Spontaneous electromyographic activity in spinal cord lesions.

Different types of spontaneous activity may be found during electromyographic examinations in patients with spinal cord diseases. Syringomyelia and intramedullary tumor patients may show continuous motor unit activity, synchronous motor unit potentials, myokymic discharges, segmental and propriospinal myoclonus, and respiratory synkinesis. These types of discharges are less commonly encountered in other types of spinal cord lesions. It is suggested that the derangement of inhibitory mechanisms by a central spinal cord lesion may favor the appearance of abnormal spontaneous activity. An increase in the excitability of spinal motor neurons is probably the basic underlying mechanism.