MicroRNAs as potential biomarkers in temporal lobe epilepsy and mesial temporal lobe epilepsy

Temporal lobe epilepsy is the most common form of focal epilepsy in adults, accounting for one third of all diagnosed epileptic patients, with seizures originating from or involving mesial temporal structures such as the hippocampus, and many of these patients being refractory to treatment with anti-epileptic drugs. Temporal lobe epilepsy is the most common childhood neurological disorder and, compared with adults, the symptoms are greatly affected by age and brain development. Diagnosis of temporal lobe epilepsy relies on clinical examination, patient history, electroencephalographic recordings, and brain imaging. Misdiagnosis or delay in diagnosis is common. A molecular biomarker that could distinguish epilepsy from healthy subjects and other neurological conditions would allow for an earlier and more accurate diagnosis and appropriate treatment to be initiated. Among possible biomarkers of pathological changes as well as potential therapeutic targets in the epileptic brain are microRNAs. Most of the recent studies had performed microRNA profiling in body fluids such as blood plasma and blood serum and brain tissues such as temporal cortex tissue and hippocampal tissue. A large number of microRNAs were dysregulated when compared to healthy controls and with some overlap between individual studies that could serve as potential biomarkers. For example, in adults with temporal lobe epilepsy, possible biomarkers are miR-199a-3p in blood plasma and miR-142-5p in blood plasma and blood serum. In adults with mesial temporal lobe epilepsy, possible biomarkers are miR-153 in blood plasma and miR-145-3p in blood serum. However, in many of the studies involving patients who receive one or several anti-epileptic drugs, the influence of these on microRNA expression in body fluids and brain tissues is largely unknown. Further studies are warranted with children with temporal lobe epilepsy and consideration should be given to utilizing mouse or rat and non-human primate models of temporal lobe epilepsy. The animal models could be used to confirm microRNA findings in human patients and to test the effects of targeting specific microRNAs on disease progression and behavior.