Fluctuating hemiparesis caused by a quadrigeminal arachnoid cyst: case report.

A 42-year-old woman presented with intermittent hemiparesis mimicking a reversible ischemic neurologic deficit. Magnetic resonance imaging (MRI) demonstrated a compression of the left side of the midbrain by a quadrigeminal arachnoid cyst without hydrocephalus. After the cystic wall was widely excised under operating microscope, the patient made a good recovery and remained well at a follow-up of 18 months. The absence of hydrocephalus in a symptomatic patient with a quadrigeminal cyst was exceptional, which might result from the early diagnosis with MRI. The use of microsurgical technique made it possible to excise the cystic wall widely and omit a shunting procedure.