Perspectives on functional and hyperkinetic movement disorders Phenomenology & pathophysiology

Functional movement disorders (FMD), previously known as conversion disorders or psychogenic movement disorders, are abnormal movements which cannot be attributed to other neurological disorders. FMD are frequently encountered in movement disorder outpatient clinics. Yet, most neurologists consider FMD difficult to diagnose. Clinically, the phenomenology of jerky movement disorders ranges from FMD to tics and myoclonus.
The main objective of this thesis is to elucidate the phenomenology and pathophysiology of jerky FMD from a clinical, electrophysiological and neuro-imaging perspective. The aim is to identify features that help to differentiate patients with FMD from patients with other hyperkinetic movement disorders, in particular myoclonus and tics.
The first chapters of the thesis entail several studies on the clinical phenomenology of FMD, tics and myoclonus. Next, we assess the diagnostic value of the Bereitschaftspotential (BP).
The BP is an early EEG potential preceding self-initiated movements. In clinical practice, presence and duration of a BP preceding a jerk of unknown aetiology is used to differentiate between myoclonus, FMD and tics.
In the following chapter of the thesis, a neurophilosophical perspective on the phenomenology of movement disorders is provided. We report the findings of the phenomenological study on FMD, measuring the perceived voluntariness of FMD, tics and myoclonus as perceived by clinicians and patients and explored the relationship of perceived voluntariness and the BP. The last chapter of the thesis aims to elucidate the pathophysiological mechanisms of FMD using neuro-imaging.