Abnormal vasomotor response of human epileptogenic cortex to reversal of hyperventilation a long-term surface cerebral blood flow monitoring study

Human epileptogenic and nonepileptogenic surface cerebral blood flow (CBF) was studied during hyperventilation (HV) recovery. Bilateral subdural temporal lobe CBF probes were placed for long-term monitoring. Epileptic cortex became ischemic as an inverse linear function of HV duration (r = 0.923, df = 9, P < 0.05). During 5 min recovery from 13 hyperventilation periods in 8 patients, mean CBF remained significantly reduced below baseline in epileptic versus non-epileptic temporal lobe (7.5 ± 2.4 vs 1.8 ± 0.9 ml/100gm-min below baseline, respectively, P < 0.05). Epileptic CBF response to HV reversal was an inverse and direct linear function of HV duration and focus ischemia during HV, respectively (r = 0.890, df = 9, P < 0.05 and r = 0.784, df = 5, P < 0.05, respectively). During HV recovery, nonepileptic CBF increased linearly with increasing HV duration (r = 0.782, df = 9, P < 0.05). The data suggest that epileptic cortex has abnormal vasomotor response to recovery from hyperventilation. We propose that abnormal cortical vasomotor control represents a fundamental pertubation in the pathogenesis of human epilepsy. Cortical vasomotor analysis may provide a new physiologic basis for localization of the epileptic focus.