NERVE STIMULATOR

Typical Number in Hospital: 12

Cost Bands: 2,3

References: 3

Electrical stimulation of nerves is performed for a variety of reasons. Anaesthetists use battery-operated stimulators which present short-duration high-voltage pulses to the skin to determine whether the effect of muscle relaxants used during surgery is sufficient to suppress all function of the voluntary muscles. Stimulators which may affect the nerves are also used for the relief of pain. These use lower voltages and do not usually cause muscle contraction. In the physiotherapy department electrical stimulators are widely used in order to exercise muscles: whether they act directly on the muscle or via nerves is probably not important.

Nerve stimulators are also used in a range of diagnostic procedures. In the neurology department nerves are stimulated via skin electrodes or via needle electrodes which may be placed right into the nerve trunk. A typical reason for stimulating the muscle in this way is to establish the conduction velocity of the longer nerves, which is diagnostic of certain diseases, and a low velocity may suggest that the nerve is trapped at some point. Most conduction velocity tests are performed on the efferent (motor) nerves but the same stimulation can be applied to the afferent (sensory) nerves, but this is less often done since the response further along the nerve is more difficult to detect.

A nerve stimulator consists of a pulse generator of variable rate, a pulse length controller, an amplifier, and an isolating circuit. Cardiac pacemakers may also be considered to be nerve stimulators.