Treatment of epilepsy can be considered generally as medical or surgical. Anti-epileptic drugs achieve a five-year seizure freedom in 54-70% patients. It is estimated that 50-90% of patients with drug-refractory epilepsy may not be candidates for resective surgery. For example, surgery may not be offered because of the proximity of the primary seizure focus to eloquent cortex or the inability of investigations to identify a circumscribed epileptogenic zone. In such cases, neuromodulation devices may be considered. Open-loop devices have pre-programmed stimulation and are independent of brain state. Closed-loop devices have a detection (onset of ictal event in epilepsy) and stimulation component. Open-loop devices include vagus nerve stimulation (device implanted in left chest and lead attached to left vagus nerve), deep brain stimulation (device implanted in the chest and leads attached in the brain parenchyma targeting the thalamus) and trigeminal nerve stimulation (external pulse generator and transcutaneous electrodes to supraorbital branches of trigeminal nerve). Reduction in seizure activity ranged from 25%-41% at one year. Deep brain stimulation five-year reduction 69%. Closed-loop device comprises an implantable neurostimulator with lead placement within the estimated epileptogenic zone or at the seizure-onset zone (identification requiring a combination of imaging and invasive and noninvasive diagnostic modalities). Reduction in seizure activity was 41% at one year and 53% at two years. Evidence suggests that their therapeutic benefit is achieved through modulation of seizure networks. The improvement in outcomes achieved combined with its minimally invasive, non-destructive nature make closed-loop stimulation a promising therapy. This article highlights that neuromodulation may become more widely utilised for the treatment of epilepsy. The shared space within the head and neck for such devices and their potential presentation to the ENT surgeon should be observed.
Neuromodulation in drug resistant epilepsy
Reviewed by Aaron Ferguson
Neuromodulation of Epilepsy Networks.
