Spasticity, Dystonia, High Tone, Low Tone and more, are hot topics that are talked about with gross motor development, and often when a child may be diagnosed with Cerebral Palsy from HIE. We worked with Medical Advisory Board member, Ed Hurvitz, MD, pediatric physiatrist from the University of Michigan to help our families understand a bit more about each term.
Muscle tone refers to the baseline tension in your muscles, which is set by different factors in your nervous system. It is measured by assessing the amount of resistance present in a muscle when it is moved through the range of motion. This assessment can be complicated by a contracture in the muscle, which is caused by shortening of the muscle, damage to the joint, or other non-neurologic factors.
There are a few different kinds of "hypertonia" or high tone.
SPASTICITY: The most common is spasticity, which is diagnosed when more resistance is noted in the muscle with faster movement of the joint. There is generally also a 'catch,' and then release which allows more movement. Spasticity is seen when there is damage to the brain and/or spinal cord of the type seen in many common syndromes such as cerebral palsy, stroke, spinal cord injury, and more.
DYSTONIA: Dystonia is described as causing twisting movements and twisted postures of the body. These are most commonly in the limbs but can be in the head and trunk as well. Dystonia can be a genetic condition, or it can be part of the high tone seen in other conditions like cerebral palsy or brain injury. Dystonia fluctuates, and at times may not be present. Spasticity is always present while awake.
RIGIDITY: Rigidity is often seen in Parkinson's disease or in severe brain injury. With rigidity, it is difficult to move the muscles through the range of motion, regardless of the speed with which the limb is moved. These types of hypertonia have different treatment options, so it is important to work with a physician who understands the diagnosis and treatments, such as a physiatrist (also known as a Physical Medicine and Rehabilitation doctor, or PMR).
There is also a type of tone called "hypotonia" or low tone.
Hypotonia is when there is low muscle tone, leaving muscles too relaxed. This can occur in brain injuries, such as HIE.
Children with cerebral palsy may have mixed tone, and a combination of different types of hypertonia, such as spasticity and dystonia.
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