paratonia

Paratonia is an age-related or disease-related abnormal increase or decrease in resistance to passive movement that is variable and influenced by the patient’s attention, effort, and emotional state. It is most often described in adults with dementia or other frontal brain disorders and is sometimes referred to as the gegenhalten phenomenon.

Clinical features include inconsistent resistance to passive limb movement that is not primarily velocity dependent, as seen with spasticity. The tone may appear stronger or weaker at different moments, and the response can shift with changes in arousal, distraction, or emotional state. The examiner may observe both opposing resistance and sudden “give” during a single passive movement, and the pattern can be bilateral.

Pathophysiology is not fully understood, but paratonia is thought to reflect dysfunction of frontal-subcortical circuits that normally regulate tone and motor inhibition. The resulting loss of inhibitory control over motor neurons leads to a variable, context-sensitive resistance to movement rather than a fixed spastic or rigid pattern.

Etiology and associations include neurodegenerative diseases, especially frontotemporal dementia and Alzheimer’s disease, as well as other acquired brain injuries, delirium, and diffuse cerebral involvement. It is a clinical sign rather than a separate disease entity and can complicate care and rehabilitation.

Diagnosis is clinical and based on observation during passive movement, noting the variable, non-velocity-dependent resistance and its fluctuation with attention or emotional state. Differential diagnosis includes spasticity, rigidity, dystonia, and catatonia; imaging or neurophysiology is typically used to evaluate the underlying disorder rather than to diagnose paratonia itself.

Management focuses on treating the underlying condition and reducing distress or agitation. Gentle handling, reassurance, consistent routines, and graded physical therapy are commonly used. Prognosis varies with the underlying disease and generally reflects the broader neurologic condition rather than paratonia alone.