Children with motor handicaps frequently have abnormal muscle tone, which may limit their abilities to achieve developmental motor milestones. Muscle tone refers to the resistance of a body part to passive movement and is thought of as muscle tension.
There are three basic types of abnormal muscle tone that may affect a child with a motor handicap: high tone or hypertonia, low tone or hypotonic and fluctuating tone (fluctuating from low to high or high to low)
Hypertonia: Increased tightness of muscle tone and reduced capacity of the muscle to stretch caused by damage to the motor nerve pathways in the central nervous system. Untreated hypertonia can lead to loss of function and deformity. Treatment can include physical and/or occupational therapy or medications. Injections of botulism toxin (Botox) are sometimes used in the treatment for chronic hypertonia in cerebral palsy and other disorders. It is also known as spasticity.
Hypotonia: Decreased muscle tone and strength that results in floppiness. Hypotonia is a common finding with cerebral palsy and other neuromuscular disorders. Untreated hypotonia can lead to hip dislocation and other problems. Treatment is via physical therapy. In some cases, braces may be needed to permit a full range of movement in patients with hypotonia.
Some children show variations in tone, ranging from hypotonia to hypertonia or vice versa. Tone may change in different body parts depending upon the child’s position or the activity in which she is involved. The most common type of motor handicap in which fluctuating muscle tone occurs is athetoid cerebral palsy.
The child with athetoid cerebral palsy has wide ranging, somewhat uncontrolled movements of the arms, legs, and face. Her tone will vary depending upon the position of her body or the difficulty of the task that she is trying to complete. These children, like children with hypotonia, may also appear to be “double_ jointed “and are at risk for joint dislocations and subluxations (partial dislocations).