Postoperative normalization of prolonged ploom latency in the visual evoked magnetic field in a patient with occipital meningioma

A 49-year-old female with a left occipital parasagittal meningioma was found to have prolonged PlOOm latency of the pattern reversal visual evoked magnetic field only in the hemisphere containing the lesion. After total removal of the tumor, the PlOOm latency was normalized in the affected hemisphere. Based on current dipole models, all the PlOOm dipoles were localized at the lateral bottom of the calcarine fissures bilaterally, as indicated by our previous study with normal subjects. Since the tumor was located near the parietoocipital sulcus and distant from the primary visual cortex, disturbance of the higher visual cortex probably affected the PlOOm latency.