Neuromodulation for Epilepsy

In patients with an unresectable epileptic focus, such as an undefined focus or epileptic focus within functional areas, various neuromodulation therapies, including vagus nerve stimulation, deep brain stimulation, and responsive neurostimulation, have been adopted as alternative treatment modalities. Vagus nerve stimulation, the earliest approved neuromodulation therapy in Japan, may be indicated irrespective of the epilepsy type and offers several advantages, including craniotomy not being required; however, its efficacy remains limited. Among deep brain stimulation targets, the anterior nucleus of the thalamus has the most established efficacy, and anterior nucleus of the thalamus-deep brain stimulation has been covered by the national health insurance system of Japan for the treatment of epilepsy since 2023. It is considered to be particularly effective for seizures originating from the limbic structures. Although it is not approved for insurance coverage in either Japan or the United States, another effective target is the centromedian nucleus of the thalamus, particularly for generalized epilepsies, including Lennox-Gastaut syndrome. While evidence is limited, deep brain stimulation targeting the hippocampus, subthalamic nucleus, pulvinar nucleus, posteromedial hypothalamus, nucleus accumbens, and cerebellum has also been reported. Responsive neurostimulation, though not yet approved in Japan, records electroencephalographic activity via intracranial electrodes and delivers automatic electrical stimulation upon seizure detection. It is useful for patients with an unresectable seizure focus, that is, eloquent cortex involvement or bilateral temporal lobe epilepsy. This review outlines neuromodulation therapies for epilepsy.