Effects of methylprednisolone on cortical neural activity, blood flow, and water content in air exposure-induced cerebral edema.

The correlation of changes in cortical neuron activity with water content and local cerebral blood flow was investigated in cats with brain edema produced by air exposure. The further effect of high-dose methylprednisolone on these factors was studied. Six hours after exposure of the brain surface to air, the water content of the white matter significantly increased. The local blood flow of the cortex and white matter significantly decreased with significant suppression of cortical neural activity (direct cortical response), indicating that ischemia was responsible for neural suppression. A single, large dose of methylprednisolone (30 mg/kg, i.v.) at the beginning of air exposure significantly reduced brain edema of the cortex and white matter 12 h after air exposure and improved the local blood flow of the cortex. Methylprednisolone also caused a remarkable improvement in cortical neural activity. This steroid effect on cortical neural function may play a role in the rapid neurologic improvement observed with their use in addition to the effect on brain edema.