| Hypertonia | |
|---|---|
| Classification and external resources | |
| ICD-10 | P94.1 |
| ICD-9 | 358, 779.89 |
| DiseasesDB | 20872 |
| MeSH | D009122 |
Hypertonia a condition marked by an abnormal increase in muscle tension and a reduced ability of a muscle to stretch. It is caused by lesions to upper motor neurons[1] in the central nervous system, which carry information from the central nervous system to the muscles and control posture, muscle tone, and reflexes. When the injury occurs in children under the age of 2, the term cerebral palsy is often used.[2] Damage to the central nervous system results in the loss of control of motor neurons and gives rise to disordered spinal reflexes, increased excitability of muscle spindles and decreased synaptic inhibition[3]
Hypertonia may result from injury, disease, or conditions that involve damage to the central nervous system. Examples include spasticity, dystonia (prolonged muscle contractions that cause twisting and repetitive movements or abnormal posture) and rigidity.
Rigidity is a state of hypertonia where muscle resistance occurs throughout the entire range of motion and is independent of velocity (whereas spasticity is velocity-dependent). It is frequently associated with lesions of the basal ganglia. People with rigidity present with stiffness, decreased functional ability and flexibility. There are two main forms of rigidity: leadpipe and cogwheel. With leadpipe rigidity, resistance from the muscle(s) remains throughout the entire range of movement and it is not velocity-dependent.[3] When rigidity is present with Parkinson's disease it is often termed as cogwheel. Cogwheel rigidity is a hypertonic state with rachetlike movements, and is believed to be present when rigidity and tremor occur together. Furthermore, the muscle(s) that have rigidity will not return to a fixed position after taken through range of motion[4]
Spastic hypertonia involves uncontrollable muscle spasms, stiffening or straightening out of muscles, shock-like contractions of all or part of a group of muscles, and abnormal muscle tone. It is seen in disorders such as cerebral palsy, stroke, and spinal cord injury. A form of hypertonia unrelated to spasticity is known as Paratonia, which is associated with dementia.
Dystonic hypertonia refers to muscle resistance to passive stretching (in which a therapist gently stretches the inactive contracted muscle to a comfortable length at very low speeds of movement) and a tendency of a limb to return to a fixed involuntary (and sometimes abnormal) posture following movement. It is seen is the different forms of dystonia and sometimes in parkinsonism.
Rigidity is an involuntary stiffening or straightening out of muscles, accompanied by abnormally increased muscle tone and the reduced ability of a muscle to stretch. This type of hypertonia is most common in parkinsonism.
Hypertonia can be so severe that joint movement is not possible. Untreated hypertonia can lead to loss of function and deformity.[2]
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Physiotherapy has been shown to be effective in controlling hypertonia with the use of static stretching which reduces motoneuron excitability.[5] Other interventions include icing, inhibitory pressure (applying firm pressure over muscle tendon), promoting body heat retention, and rhythmic rotation (slow repeated rotation of affected body part to stimulate relaxation).[6] A more unconventional method for limiting tone is to deploy quick repeated passive movements to an involved joint in cyclical fashion; this has also been demonstrated to show results on persons without physical disabilities.[5] For a more permanent state of improvement, exercise and patient education is imperative.[6] Isokinetic,[7][8][9][10] aerobic,[11][12][13] and strength training[14][15][16][17] exercises should be performed as prescribed by a physiotherapist, and stressful situations that may cause increased tone should be minimized or avoided.[6]
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