Abstract
A case of steroid-resistant polymyositis showing periodic somnolence by Methotrexate therapy is reported.
A 51-year-old woman was diagnosed as polymyositis and steroid treatment was started in January, 1983. The improvement was not so sufficient that moderate doses of Methotrexate was initiated in November, 1983. In early March, 1984, periodic somnolence lasting 6 to 24 hours appeared and she could not recall her behavior during that time. When she was awake, EEG showed slight slow α activity with θ waves. And when she was somnolent, low voltage θ waves and 14Hz spindle-like waves were found. All-night sleep electroencephalogram revealed a remarkable increase in percentage of stage 1 sleep. On the other hand, the rate of the other stages, especially that of slow wave sleep, was decreased.
Once stopped, the Methotrexate therapy was resumed because of exacerbation. She developed prolonged somnolence accompanied by deterioration of her memory and character change. At the end of April, 1985, she deceased.
Pathological examination revealed polymyositis (marked atrophy of skeletal muscles), purulent myocarditis, fibrinous, purulent pericarditis, fibrinopurulent mediastinitis and multiple microabscesses in the brain. No bacteria was proved. Brain microabscesses were disseminated in frontal and occipital lobes, hippocampus, cerebeliar hemispheres, midbrain and pons. There were no pathological findings in thalamus, hypothalamus, reticular formation in brainstem and nucleus ceruleus. The formation of these brain microabscesses might have been preceded by the onset of somnolence.
The pathological substrate of somnolence cannot be explained. However the EEG records suggested moderate dysfunction of cerebral hemispheres and ascending reticular activating system, including raphe system and reticular formation in the midbrain.
There might be constitutional vulnerability to Methotrexate in this patient. If this therapy had been continued, the organic brain changes, reported as Methotrexate encephalopathy, would, have appeared.
