Action Potentials of Muscles in Rigidity and Tremor

Rigidity and alternating tremor of antagonist muscles are the two presenting symptoms of paralysis agitans, whether of the senile (usually arteriosclerotic) or of the juvenile and presenile (usually postencephalitic) type. Either symptom may exist without the other, or either one or both may be unilateral or restricted to a single extremity. Rigidity may imitate the spasticity of patients who suffer from hemiplegia or paraplegia, and though voluntary movement is usually possible. the motor performance of patients afflicted with rigidity may for practical purposes amount to "unmistakable paresis," as Foerster has expressed it.1Tremor and rigidity exist in conditions other than paralysis agitans. They appear, however, to be linked in this disease in a specific way. It has been one of the purposes of this investigation to elucidate the underlying mechanism of this linkage. Rigidity, tremor and reflexes under various conditions were therefore studied by means of electromyography. Studies of