Near-infrared spectroscopy shows preictal haemodynamic changes in temporal lobe epilepsy

Growing evidence suggests that focal seizures are preceded by haemodynamic changes. Specifically, changes in cerebral blood flow, blood oxygen level-dependent magnetic resonance imaging, and near-infrared spectroscopy measurements of haemoglobin have been observed in the seizure focus and other brain regions many minutes prior to the onset of spontaneous seizures. The purpose of this study was to detect preictal haemodynamic changes using near-infrared spectroscopy, a portable and non-invasive optical technique that measures changes in cerebral haemoglobin.

Five subjects with temporal lobe seizures were studied using near-infrared spectroscopy until a seizure was observed, as confirmed by electroencephalography or clinical symptoms. Relative changes in oxy- and deoxyhaemoglobin, total haemoglobin, and blood oxygen saturation were assessed in the anterior frontal lobes between 15 minutes and one minute prior to seizure onset.

In all subjects, a decrease in oxyhaemoglobin, total haemoglobin, and oxygen saturation was observed in the frontal lobe, ipsilateral to the presumed seizure focus. On the contralateral side, all subjects showed a decrease in relative oxyhaemoglobin content. No consistent change in deoxyhaemoglobin was seen on either side.

Preictal haemodynamic changes can be detected in the frontal lobes using near-infrared spectroscopy. Our results suggest that a decrease in metabolic rate, and thus neuronal activity, occurs in the ipsilateral frontal lobe prior to the onset of temporal lobe seizures. Extratemporal haemodynamic changes may therefore be an important marker for seizure anticipation.