Abstracts

Rationale: A preictal state exists minutes or hours prior to the clinical seizure. Functional MRI, SPECT, transcranial magnetic stimulation and direct cortical recordings show preictal changes in cerebral blood flow, oxygenation and cortical excitability. We investigated whether hemodynamic changes preceding temporal lobe seizures were detectable in frontal scalp recordings using near infrared spectroscopy (NIRS). Patients undergoing video-EEG telemetry (VET) for inpatient pre-surgical workup were studied.Methods: A NIRS sensor was placed over the frontal scalp ipsilateral to the patient s first recorded seizure. Regional cerebral oxygenation (rSO2) was recorded synchronously with VET data and peripheral oxygen saturation (SaO2) using digital pulse oximetry. Periictal changes in rSO2 were compared with baseline interictal rSO2. Results: Eleven subsequent seizures were recorded in six patients with temporal lobe epilepsy. A mean peak preictal increase in rSO2 of 7.1% relative to interictal baseline (p<0.001) occurred at a mean peak latency of 298.9 seconds before seizure onset. The preictal increase was followed by decrease in rSO2 in proximity to seizure onset. SaO2 decline started at a mean latency of 69 seconds following rSO2 decrease. Lastly, a postictal increase in rSO2 occurred with a mean duration of about 32 minutes. Periictal rSO2 changes occurred with both ipsi and contralateral temporal lobe seizures.Conclusions: We have shown that a preictal change in cerebral oxygenation can be detected noninvasively with a mean peak latency of about 4.98 minutes before seizure onset. NIRS technology has the potential, in the ambulatory setting, for providing a signal of an imminent seizure.