Longitudinal study of central motor conduction as a predictor of functional recovery after stroke

Abstract

Central motor conduction was assessed as a predictor of mortality and functional outcome in a longitudinal study of 118 patients with first-ever stroke. Investigations commenced 12-72 hours after stroke and were repeated up to death or 12 months. The results were compared with normal data, validated assessments of motor function, detailed neurological examinations and CT scans. Responses were recorded in the surface electromyogram from proximal and distal muscles of both upper limbs following percutaneous electromagnetic stimulation of the motor cortex (muscles contracted) and spinal motor roots (muscles relaxed). Central Motor Conduction Time (CMCT) was estimated by subtracting the latencies of spinal root evoked responses from those of cortical evoked responses. The durations and thresholds of the responses were recorded. Investigations 12-72 hours after stroke identified patients with 1) normal CIVICT, 2) delayed CIVICT, and 3) absent responses. Sequential investigations up to 12 months after stroke revealed 1) CIVICT may remain unchanged, 2) delayed CIVICT may become normal 3) responses may reappear with shortened duration, with delayed or normal CIVICT, 4) responses were lost if the stroke extended, 5) initially high thresholds to stimulation decreased. Absent responses 12-72 hours after stroke initially correlated with reduced power, hand dexterity and functional ability, and with large infarctions, mass effect and cortical lesions on CT scans. Normal CIVICT correlated with a high probability of survival and significantly better functional recovery at 12 months. Absent responses correlated with a high probability of stroke-related death. Survivors had poor outcome for muscle power, hand dexterity, activities of daily living, functional outcome and duration of stay in hospital. Results from the thenar muscles alone provided accurate prognostic information. If results from all the muscles were considered and the test repeated seven days after the first assessment, the sensitivity of the test increased. Electromagnetic stimulation is a safe prognostic investigation that is complementary to clinical examination and imaging patients with stroke.