Lights for epilepsy: can photobiomodulation reduce seizures and offer neuroprotection?

Abstract

Epilepsy is synonymous with individuals suffering repeated "fits" or seizures. The seizures are triggered by bursts of abnormal neuronal activity, across either the cerebral cortex and/or the hippocampus. In addition, the seizure sites are characterized by considerable neuronal death. Although the factors that generate this abnormal activity and death are not entirely clear, recent evidence indicates that mitochondrial dysfunction plays a central role. Current treatment options include drug therapy, which aims to suppress the abnormal neuronal activity, or surgical intervention, which involves the removal of the brain region generating the seizure activity. However, ~30% of patients are unresponsive to the drugs, while the surgery option is invasive and has a morbidity risk. Hence, there is a need for the development of an effective non-pharmacological and non-invasive treatment for this disorder, one that has few side effects. In this review, we consider the effectiveness of a potential new treatment for epilepsy, known as photobiomodulation, the use of red to near-infrared light on body tissues. Recent studies in animal models have shown that photobiomodulation reduces seizure-like activity and improves neuronal survival. Further, it has an excellent safety record, with little or no evidence of side effects, and it is non-invasive. Taken all together, this treatment appears to be an ideal treatment option for patients suffering from epilepsy, which is certainly worthy of further consideration.

Keywords: cell death; gliosis; inflammation; infrared; mitochondria; non-pharmacological; red; seizure.

Figure 1

Schematic diagrams of the major abnormalities evident in epilepsy (left side) as compared with normal, and after photobiomodulation treatment (right side). Epilepsy is characterized by abnormal and excessive cell activity (represented by thick processes from pyramidal or round somata), mitochondrial dysfunction and oxidative stress and reduced glucose metabolism (represented by all the red somata), interneuron dysfunction (represented by thick processes and red round somata), synaptic imbalance and increase in glutamate in extracellular space (represented by yellow shade), cell death (represented by fewer cells compared to normal side), gliosis and inflammation (represented by small pink cells). For this schematic, for the sake of clarity, abnormalities are spread across the hippocampus and cortex. Recent evidence in animal models of epilepsy indicates that photobiomodulation (PBM) can improve many, if not all, of these abnormalities (represented by all the thinner processes and green cells on the right side of the schematic diagram), restoring to normal.

Figure 2

Schematic diagrams of the effect of photobiomodulation on (A) distressed neurons and (B) healthy neurons. In distressed neurons (indicated by red mitochondria, misshaped red soma, and short processes), photobiomodulation improves neuronal health (green soma) by increasing mitochondrial activity (green mitochondria), growth factor and gene expression, ATP (energy) levels and overall functional activity. It also reduces reactive oxygen species levels, and the surrounding inflammation and gliosis (small pink cells). In healthy neurons, photobiomodulation can either generate an increase in activity or a decrease, depending on the cell group and/nervous system involved.