RIGIDITY
Rigidity is generally associated with severity of involvement. The child with rigidity is characterized by simultaneous and continuous contraction of both extensors and flexors, with greater power being exerted by the extensors, resulting in a general lack of movement as opposed to inappropriate or involuntary movement. The limbs of the child with rigidity are virtually locked in full or over-extension, resulting in an arched position with the back stiff and head and feet at the extremes of the arch. The child with rigidity such that permits some controlled movement of an extremity has the further complication of involuntary movement of the opposite extremity (movement of the right arm results in a similar movement of the left).
Various associated complications are generally seen with these children ranging from severe respiratory problems to diminished vision and hearing, as well as seizure disorder