Functional neurological disorder (FND) is a condition that causes significant suffering and disability, as well as considerable cost to society. It is defined by the presence of neurological symptoms that interfere with an individual's functioning and are not consistent with any known anatomical lesion. Motor FNDs, i.e., those with motor neurological symptoms, are the best defined. In recent years, much progress has been made in terms of recognition, diagnosis, and medical care. However, in terms of treatment, the options remain limited.
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive and acceptable treatment that has proven effective in certain chronic pain conditions, depression, and OCD. It involves applying repeated magnetic pulses to a specific area of the brain in order to modify the electrical current in the concerned area and the connectivity of associated regions. Several studies have shown the effectiveness of this therapy in patients with FND, although discrepancies remain, particularly in the neuroanatomical target and evaluation criteria.
Recent advances in neuroimaging of FNDs have led to a better understanding of the pathophysiology of FNDs and have resulted in certain recommendations for the clinical evaluation of FNDs in research. The most widely shared theoretical model of motor FNDs is that of movement prediction. It suggests a predominant role for the right temporo-parietal junction (rTPJ) in FNDs.
From a neuroimaging perspective, Voon et al. demonstrated in 2010 that eight subjects with functional tremors exhibited hypoactivity in the rTPJ. This area of the brain appears to be strongly involved in the sense of agency, yet this function is impaired in subjects with FND. A study of seven patients with FND of the dissociative functional seizure type showed a reduction in the number of seizures per week following 30 sessions of rTMS targeting the rTPJ at an excitatory frequency.
More recently, S. Aybek's team demonstrated a change in brain activity in the rTPJ in a fMRI in patients with FND after a session of theta burst (tb) rTMS. Theta burst stimulation allows for more effective stimulation in a shorter time. The intermittent excitatory tb-rTMS protocol showed a tendency to increase the rTPJ activity. In this study, tolerance was evaluated as a secondary outcome measure. No adverse effects were reported other than asthenia and headaches, which are well-known and documented adverse effects of rTMS.
As part of its referral care program, the University Hospital Department of Adult Psychiatry at the Guillaume Regnier Hospital Center in Rennes receives patients suffering from FND who have been referred by their attending physicians and for whom rTMS treatment may be indicated. These patients undergo a course of 40 rTMS sessions in theta burst mode targeting the rTPJ. Taking into account the latest recommendations for the assessment of FNDs in research, the investigators wish to analyze the impact of this treatment on the overall impression of change perceived by the patient and the physician after one month (the date at which the effects of rTMS are supposed to be most apparent). Secondarily, the investigators wish to evaluate the impact of the rTMS treatment on the motor and non-motor symptoms of FNDs, such as agency, in order to better understand the pathophysiology, and also to evaluate the impact on quality of life.
