Neurophysiological investigations in restless legs syndrome and other disorders of movement during sleep.

Besides polysomnographic techniques, other neurophysiological methods have been utilized in order to understand the pathophysiology of restless legs and periodic limb movement syndromes. By using electromyography with nerve conduction velocity (EMG-CV) and somatosensory evoked potentials (SEPs) it has been possible to determine how frequently each muscle was involved in periodic limb movements, how frequently EMG activity started in a given muscle and the time delay and pattern of activation between the first and the other activated muscles. The etiology of symptoms does not involve structural lesions since brainstem and spinal pathways are intact. Recent evidence from paired transcranial magnetic stimulation suggests that the pathophysiological key in sleep motor disorders is a modified global excitability of corticospinal pathways. The next neurophysiological goal will be to localize the unresolved anatomical level of sleep disorder movement generators and to describe their mechanism.