Movement perception of the tonic vibration reflex is abnormal in functional limb weakness

INTRODUCTION

We tested the hypothesis that functional limb weakness is associated with possible dysfunction of the central processing of proprioceptive information, by evaluating the amount of tonic vibration reflex (TVR) and the perception of the TVR movement.

METHODS

The study sample was 20 patients with functional weakness of the lower and/or the upper limbs and 25 healthy controls; delivery of 92-Hz transcutaneous vibration of the biceps brachii tendon of the unrestrained arm stimulated predominantly the muscle spindle afferent and elicited elbow flexion (tonic vibration reflex, TVR). Blindfolded participants had to match the final position of the vibrated arm with their contralateral tracking arm. The TVR and perception of the TVR movement were measured as angle movements of the vibrated arm and the tracking arm, respectively.

RESULTS

The magnitude of the TVR of the vibrated arm and movement perception of the TVR of the tracking arm were significantly reduced in the patients compared to the controls. No correlation was found between magnitude of the TVR and perception of the TVR movement, suggesting that the abnormalities were independent of each other. Moreover, the abnormalities did not differ between the patients with/without bilateral upper limb involvement or between the affected and the unaffected side in patients with unilateral impairment, suggesting that the observed deficits are independent of motor impairment.

CONCLUSIONS

Proprioceptive dysfunction may underlie alterations in body movement and in sense of agency in such patients and may play a role in the pathophysiology of functional limb weakness.

The Impact of Depression, Anxiety and Personality Disorders on the Outcome of Patients with Functional Limb Weakness - Individual Patient Data Meta-Analysis

OBJECTIVE

Psychiatric comorbidities such as depression, anxiety, and personality disorders are common in patients with functional limb weakness/paresis (FND-par). The impact of these conditions on the prognosis of FND-par has not been systematically reviewed. The aim of this study was to identify a potential prognostic effect of comorbid depression, anxiety, and/or personality disorder on prognosis in patients with FND-par.

METHODS

A systematic review was performed to identify studies that reported measures of baseline depression, anxiety, and/or personality disorder, and physical disability. An individual patient data meta-analysis was subsequently performed.

RESULTS

Eight studies comprising 348 individuals were included (7 prospective cohorts; 1 case-control study). There was heterogeneity in sample size, follow-up duration, and treatment modality. Depression and anxiety were present in 51.4% and 53.0% of FND-par patients, respectively. In individuals whose FND-par improved, there was no significant difference between those with versus without depression (52.6% vs 47.4%, p = 0.69) or those with versus without anxiety (50.3% vs 49.7%, p = 0.38). Meta-analysis showed no clear impact of baseline depression or anxiety per se [pooled OR for depression 0.85 (95%CI 0.50-1.45; p = 0.40) and anxiety 0.84 (95%CI 0.51-1.38; p = 0.91)]; and of depression or anxiety severity [pooled OR for depression 1.23 (95%CI 0.63-2.39; p = 0.91) and anxiety 1.40 (95%CI 0.70-2.78; p = 0.58)] on FND-par outcome. Insufficient data were available to assess the impact of personality disorders.

CONCLUSION

We found no evidence that depression or anxiety influenced outcome in FND-par. Large-scale, prospective studies in FND-par, and other FND subtypes, are needed to fully contextualize the impact of concurrent mental health concerns on outcomes.