A device to evaluate motor and autonomic impairment

Various devices have been developed to assess impairment of the autonomic nervous system, while other devices have been developed to evaluate the motor system. However, no devices have been developed to examine the interaction between the autonomic and somatic nervous systems. Therefore, the device described here, a square platform which was 0.7x0.7 m in length and 0.1m thick, was developed to examine somatic-autonomic interaction. The device can be used by placing it directly on the floor or on 1 of 2 pivots; one that allowed the platform to move 0.2m (+/-44.1 degrees) in the front to back or side to side direction and one that allowed both movements together. Strain gauge load cells in the platform measured sway and tremor during the subjects attempt to balance and a continuous blood pressure monitor and the ECG were used to assess the response of the autonomic nervous system (heart rate variability). The device was tested on 5 normal subjects and the following was evaluated: (1) sway during standing, (2) weight shift during standing, (3) frequency of sway and extent of sway during standing, (4) sympathetic and parasympathetic alterations in the ANS during attempted balance, and (5) phase delays between motor and autonomic responses. The results showed that, with increasing balance challenge, sway increased, tremor increased, the sway angle increased and sway was positively correlated with heart rate and negatively correlated with blood pressure. A balance challenge significantly increased sympathetic activity but not parasympathetic activity. This device should have useful applications in assessing motor impairments and sensory and autonomic impairments in a variety of conditions.