Objective: Aim of the present study was to assess the sensory-discriminative and cognitive-emotional aspects of pain in patients with functional and idiopathic dystonia respectively assessing pain threshold and pain tolerance in affected and unaffected limbs.

Background: Pain is often experienced by patients with functional dystonia and might occur also in body segments not affected by involuntary movements. We hypothesized an alteration of cognitive-emotional component of pain in patients with functional dystonia.

Methods: We enrolled 10 patients with idiopathic cervical dystonia (CD), 10 patients with functional dystonia (F-dys) and 15 age and gender matched healthy controls (HC). All patients with F-Dys had symptoms restricted to one body side, except for 2 patients with predominant right side involvment. Exclusion criteria were presence of cognitive impairment according to MMSE≤24, presence of lesions in peripheral and central sensory pathways , diagnosis of diabetes. Each patient underwent clinical evaluation by means of the Burke-Fahn-Marsden Rating Scale (BFMRS), the pain score of the TWTRS, Hamilton’s depression and anxiety rating scales (HDRS, HARS). We assessed tactile threshold, pain threshold (P-Th) (intensity at which sensation changed from unpainful to faintly painful) and pain tolerance (P-Tol) (intensity at which painful sensation was intolerable) by delivering electrical pulses of increasing intensity to the index finger of each hand.

Results: No difference was found between groups for tactile threshold for both hands. P-Th was significantly increased only in the affected hand of patients with F-Dys compared to CD (p=0.04). P-Tol was significantly increased in both the affected (p = 0.03) and unaffected (p=0.04) hand of F-Dys compared to CD. No difference was found between idiopathic CD and HC in pain thresholds, regardless of the presence of pain in CD. Spearman Rank Correlation did not demonstrate any correlation between P-Th or P-Tol with pain score, HDRS, HARS, BFMRS (movement and disability scores), disease duration, age at onset.

Conclusions: Patients with functional dystonia have an impairment of the sensory-discriminative component of pain in the affected hand and of the cognitive-emotional component of pain in both hands, regardless of the presence of abnormal movements. We hypothesize that the abnormal connectivity between the motor and the limbic system might account for abnormal pain processing in functional dystonia.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/impaired-pain-processing-in-functional-dystonia/