Broadband-NIRS System Identifies Epileptic Focus in a Child with Focal Cortical Dysplasia-A Case Study

Epileptic seizures are transiently occurring symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Previous functional near-infrared spectroscopy (fNIRS) studies during seizures have focused in only monitoring the brain oxygenation and haemodynamic changes. However, few tools are available to measure actual cellular metabolism during seizures, especially at the bedside. Here we use an in-house developed multichannel broadband NIRS (or bNIRS) system, that, alongside the changes in oxy-, deoxy- haemoglobin concentration (HbO(2), HHb), also quantifies the changes in oxidised cytochrome-c-oxidase Delta(oxCCO), a marker of cellular oxygen metabolism, simultaneously over 16 different brain locations. We used bNIRS to measure metabolic activity alongside brain tissue haemodynamics/oxygenation during 17 epileptic seizures at the bedside of a 3-year-old girl with seizures due to an extensive malformation of cortical development in the left posterior quadrant. Simultaneously Video-EEG data was recorded from 12 channels. Whilst we did observe the expected increase in brain tissue oxygenation (HbD) during seizures, it was almost diminished in the area of the focal cortical dysplasia. Furthermore, in the area of seizure origination (epileptic focus) Delta oxCCO decreased significantly at the time of seizure generalization when compared to the mean change in all other channels. We hypothesize that this indicates an incapacity to sustain and increase brain tissue metabolism during seizures in the region of the epileptic focus.

Automated summary

This study used bNIRS technology to measure metabolic activity and brain tissue hemodynamics/oxygenation during epileptic seizures in a 3-year-old girl with extensive malformation of cortical development. The results showed an increase in brain tissue oxygenation during seizures, but little change in the area with developmental abnormalities. Additionally, in the epileptic focus area, cellular oxygen metabolism significantly decreased during seizure generalization, suggesting an inability to sustain and increase brain tissue metabolism during seizures.