Have you ever seen someone look stiff and difficult to move? This may be caused by hypertonia, a muscle tone disorder that makes muscles too tense. Hypertonia is the opposite condition of hypotonia, a condition when muscle tone is very low, so that the body is very weak and difficult to move.
What is hypertonia?
Hypertonia is a state of excessive muscle tone, so that body parts such as arms or legs become stiff and difficult to move. Muscle tone is the amount of muscle tension needed for the body to support movement properly.
Hypertonia occurs when the areas of the brain or spinal cord that control the signals that regulate muscle tone and tell muscles to contract are damaged.
Hypertonia can limit joint movement so that people with this condition may have a stiff gait and fall easily because the body is difficult to react and maintain balance.
Severe hypertonia can cause the joints to become “frozen”, also known as joint contractures.
The term spasticity is also often used interchangeably with hypertonia. Spasticity is a type of hypertonia characterized by increased muscle contraction when moving. In this type, hypertonic patients may have exaggerated reflex responses.
Another type of hypertonia is rigidity or stiffness, in which the muscles have the same amount of stiffness regardless of the level of movement performed.
Causes of hypertonia in babies
Hypertonia in infants can be caused by a communication error in the central nervous system that regulates the interaction between nerves and muscles. Damage or disruption to the baby’s brain pathways causes the muscles not to listen to nerve signal commands, so if the muscle tone is too high, the brain can’t give commands to the nerves to let the muscles relax.
Causes of impaired pathways leading to the diagnosis of hypertonia include:
- Birth injuries such as lack of oxygen while moving through the birth canal
- Brain tumor
- Injury to the central nervous system
- Disorders of the formation of the brain when the baby is in the womb
- A variety of conditions that affect the way nerves communicate with muscles.
If your baby is diagnosed with hypertonia, the doctor may check for other conditions that could have hypertonia as a symptom, such as cerebral palsy, multiple sclerosis and Parkinson’s disease.