Functional neurological disorder is common in patients attending chronic pain clinics

BACKGROUND: Chronic pain is a common comorbidity in those with functional neurological disorder (FND), however the prevalence and characteristics of FND in those with chronic pain is unknown.

METHODS: A retrospective electronic records review of consecutive new patients attending a chronic pain clinic of a regional service. Clinical features, medication and outcome of chronic pain, any lifetime diagnoses of functional, FND and psychiatric disorders and undiagnosed neurological symptoms were recorded.

RESULTS: Of 190 patients attending the chronic pain clinic, 32 (17%) had a lifetime diagnosis of FND and an additional 11 (6%) had undiagnosed neurological symptoms. Pain patients with comorbid FND were more likely to have chronic primary pain (88% with FND, 44% without FND, p < 0.0001), widespread chronic primary pain (53%, 15%, p < 0.00001) and depression (84%, 52%, p < 0.005) and less likely to have a pain-precipitating event (19% vs 56%, p < 0.001). However, there was no significant difference between these patients in opiate prescription, benzodiazepine prescription or pain outcome.

CONCLUSIONS: This first study of FND in a chronic pain patient population found a remarkably high prevalence of FND (17%) and is possibly an underestimate. The size of the overlap indicates that FND and chronic pain research fields are likely to have a lot to learn from each other.