Functional cervical dystonia: diagnostic accuracy of distinct clinical features

Functional dystonia (FD) is one of the most common presentations among patients with functional movement disorders (FMDs). However, FD affecting neck muscles has not been well studied, even though cervical dystonia (CD) is one of the most common movement disorders.

We aimed to assess the clinical features and correlations of functional CD. Additionally, we compared the clinical features with 120 consecutive patients with non-functional CD and determined the diagnostic accuracy of contrasting variables.

We studied 72 consecutive patients with FD (n = 57, 79.2% were females), of whom 34 (47.2%) were identified with functional CD. The latter group had greater severity of FMDs determined by the Simplified Functional Movement Disorders Rating Scale (S-FMDRS) and a more common functional speech disorder compared with patients with FD without CD (P ≤ 0.001, for both variables). Compared to patients with non-functional CD, those with functional CD were younger, had more common retrocollis, anterior head shift, greater severity of dystonic postures, more frequent changing pattern of dystonia, more common dystonia in other body parts, lack of typical alleviating maneuvers (AM) and less frequent neck pain (P < 0.05, for all comparisons). Lack of AM had the highest sensitivity (0.97) and change in dystonia pattern had the highest specificity for the diagnosis of functional CD (0.98).

Functional CD represented 47.2% of patients with FD. Greater severity of FMDs and comorbid functional speech disorders were more common in patients with functional CD. Several clinical features distinguished functional to non-functional CD.