Hypertonia is a term sometimes used synonymously with spasticity and rigidity in the literature surrounding damage to the central nervous system, namely upper motor neuron lesions.

[1] Impaired ability of damaged motor neurons to regulate descending pathways gives rise to disordered spinal reflexes, increased excitability of muscle spindles, and decreased synaptic inhibition.

[6] Hypertonia is caused by upper motor neuron lesions which may result from injury, disease, or conditions that involve damage to the central nervous system.

Different patterns of muscle weakness or hyperactivity can occur based on the location of the lesion, causing a multitude of neurological symptoms, including spasticity, rigidity, or dystonia.

Rigidity is a severe state of hypertonia where muscle resistance occurs throughout the entire range of motion of the affected joint independent of velocity.

[12] 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.

[11] Isokinetic,[13][14][15][16] aerobic,[17][18][19] and strength training[20][21][22][23] exercises should be performed as prescribed by a physiotherapist, and stressful situations that may cause increased tone should be minimized or avoided.

Baclofen is generally the drug of choice for spinal cord types of spasticity, while sodium dantrolene is the only agent which acts directly on muscle tissue.