VEP technique, which is much more cost-effective than MRI, is clinically useful for detecting such compressive lesions.