Correlation of Positive Signs of Functional Neurological Disorder With Headache Severity: A Prospective Cross-Sectional Study.

Objective
Positive signs are clinical signs that are not explained by a structural neurological lesion and are considered the hallmark of functional neurological disorder (FND). In the literature and in clinical experience, positive signs are observed among patients without FND. The aim of the study was to examine the significance of positive signs among headache patients.
Methods
The authors of this prospective study recruited patients in headache consultation at the University Hospital Inselspital, Bern, Switzerland. Inclusion criteria were headache or facial pain in the past 3 months and age ≥18 years. The exclusion criterion was a known diagnosis of FND. All patients were examined for 14 validated positive signs: give-way weakness, co-contraction, sternocleidomastoid sign, trapezius elevation test, head flexion test, drift without pronation, Hoover I and II, spinal injury test, arm drop test, lip-pulling sign, midline splitting, splitting of vibration sign at the front, and expressive behavior sign.
Results
In total, 101 patients were recruited (69% female; mean±SD age=40.8±16.3 years), of whom 43% showed positive signs. Splitting of vibration was the most common sign (27%); the other signs were less frequent (≤10%). Patients with positive signs were older than patients without such signs and had more monthly headache days and exacerbations as well as more intense headache at examination. Multivariable logistic regression revealed a significant association between positive signs and exacerbation days per month (OR=1.08, 95% CI=1.01-1.14, per exacerbation day; p=0.019).
Conclusions
Positive signs are frequent among headache patients and point toward a more severe headache condition. This finding suggests overlapping mechanisms in headache and FND.