This chapter gives an overview and update on functional neurological disorder (FND), also known as dissociative neurological symptom disorder and previously known as conversion disorder. FND is the presence of neurological symptoms that are not explained or explainable by a neurological disorder. FND has been assumed to be a purely stress-related psychiatric disorder, but over the recent decades, this simplistic conception has been supplanted by more nuanced models of symptom generation. FND is no longer a diagnosis of exclusion. Instead, wherever possible, it is ruled-in by distinct features of history and examination, the latter known as positive clinical signs. There have been concurrent advances in the biological understanding of FND, exemplified by functional neuroimaging studies that have indicated that FND can be distinguished from, for example, feigned symptoms mimicking the disorder. FND encompasses multiple subtypes, from seizures to motor disorders to sensory abnormalities. Symptoms often co-occur, sometimes in a striking fashion.

Current treatment options for FND are limited, and many patients have severe long-term symptoms despite best-available treatment including psychological therapies and medication. Nevertheless, there are simple, and sometimes effective, steps that clinicians can take to manage and treat patients.

Psychiatric illness may be associated with objective or subjective motor disorders. This chapter is chie?y devoted to objective motor disorders, but subjective motor disorders may also occur. It is difficult to classify motor disorders because although clear-cut individual motor signs (such as stereotypies) can be treated as if they were neurological symptoms, it is much more difficult to classify more complicated patterns of behaviour. Nonetheless, motor disorders can be broadly grouped into the following categories: (a) disorders of adaptive movements; (b) disorders of non-adaptive movements; (c) motor speech disturbances; (d) disorders of posture; (e) abnormal complex patterns of behaviour; and (f) movement disorders associated with antipsychotic medication. This chapter explores and explains these different categories of motor disorder in the context of psychiatric illness. The chapter concludes with suggested questions for eliciting specific symptoms in clinical practice, in addition to standard history-taking, mental state examination and physical examination.