P-2-06-07
POSTURAL LONG LATENCY RESPONSE IN PATIENTS WITH PARKINSON'S DISEASE AND SPINOCEREBELLAR DEGENERATION
Akira Yamaguchi, Hajime Hino, Itaru Onuki, Youko Dekura, Akiteru Takagi*: National Center Hospital for Mental, Nervous and Muscular Disorders. Tokyo, Japan. *University of Hiroshima. Hiroshima, Japan.
[Purpose] Long latency responses are thought to be important in Postural control. We studied the long latency components in leg muscles of patients with Parkinson's disease and Spinocerebellar degeneration (SCD).
[Subjects and methods] Subjects included 10 Parkinson patients (P-D), 6 SCD patients and 10 age-matched healthy volunteers. Surface EMG recording were obtained from four muscles in the right side leg (tibialis anterior (TA), medial gastrocnemius (MG), vastus lateralis (VL) and Hamstrings (H)). In subjects free standing on a movable platform (NeuroCom and Anima), sudden toes-up tilt (random 4°, 8°and predictable 4°,8°at velocity of 45 °or 25°/sec).
[Results] l) The latencies of the Long latency responses (LLR) in the TA didn't delay in the P-D subjects compared to the older control group. But, we found significant delay in the peak time of the center of gravity (COG) of P-D subjects (632±92.6 msec) compared to the control group (513.3±63.9 msec P<0.05), and the tendency to decrease in the LLR amplitude of P-D patients. 2) Comparison of the SCD patient's LL responses between the control group showed that LLR latency was significantly increased in the SCD patients (238.6±48.9) compared to the controls (183.1±29.5, P<0.01).
[Conclusion] This result suggest that LLR (TA and VL) is important for postural control in the sudden toes-up tilt. LLR showed the disorder of postural balance in the P-D and SCD subjects.
P-2-06-08
CHARACTERISTICS OF THE MUSCLE STIFFNESS OF FOREARM DURING A VISUAL-GUIDED TRACKING IN NORMAL AND ATAXlC PATIENTS
Ryoichi Hayashi, Norio Tahara*, Shoji Miki* (Department of Medicine (Neurology), Shinshu University School of Medicine, Matsumoto. *Department of Electrical and electronic engineering, Shinshu University, Nagano, Japan)
To investigate characteristics of visco-elasticity of the human muscle, we recorded EMG responses of the forearm muscles, a hand position and force when the subjects tracked a target (displayed on a CRT and moved 30 degrees at a constant speed of 10 deg/sec) by flexing the hand 30 degrees around the wrist joint against a constant elastic load, 0, 0.7, 1.4 or 2.1 Nm/30 deg. Eight patients with spinocerebellar degeneration (SCD) and 10 age-matched normal subjects were studied. The tracking error in SCD was larger than that in normal controls (p<0.05). The muscle activity of flexor muscles increased according to the increase of load in both groups. An FFT analysis of hand position showed two peaks; the first peak corresponded to tracking and the second peak shifted from 4 Hz to 6 Hz when the load increased in normal subjects. In patients, the second peak fluctuated more than that in normal subjects and appeared at a lower frequency, from 3 Hz to 6 Hz. During tracking in normal subjects, the muscle stiffness (△k=△torque/△hand position) increased linearly and it reached the value of the mechanical stiffness caused by the torque motor within 800 ms from the movement-onset and then it oscillated between 4 Hz to 6 HZ. In patients with SCD, the increase of △k within 800 ms was smaller and the following oscillations was lower than that of normal controls. These results suggest that a disturbance of appropriate adjustment of muscle stiffness for external elastic-load could cause augmentations of the tracking error and ataxic movement in SCD.
