Predisposing Risk Factors for Functional Limb Weakness: A Case-Control Study

Objective: Functional limb weakness is a common symptom of functional neurological disorder. Few controlled studies have examined possible predisposing factors to determine their specificity for this symptom. Methods: In this prospective case-control study, patients with functional limb weakness (<2 years duration, N=107) were compared with a control group (comprising patients with weakness attributable to neurological disease, N=46, and healthy individuals, N=39). A structured clinical interview and questionnaires assessed potential predisposing factors, including family structure and childhood abuse and neglect (Childhood Trauma Questionnaire [CTQ]), personality traits (NEO Five-Factor Inventory), medical and surgical comorbidity, and exposure to a symptom model. Results: The patients with functional limb weakness and the control subjects were similar in gender and age. Self-reported childhood sexual abuse (15% versus 5%, p<0.01), and physical abuse (18% versus 7%, p<0.01: CTQ moderate or above) were more common in the functional limb weakness group, although the absolute frequency was lower than anticipated. In the functional limb weakness group, there were modest differences in two personality traits, compared with the control group: higher neuroticism (p=0.02) and lower openness (p=0.01). Medical comorbidity, including appendectomy (33% versus 5%), irritable bowel syndrome (36% versus 18%), and chronic back pain (40% versus 16%), was more frequent in the functional limb weakness group. There were no differences in birth order or exposure to a symptom model. Conclusions: Medical and surgical comorbidity and adverse childhood experience are risk factors, but not essential, for the development of functional limb weakness. However, evidence for personality traits or exposure to a symptom model is less robust.