A ”biomarker” (or a biological marker) is something that can be objectively measured and can act as an indicator of a physiological or a pathological condition. For example, prostate specific antigen (PSA) is an enzyme that is normally present in the healthy prostate, but its levels are elevated in prostate cancer, serving as a useful biomarker. Another example is the measurement of blood sugar to diagnose diabetes.
In temporal lobe epilepsy, an event like penetrating head injury or meningitis can lead to spontaneous seizures (i.e., epilepsy) months to years down the line, but there is no way of predicting who will go on to develop epilepsy. If we had a biomarker, we could provide extra medical care to susceptible individuals and prevent spontaneous seizures. At present, anti-epileptic therapy is trial-and-error; if we found a biomarker, therapy could be more targeted and rational. It is no surprise then, that the pursuit for finding a biomarker for epilepsy is an area of active research. Some possible leads are as follows.
Molecular biomarkers: Brain cells that are injured can secrete a protein named S-100B, and eventually this protein can leak into the bloodstream. A recent study found that subjects with focal intractable epilepsy had higher levels of S-100B as compared to controls. If this research holds up, one can envision that a simple blood test can provide us clues about seizure severity and disease prognosis.
Scientists are also studying inflammation in epilepsy. Although we don’t know if this is true in human subjects, it has been found that the levels of some inflammatory markers are elevated in experimental rodents with epilepsy. More work needs to be done regarding the role of these markers in humans, but the research is quite intriguing!
EEG biomarkers: Researchers have proposed that abnormal brain activity called pathological high frequency oscillations (pHFOs) can serve as a biomarker for epilepsy, because these oscillations are recorded from seizure focus and are directly linked to seizure frequency. It is not fully understood how pHFOs are generated, but studies are underway to reveal potential mechanisms.
Imaging biomarkers: Seizures caused by fevers are known as febrile seizures, and, in some people, they can lead to temporal lobe epilepsy. Research suggests that it may be possible to look at certain parameters in MRI images to predict who will go on to develop epilepsy.