Characteristics of tetanic muscle contraction in Parkinson patients

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Abstract
The aim of this study was to examine contraction characteristics in striated muscles from Parkinson patients and to measure any changes in characteristics based on changes in medication. Fifteen patients, 9 men and 6 women, mean age 61.6 (range 43-70) with mild to moderate parkinsonism, (Hoehn and Yahr I-III) were investigated, and the results were compared with a group of 8 normal controls (mean age 59.6, range 50-70). Twelve of the patients (7 men and 5 women) were also tested after a 24-h period without medication. Using supramaximal electrical stimulation of the ulnary nerve at the wrist contraction, characteristics in the m. adductor pollicis muscle can be recorded. Stimulation results were printed on a fast paper writer. The following characteristics were recorded: 1) electromechanical delay of contraction EMDc; 2) contraction time to half tetanus CTT1/2; 3) electromechanical delay of relaxation EMDr; 4) relaxation rate RR for 10 ms RR-10; 5) the force produced in the tetanic contraction at stimulus frequencies 5, 10, 20, 50 Hz. The results showed that the in initiation of contraction (EMDc) was normal compared with controls. CTT1/2 was shorter (p less than 0.001) in the group of Parkinson patients compared with normals. EMDr was not changed when compared with normals, but RR-10 was increased, p less than 0.05. Force levels at the different stimulation rates were not significantly changed. After withdrawal of medication all parameters were unchanged. Muscle contraction characteristics in tetanic contraction were found to be abnormal indicating either a possible preactivation in the muscle contraction or a secondary change in the muscles of patients with Parkinson's disease.