Muscle biopsy, macro EMG, and clinical characteristics in patients with schizophrenia

In a previous study of motor unit properties in patients with schizophrenia, muscle fiber histologic and electrophysiologic abnormalities were observed. The present study was designed to compare patients with schizophrenia with healthy control subjects with regard to muscle fiber histology and motor unit function. A second objective was to relate these variables to clinical characteristics.

Twelve patients with first-episode schizophrenia and fifteen patients with chronic schizophrenia (DSM-III-R) and 27 matched control subjects were included in the study. Muscle biopsies were performed either in m. tibialis anterior or m. vastus lateralis. Electromyographic recordings (macro EMG) were made from the m. tibialis anterior motor units. Psychiatric ratings included the PANSS and extrapyramidal side effects.

Seven of the muscle biopsy specimens from the patients and one from the control subjects were classified as abnormal (p =.049). The most frequent abnormality was atrophic muscle fibers. Eight patients and no control subjects exhibited pathological macro EMG (p =.032). The findings were present in chronic as well as in first-episode patients with schizophrenia.

In approximately 50% of the patients, neuromuscular abnormalities were found either in the muscle biopsy or the macro EMG investigations. The results indicate that either a common pathologic process or different pathological processes are at hand in the neuromuscular system in patients with schizophrenia. The findings are compatible with a disturbed cell membrane function.