Large-field repetitive transcranial magnetic stimulation with circular coil in the treatment of functional neurological symptoms

Abstract

Patients with functional neurological symptoms (FNS) are frequently encountered by neurologists and are difficult to treat. Symptoms are multiple and may appear concurrently or successively in the same patient. To date, few studies have been published on focal repetitive transcranial magnetic stimulation (rTMS) in FNS. This type of stimulation induces a focal current, vertically in the cortex. Results are contradictory, probably because it is difficult to identify a limited cortical area that triggers these symptoms. We assessed the efficacy of another type of rTMS: large-field stimulation by means of a circular coil covering a surface area approximately 20 times greater and inducing a circular current tangentially to the cortex. We analysed two studies on the efficacy of large-field rTMS in functional paralysis and in functional movement disorders. The efficacy of large-field rTMS was very marked in these two studies. We reported several open series, including patients with functional sensory loss, functional visual loss, and non-epileptic seizures. For all patients, one or several sessions of 60 stimuli with circular coil were carried out with a protocol depending on the symptoms. The efficacy of large-field rTMS was dramatic in all patient series. Additionally, we discuss the possible involved mechanism: placebo effect, cognitive behavioural effect or neuromodulatory effect. According to the data from these different studies, large-field rTMS could be a new therapy for patients with FNS. However, controlled studies are mandatory.