Objective
We studied the prevalence of abnormal spontaneous activities in hemiplegic upper limbs, its nature and correlation with various clinical features.

Method
Forty-seven patients with hemiplegia from various central nerve system disease within about four months from disease onset were included in the study. The patients who showed obvious clinical evidence of peripheral nerve system disease were excluded. Motor and sensory nerve conduction studies (NCS) of median and ulnar nerves in hemiplegic limbs and motor nerve conduction studies of axillary nerve in both side were done. The cases demonstrating abnormal NCS were excluded in data analysis. Needle electromyography (EMG) was done in proximal muscles (deltoid, supraspinatus, infraspinatus, biceps brachii) and distal muscles (abductor pollicis brevis, abductor digiti quinti and first dorsal interosseous). Muscle strength of shoulder abduction and mass grasp were measured by manual muscle test. Development of shoulder hand syndrome was investigated through clinical examination.

Results
Mean period from onset of hemiplegia to EMG examination was 45.2⁑23.8 days (8∼108 days). Abnormal spontaneous activities were observed in 78% of patients in one of the muscles examined and were found more frequently in distal muscles than proximal muscles. Frequency of spontaneous activities was not significantly related to the time after onset of disease during the first 4 months. Spontaneous activities were more frequently observed in distal muscles with strength of less than good or fair grade. Patients with spontaneous activities showed tendency to higher incidence of shoulder hand syndrome but there was no statistical significance.

Conclusion
Hemiplegic upper limbs showed frequent abnormal spontaneous activities without definite peripheral nerve involvement. Its unique pattern of distribution should be kept in mind when we meet hemiplegic patients in electromyographic consultation.