Lithium and peripheral nervous system function in manic-depressive patients

Lithium salts are widely used in treatment of affective disorders, but lithium may cause electrophysiologically detectable changes in peripheral nervous system even with lithium concentrations within recommended therapeutic limits. The risk of lithium treatment against other risks to peripheral nervous system in psychiatric patients with affective psychoses was tested in our study.

Electrophysiologic parameters of motor and sensory peripheral nerve fibre function were measured in two age-matched groups of psychiatric patients (20 lithium-treated and 20 affective psychotic patients without lithium treatment) and a group of 20 healthy age-matched volunteers.

Lower amplitudes of M waves (p < 0.015) and sensory nerve action potentials (p < 0.020) on stimulation of the median nerve have been found in both groups of patients. On peroneal nerve stimulation lower M wave amplitudes have been found only in the group of lithium-treated patients (p < 0.055). No significant differences in conduction parameters of motor and sensory fibres were demonstrated.

Our results demonstrate subclinical involvement of motor and sensory axons in affective-psychotic patients, which is only slightly more pronounced in lithium-treated patients. We suggest that lithium (within therapeutic plasma concentrations) is just one among the factors leading towards minor axonopathy in psychiatric patients.