Amplitude and velocity dependence of patellar pendulum triggered by T reflex in Parkinson's rigidity

The relation between increase of tonus and joint movement velocity is controversial in Parkinson's rigidity. It is accepted that the increase of tonus in rigidity is constant during joint movement, and does not change within all limits of movement. However, there is thoughtful evidence that the change in tonus in rigidity has a correlation with joint movement velocity and amplitude of movement. The pendulum movement that is formed by triggering of the patellar T reflex allows the examination of phasic stretching reflexes and physiological changes of passive stretching. Therefore, the velocity and amplitude properties of tonus in Parkinson's rigidity can be scanned together.

Patellar T reflex-triggered patellar pendulum was recorded in 40 Parkinson's patients. The velocity and amplitude changes in the pendulum were observed according to the rigidity scale. Muscle action potentials were recorded from the rectus femoris muscle and biceps femoris muscles simultaneously via superficial recording electrodes. Knee joint angle changes were recorded with a goniometer. The kinesiological and electromyographic features were compared with those of the control subjects.

The number of pendulums decreased significantly, the angle of joint movement decreased, the peak time decreased and the angular velocity slowed down significantly in the Parkinson's group. While the latency of the patellar T reflex did not change significantly, its amplitude decreased, and the onset time of joint movement measured by accelerometer was prolonged.

Parkinson's rigidity has a velocity-dependent component, and this correlates negatively with the rigidity scale.