Paratonia is the inability to relax muscles during muscle tone assessment. There are two types of paratonia: oppositional and facilitatory. Oppositional paratonia ("gegenhalten") occurs when subjects involuntary resist to passive movements, while facilitatory paratonia ("mitgehen") occurs when subjects involuntary assist passive movements.

Both types of paratonia have been associated with cognitive impairment or mental disorders, particularly in relation to frontal lobe dysfunction. Paratonia is frequently encountered in clinical practice.

Paratonia can be assessed with rating scales during clinical examination. Paratonia scale is a semi-quantitative score to rate the amount of oppositional and facilitatory paratonia separately. Kral modified procedure is a more objective semi-quantitative rating of upper limb facilitatory paratonia easily applicable while patients are seated. The Paratonia Assessment Instrument (PAI) was also used in a physiotherapic setting for the assessment of oppositional paratonia.

In 2017 facilitatory and oppositional paratonia have been assessed with surface electromyography, allowing a quantitative measure and better characterization of paratonia. Recording paratonia with electromyography on elbow flexor and extensors during repetitive continuous or discontinuous elbow movements may help distinguish paratonia from other forms of altered muscle tone. Both facilitatory and oppositional paratonia increase during continuous flexion and extension movements, moreover, oppositional paratonia increases with movement velocity. Spasticity also is velocity-dependent, but, differently from oppositional paratonia, if repeatedly elicited decreases instead of increasing. Conversely, parkinsonian rigidity is independent from movement velocity and probably also from movement repetition.

Treatment consists of high-dose lorazepam or in some cases ECT. The response to the treatment is usually good, especially if detected early

In the 19th century the psychiatrist Karl Ludwig Kahlbaum observed several symptoms of the disorder. Among them were stupor, mutism, excitement, hyperactivity, posing, negativism, rigidity, waxy flexibility and automatic obedience, stereotypies, tics, grimacing, echo-phenomenon, and self-harming.

Also marbling of the skin, profuse sweating, deviation of the pupils and odd reaction to light were considered catatonic phenomenons.

During most of the 20th century catatonia was regarded as schizophrenic in its nature, but towards the end of the century it was more commonly observed in those with bipolar disorder and autism spectrum disorder. Now only 15 percent of those with catatonia are considered to have schizophrenia.