Electromyographic assessment of paratonia

Abstract

Many years after its initial description, paratonia remains a poorly understood concept. It is described as the inability to relax muscles during muscle tone assessment with the subject involuntary facilitating or opposing the examiner. Although related to cognitive impairment and frontal lobe function, the underlying mechanisms have not been clarified. Moreover, criteria to distinguish oppositional paratonia from parkinsonian rigidity or spasticity are not yet available.Paratonia is very frequently encountered in clinical practice and only semi-quantitative rating scales are available. The purpose of this study is to assess the feasibility of a quantitative measure of paratonia using surface electromyography. Paratonia was elicited by performing consecutive metronome-synchronized continuous and discontinuous elbow movements in a group of paratonic patients with cognitive impairment. Goniometric and electromyographic recordings were performed on biceps and triceps brachii muscles. Facilitatory (mitgehen) and oppositional (gegenhalten) paratonia could be recorded on both muscles. After normalization with voluntary maximal contraction, biceps showed higher paratonia than triceps. Facilitatory paratonia was higher than oppositional on the biceps. Movement repetition induced increased paratonic burst amplitude only when flexion and extension movements were performed continuously. Both facilitatory and oppositional paratonia increased with movement repetition. Only oppositional paratonia increased following faster movements. This is the first study providing a quantitative and objective characterization of paratonia using electromyography. Unlike parkinsonian rigidity, oppositional paratonia increases with velocity and with consecutive movement repetition. Like spasticity, oppositional paratonia is velocity-dependent, but different from spasticity, it increases during movement repetition instead of decreasing. A quantitative measure of paratonia could help better understanding its pathophysiology and could be used for research purposes on cognitive impairment.

Spasticity and spastic dystonia: the two faces of velocity-dependent hypertonia

“…The examiner randomly interposed a few metronome tones so that the interval between the beginning of two successive movements ranged from 3 to 10 seconds. This variable time interval prevented subjects from anticipating the subsequent displacement, thus minimizing paratonic muscle activity (Marinelli et al, 2017). To evaluate spastic dystonia changes during repetitive movements, s-EMG was also recorded in the 1000ms preceding each muscle stretch, with the patient in the starting position.…”

Paratonia in Dementia: A Systematic Review

“…One study [25] defined oppositional paratonia as "a form of hypertonia in late stage dementia". Two studies [11,43] stated that paratonia can be divided into two separate entities: "facilitory paratonia", in which the patient moves along with the examiner (keeping control of the movement, or inability to relax), and "oppositional paratonia", in which the subject appears to resist the passive movement of the examiner.…”

“…The PAI has only expert validity and face validity. In a three-stage study examining 87, 97, and 24 participants with an established form of dementia, interobserver reliability as measured by Cohen's kappa ranged from 0.63 to 1.Facilitory paratonia can be diagnosed with the paratonia scale, which establishes the subjective impressions of both assistance and resistance offered to passive flexion and extension about the elbow[11,43]. Facilitory paratonia can also be diagnosed with the modified Kral procedure as described by Beversdorf and Heilman[11].Marinelli et al [43] validated a quantitative method to assess and visualize facilitory and oppositional paratonia in elbow flexor and extensor muscles using surface electromyography (EMG) and metronome-controlled passive movements.…”

Ghost spasticity in multiple sclerosis

“…The latter finding did not surprise us as any experienced clinician knows that normal subjects may have difficulty relaxing their muscles during tone assessment. These healthy people are affected by oppositional paratonia (Dupré, 1910), a frequently encountered phenomenon not only in patients with cognitive impairment (Beversdorf and Heilman, 1998;Marinelli et al, 2017b), but also in healthy subjects (Damasceno et al, 2005;Manfredi, 1994). Tonic muscle stretch produced no EMG activity in the 17 healthy subjects who were fully relaxed at the clinical examination.…”