Non-Invasive Brain Stimulation in Conversion (Functional) Weakness and Paralysis: A Systematic Review and Future...

Area of Science:

• Neurology
• Neuroscience
• Psychiatry

Background:

• Functional weakness (FW) is a debilitating condition often requiring multidisciplinary treatment.
• Non-invasive brain stimulation (NIBS) methods like electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS) have been explored for FW.
• Existing treatments typically combine behavioral approaches with motor learning programs.

Purpose of the Study:

• To systematically review the literature on NIBS methods (ECT, TMS, tDCS) for treating FW.
• To retrospectively assess symptom changes using Clinical Global Impression scale-Improvement (CGI-I) scores.
• To elucidate the potential role of NIBS in FW and recommend future study designs.

Main Methods:

• Systematic literature review of PubMed and Web of Science for studies using NIBS (ECT, TMS, tDCS) in FW patients.
• Retrospective determination of nominal CGI-I scores from case narratives to quantify symptom improvement.
• Analysis of identified studies focusing on patient numbers, treatment methods, and reported outcomes.

Main Results:

• Two case reports on ECT and five studies on TMS (86 patients) were identified; no tDCS studies were found.
• Repetitive TMS (rTMS) showed satisfactory short-term improvement in 75/86 patients, with 72% achieving "very much improved" (CGI-I=1).
• No severe adverse effects were reported for rTMS; ECT showed short-term response but symptom deterioration at follow-up.

Conclusions:

• NIBS, particularly rTMS, demonstrates potential for short-term improvement in FW symptoms, though long-term efficacy is unclear.
• The limited number and poor quality of existing studies warrant caution when assuming a beneficial effect of NIBS in FW.
• Further high-quality research with robust study designs is recommended to establish the efficacy of NIBS for functional weakness.