In classic spastic hypertonia, when a joint is moved passively, maximum resistance is felt after a few degrees. The more rapid the movement, the quicker and more pronounced the resistance. This classic form of spastic hypertonia is referred to as clasp-knife. In the most severe form of spastic hypertonia, the affected part will be rigid whether flexed or extended.
The symptoms associated with the spastic form of Cerebral Palsy lessen during sleep and are exacerbated by stress or voluntary movement.
