The therapeutic use of non-invasive brain stimulation in multiple sclerosis – a review

Abstract

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system and a leading cause of disability in young adults. Many disabling symptoms in MS, such as spasticity, pain, depression and cognitive deficits are not fully controlled by drug treatment. Non-invasive brain stimulation (NIBS) techniques can be used as tools for modulating altered cortical excitability and plasticity MS patients, providing an improvement in disabling symptoms affecting such patients. This review reported and summarized some of the most interesting and promising recent achievements regarding the therapeutic use of NIBS in MS patients. We reviewed the clinical application of transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS), emphasizing their effect on clinical symptoms and signs that are commonly involved in MS patients. In addition, we shortly described new NIBS protocols, such as transcranial alternating current stimulation and transcranial focused ultrasound stimulation as potential and innovative therapeutic options to be applied in future studies in MS patients. We reviewed twenty-one studies covering six main clinical domains. Most of such studies focused on fatigues (33.3%), motor performance (19%) and spasticity (19%), sparse results were about pain (9.5%), cognitive abilities (9.5%), sensory deficit (4.8%) and bladder function (4.8%). The most promising results have been published for the improvement of motor (i.e. hand dexterity) and cognitive performances (i.e. attention and working memory) by applying rTMS or tDCS alone or in association with motor/cognitive training, for pain's treatment by using tDCS. There are still no official recommendations for the therapeutic use of tDCS or rTMS in MS. The huge inter-individual variability of NIBS efficacy is still a big challenge which needs to be solved. However, well-designed studies, deeper knowledge about pathomechanisms underlying MS, and the combination of such techniques with motor and cognitive rehabilitation might results in higher effectiveness of NIBS.