Treatment with a position feedback-controlled head stabilizer

A position feedback-controlled head stabilizer has been developed to provide cerebral palsied individuals with resistive exercise to strengthen the neck musculature. This apparatus detects "involuntary" head motion and stabilizes the head by applying opposing forces; it also can be used to facilitate muscular contraction by resisting the subject's voluntary movements. The purpose of the present study was to determine whether voluntary head control in cerebral palsied individuals can be improved through systematic exercise using the stabilizer to strengthen the muscles of the neck and improve their balance of action. The findings support the author's contention that this is possible. The apparatus consists of a helmet and shoulder pads, interconnected so that the head is supported in the helmet by a manipulator arm. At its lower end, the manipulator arm is attached to the shoulder pad mounting frame via a gimbal assembly which allows head movement in two planes of tilt (pitch, or forward-and back, and roll, or side-to-side). Feedback control circuitry is so arranged that any deviation of the head from the desired position leads to actuation of pneumatic cylinders, which apply torques to the manipulator gimbal axes so as to oppose or conteract the incipient head movement. It is particularly significant that none of these patients participating in these experiments were at all apprehensive about or resisted being placed in the apparatus. (Even the youngest subject to use the apparatus--five year old-- did not mind being restrained by the shoulder pads or having his head gripped by helment.) While JG utilized the safety release valve quite often during the first few head control training sessions, he soon became confident enough in the action of the stabilizer that he did not even bother to grip the handle of the release valve. While DA had the action of safety valve explained and demonstrated for her, she never bothered to use it even from the outset of her experience with the stabilizer. Thus, it seems that the football shoulder pads use to stabilize the shoulders and the hockey helmet used to grip and manipulate the head actually make the apparatus attractive to younger patients, while the padding thereby provided makes it comfortable enough to be tolerated well by older individuals. And, the subject's knowing that he has an override control by means of which he can assert command over the entire system appears to be of psychological benefit in establishing confidence in both the apparatus and the investigator.