Akinesia in Parkinson's disease

IN 3 of 5 patients described by Parkinson1 in 1817, weakness and profound muscular fatigue were conspicuous symptoms in addition to tremor and rigidity. In 1925, Kinnier Wilson2 further emphasized this striking di5culty in motor strength and endurance in patients with parkinsonism but could not specifically correlate it with either rigidity or amount of tremor present. He commented, “It seems as if the patient does not care to continue the task or put an adequate amount of effort into a particular movement.” No pathologic evidence exists that any break occurs in the continuity of the voluntary motor system such as is found in pyramidal tract disease caused by stroke or in lower motor neurons affected by neuritis or poliomyelitis. Strong motivation in the ordinary patient with Parkinson’s disease will produce a perfectly normal level of muscle power. Therefore, the word paralysis in the term paralysis agitans is not really justified. For this study of akinesia, we have developed a special, accurate ergograph in which the first dorsal interosseous muscle in the hand is specifically studied. The rest of the hand and wrist are held in a fixed position. The patient can, by using this muscle, abduct his index finger toward his thumb, pulling a lever on which is an adjustable weight. The movement of the finger is registered on moving paper as an ergogram (Fig. 1 ) . A half-hour after a voluntary muscle ergogram has been obtained, the apparatus with the identical settings of finger, wrist, and arm positioning points is again connected to the patient. Then, the electrode from a Batrow muscle stimulator is placed over the motor point of the first dorsal interosseous muscle and the electronic3 ergogram produced as previously described. Figure 2 shows examples on the left, under A, of a normal ergogram obtained by an apparatus with a 10-oz. weight on the bar. The rested subject was able to perform this amount of work indefinitely; amplitude was even and sustained. On the right of A, the same muscle is being stimulated and is producing the electronic ergogram. When the electrode approximates 2 cm. in diameter over the motor point of the muscle, the amount of weight the normal muscle can pull is only 4 oz.; the muscle does not have more than 60% of the amplitude of the voluntary ergogram. This is because the electrical stimulation is limited to the area mentioned 2 cm. of muscle while, with voluntary use, the entire muscle and the adductor pollicis muscle are utilized. Therefore, with the voluntary ergogram versus the electronic ergogram of the same muscle, we have a ratio of \rolunt? of approximately 5 to 1. This ratio varies in some individuals according to skill in locating the motor point and may be 3 to 1, 2 to 1, or even 6 to 1. Using a 10-oz. weight, a patient with Parkinson’s disease tires easily (Fig. 2B, left). However, at the arrow, the patient is told to make a strong effort and immediately returns the ergogram to normal levels for 1 contraction only; the ergogram then falls back to greatly diminished value. When a patient with Parkinson’s disease uses a 4-oz. weight, repetition of the test an hour later shows little improvement. Again on urging the patient, the ergogram reaches toward normal values as indicated under the arrow. Figure 2B, left, represents 4 oz. In Figure 2C, the other arm of the same patient, as shown in B, is tested demonstrating the impairment with the 10-02. or the 4-02. Electronic