A Case of Psychogenic Myoclonus Responding to a Novel Transcranial Magnetic Stimulation Approach: Rationale, Feasibility, and Possible Neurophysiological Basis

Abstract

Repetitive transcranial magnetic stimulation (rTMS) can relieve motor symptoms related to psychogenic movement disorders (PMDs), but the subtending neurophysiological basis is unclear. We report on a 50-year-old woman with a diagnosis of psychogenic myoclonus in the right lower limb, who was treated with a daily session (in the late morning/early afternoon) of 1 Hz rTMS over the left premotor cortex (PMC), five times a week for 6 weeks. Clinical data and EEG at rest were collected before and immediately and 2-month after the rTMS protocol completion. The patient reported a significant reduction of involuntary movement frequency and intensity and the related disability burden up to the follow-up. In parallel, any abnormality in terms of source current density within and connectivity between the frontal and parietal areas was reset. The short follow-up period, the lack of extensive neurophysiological measures, and the lack of control treatment represent the main limitation of the study. However, lowfrequency rTMS over PMC seems a safe and promising approach for the management of psychogenic myoclonus owing to the combination of cortical neuromodulation and non-specific mechanisms suggesting cognitive-behavioral effects.

Neurostimulation for the treatment of functional neurological disorder: A systematic review

“…In the majority of studies, the motor cortex was selected as target site, despite lack of motor cortex abnormalities in patients with FND based on a large body of neurophysiological and neuroimaging studies (for a review see Spagnolo, Garvey and Hallett, 2021 [56] ). Current evidence suggests that functional neurological symptoms are associated with abnormalities in activity and connectivity in motor-limbic circuitry (i.e., amygdala, insula, supplementary motor area) as well brain areas implicated in agency (right temporoparietal junction – rTPJ– and precuneus) [60] , [61] . Therefore, modulation of these areas via NIBS may represent a novel and effective therapeutic strategy for FND.…”

“…Case Reports Parameters of stimulation Results Study (author/year) FND Phenotype Design N Anatomical Target Frequency* Intensity (% MT) Total pulses/ session # Sessions Outcome Measures Outcome Time point 1** Outcome Time point 2*** Case Reports Bottemanne et al [66] Tetraparesis Mixed Tremors Functional Seizures Case report 1 MC rTMS 1Hz 150% 300 pulses 20 sessions 2 sessions/day 10 days MRC Symptoms improved between 8th and 12th session, with paresis improving first. At 2 months - resolution of all functional neurological symptoms Naro et al [61] Functional myoclonus Case report 1 Left PMC rTMS 1Hz 115% RMT 1,200 pulses 30 sessions 6 weeks 5 sessions/ week EEG EMG Magnitude and frequency of the myoclonus were strongly reduced based on EMG data Patient-reported improvement in myoclonus severity after 2 weeks of rTMS treatment. This improvement consolidated at the end of the rTMS paradigm and persisted up to 2 months later.…”

“…The majority of the studies included in our review evaluated TMS effects on functional motor disorders (FMD) with negative symptoms (paresis, weakness, paralysis, myoclonus) (see Table 1 ). In these trials, the primary motor cortex contralateral to the symptom (bilateral in the case of bilateral motor symptoms) represented the most frequently selected anatomical target, with the exception of 2 studies in which the premotor cortex – contralateral to the affected limb [35] , [61] – and the vertex [42] were stimulated.…”

Use of non-invasive neurostimulation for rehabilitation in functional movement disorders

“…After 36 sessions, the patient showed a reduction in depression, anxiety and dystonia measured by the Beck Depression Inventory 2 (BDI-2), Generalized Anxiety Disorder 7 (GAD-7), Patient Health Questionnaire 9 (PHQ-9), Beck Anxiety Inventory (BAI), Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), and a perception of improvement evaluated by the CGI ( 35 ). In another case report, a patient with functional myoclonus in the right lower limb was treated with daily sessions of 1 Hz rTMS with 1,200 biphasic magnetic pulses over the left PMC five times a week for 6 weeks, with a significant reduction in frequency and intensity of the involuntary movements for up to two months as measured by the Unified Myoclonus Rating Scale (UMRS) ( 36 ). One patient with an unusual presentation of functional tetraparesis, mixed tremors and functional seizures was treated with biofeedback psychotherapy together with rTMS (20 sessions, two sessions per day for 10 days; 1 Hz, 150% RMT, 20-minute sessions, 300 pulses per session).…”