A practical review of functional neurological disorder (FND) for the general physician

Abstract

We present a practical overview of functional neurological disorder (FND), its epidemiology, assessment and diagnosis, diagnostic pitfalls, treatment, aetiology and mechanism. We present an update on functional limb weakness, tremor, dystonia and other abnormal movements, dissociative seizures, functional cognitive symptoms and urinary retention, and 'scan-negative' cauda equina syndrome. The diagnosis of FND should rest on clear positive evidence, typically from a combination of physical signs on examination or the nature of seizures. In treatment of FND, clear communication of the diagnosis and the involvement of the multidisciplinary team is beneficial. We recommend that patients with FND are referred to specialists with expertise in neurological diagnosis. FND is a common presentation in emergency and acute medical settings and there are many practical elements to making a positive diagnosis and communication which are useful for all physicians to be familiar with.

Keywords: conversion disorder; dissociative seizures,; functional neurological disorder; treatment.

Fig 1.

Hoover's sign. Hoover's sign is positive if there is weakness of hip extension (left) which returns to normal with contralateral hip flexion against resistance (right). The hip abductor sign is similar test showing discrepancy between voluntary and automatic hip abduction strength.

Fig 2.

Functional dystonia. Functional dystonia usually presents with a fixed posture with ankle inversion (a), or flexion of fingers (b) or wrist. In the face, look for jaw deviation, contraction of platysma or orbicularis and sometimes tongue deviation (c).