The Triple Stimulation Technique: An Advanced Neurophysiological Method to Assess Motor Function in Multiple Sclerosis

Abstract

The triple stimulation technique (TST) is a collision method enabling study of motor conduction within the central nervous system. By combining transcranial magnetic stimulation of the cortex to peripheral nerve stimulation, this method markedly improves the evaluation of the corticospinal pathways. In multiple sclerosis (MS) and other disorders affecting central motor conduction, it allows accurate detection and quantification of the proportion of normally conducting axons and of motor conduction failures caused by conduction block, neuronal or axonal lesions. This review aims to (1) describe briefly the TST, its yield, strengths and limitations, (2) summarize the observations made in MS to date, (3) discuss the potential of the method. The TST is non-invasive and safe. Its practicability has been optimized by use of efficient software. Several studies have demonstrated that it is suitable to explore corticospinal conduction in MS, that its findings mirror the disability and clinical neurological signs of patients, and that it is reliable to evaluate follow-up and responses to treatments, including during the critical early stages of MS. We believe that the method is ready to be implemented to research and to routine clinical acquisitions. It should demonstrate useful to evaluate new therapies, monitor achievement of “no evidence of disease activity” (NEDA) and eventually to better understand neurodegeneration and repair in MS.