The motor unit in psychotic patients: a single fibre EMG study.

Abstract

SUMMARY Single fibre EMG recording from extensor digitorum communis muscle is described in patients with psychotic illness. The fibre density, or average number of single muscle fibre action potentials belonging to the same motor unit within the uptake area of the electrode, was higher in the patient group than in normal controls. Increased jitter was occasionally seen. Motor and sensory nerve conduction velocity values were within the normal range. The results indicate that psychosis is associated with denervation and reinnervation by collateral sprouting.

Single fibre electromyography in central core disease

“…The increased motor unit fibre density in central core disease is less than the values observed in progressive diseases of the lower motor neurone (Table 2), but similar to those described in mild or moderately severe axonal neuropathies . Increased terminal innervation ratio is well correlated with increased fibre density of the motor unit in lower motor neurone diseases , and other processes such as in psychotic patients (Crayton et al, 1977). In our series of cases of central core disease, the average value of the motor unit fibre density was increased by 46%, and the terminal innervation ratio was increased by 20-30% in the cases of Isaacs et al (1975) andCoers et al (1976).…”

Fine Motor Performance in Schizophrenia

“…Meltzer and Crayton [8] first noted biopsy findings of increased subterminal motor-axon branching in schizophrenic patients, which was not related to medication dosage. A follow-up study replicated this finding and extended the testing to family members, a portion of whom also demonstrated this innervation abnormality [9], Single-fiber electromyogra phy studies of the extensor digitorum communis demon strated findings of increased fiber density, which is an EMG measure consistent with increased subterminal nerve branching [ 10], This finding of increased subtermi nal axon branching is a pattern which is consistently dem onstrated in the process of peripheral nerve regeneration after muscle denervation. In addition to subterminal mo tor-axon studies, muscle fiber studies have been per formed.…”

Massive serum creatine kinase increases with atypical antipsychotic drugs: what is the mechanism and the message?

“…Branching and sprouting of subterminal motor nerves were also found, providing clear evidence of neuroplasticity in some patients with these disorders (Meltzer and Crayton 1974). Abnormalities in motor unit territories were also found (Crayton et al 1977).…”