Central motor conduction examined with the triple stimulation technique correlates with pyramidal tract dysfunction and disability in patients with multiple sclerosis

Abstract

Inflammatory lesions and axonal degeneration of central motor conduction pathways result in gait disturbance and contributes particularly to increasing disability in patients with multiple sclerosis. With conventional transcranial magnetic stimulation central conduction times can be estimated but axonal damage or conduction block of motor pathways is less sensitively detected to correlate well with disability. The triple stimulation technique (TST) examines the corticospinal tract by magnetic stimulation of cortical motor areas followed by sequenced distal and proximal peripheral nerve electric stimulation. The originating potential is a result of the collison of the sequenced stimuli. Then the TST-potential is compared with sequential stimulation of peripheral nerves alone. With the resulting amplitude ratio central conduction failure can be quantified by TST.