Electronic aspects of spinal-cord stimulation in multiple sclerosis

Patients receiving chronic spinal-cord stimulation in the management of multiple sclerosis have been stimulated at a frequency of 33 Hz, with pulses whose duration has been varied between 0·05 ms and 2·0 ms. Measurements on the stimulating pulses show that the energy requirement was at a minimum when the pulse duration was 0·2 ms. The current and energy requirements of different patients using 0·2 ms pulses vary over a large range but measurement of the current requirement of a particular patient can be a useful observation in predicting his response to treatment: low current requirements are often associated with a good response and high currents with a poor response to treatment. The use of 0·2 ms pulses of the amplitude we have used meets the safety requirements established by other workers and our results indicate that this pulse duration is optimal in terms of safety requirements, as well as energy requirements.