Epilepsy
Epilepsy is a neurological disorder characterised by the long-term risk of recurrent seizures of an unknown cause. Epileptic seizures show an excess of abnormal neuronal activity in the cortex of the brain, which can be confirmed with an electroencephalogram (EEG) recording. Once this abnormal brain activity occurs it may spread to different brain areas and typically results in seizures. The most common seizures are convulsive but some are ‘absence’ seizures, where the patient loses consciousness for brief periods.
Epilepsy affects over 70 million people in the world but is not always a lifelong condition. In fact, many patients can actually be treated with anti-convulsant medications for effective management. Some patients may take several (2-3) types of anti-epileptic medications to reduce the number of seizures but there is a greater likelihood of side effects due to higher doses of medications used. For approximately 30% of epilepsy sufferers, they continue to experience seizures and are known as ‘drug-resistant’ patients and there are less treatments available for such cases.
Neurosurgery
Only a small fraction of epilepsy patients are suitable for a neurosurgical approach due to the high invasiveness. One neurosurgical treatment option is to remove the area of the brain where seizure originates, thereby blocking the spread of the abnormal brain activity to other regions.
Deep Brain Stimulation (DBS)
Deep brain stimulation is an invasive neuromodulation application that can used to treat epilepsy. This approach requires electrodes to be implanted into the brain in neurosurgery, which are then attached to an Implanted Pulse Generator (IPG) that is placed underneath the skin above the chest cavity. Electrical stimulation supplied into the brain through the electrodes disrupt the abnormal brain activity and help reduce the number of seizures experienced by the patient.
Vagus Nerve Stimulation (VNS) – Invasive
VNS is another neuromodulation technique. Following the surgical procedure and implantation of the impulse generator (please see above), electrical stimulation delivered to the vagus nerve modulates the neuronal activity which is relayed to the brainstem, specifically the Nucleus Tractus Solitarii (NTS), then leading to the activation of higher brain areas. The resultant effect is a reduction in seizures for epileptic patients and is typically effective in 40-60% of patients.[1]
Transcutaneous Vagus Nerve Stimulation (tVNS) – Non-invasive
tVNS is a non-invasive neuromodulation technique for stimulating the vagus nerve through the skin. In NEMOS® therapy, gentle electrical impulses are delivered to the outer auricle via a special ear electrode connected to an external stimulator that is carried by the user. The electrical impulses have been optimized to specifically activate the Auricular Branch of the Vagus Nerve (ABVN), which are relayed to the Nucleus Tractus Solitarii (NTS) of the brainstem and then to higher brain areas such as the Locus Coeruleus and Dorsal Raphe. This neuromodulated activity results in clinical benefits with a reduced number of seizures experienced by the patient.
References
[1] Johnson and Wilson. J Inflamm Res 2018;11:203-123
