Clinical neurophysiology of functional motor disorders: IFCN Handbook Chapter

Abstract

Functional Motor Disorders are common and disabling. Clinical diagnosis has moved from one of exclusion of other causes for symptoms to one where positive clinical features on history and examination are used to make a "rule in" diagnosis wherever possible. Clinical neurophysiological assessments have developed increasing importance in assisting with this positive diagnosis, not being used simply to demonstrate normal sensory-motor pathways, but instead to demonstrate specific abnormalities that help to positively diagnose these disorders. Here we provide a practical review of these techniques, their application, interpretation and pitfalls. We also highlight particular areas where such tests are currently lacking in sensitivity and specificity, for example in people with functional dystonia and functional tic-like movements.

Keywords: Clinical neurophysiology; Electrophysiology; Functional Movement Disorders; Functional Neurological Disorder.

Fig. 1

A) Segment of co-registered EEG (top) and EMG (bottom) traces. A jerk is visible as muscle bursts in the EMG traces; the corresponding EEG traces are affected by movement artifact. B) Jerk-locked back-averaging of many segments results in a visual representation of the association in time between cortical activity at the vertex (Cz) and the jerky movement (EMG). In this case, a Bereitschaftspotential is visible, characterised by a slowly rising negative deflection over the vertex within 2 s before movement onset. C) Visual representation of the negative deflection (in blue) over the vertex 400 ms before movement onset. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)