Clinical, genetic and neurophysiological features of psychiatric and cognitive symptoms in cervical dystonia and the role of the superior colliculus

The adult-onset idiopathic focal dystonias (AOIFDs) are a group of hyperkinetic movement disorders. Cervical dystonia (CD) is the most common expression and shows motor (dystonic neck posturing) and non-motor (sensory, psychiatric and cognitive) features. Many aspects of the non-motor syndrome are unknown, as is the pathophysiology of CD. Pathophysiological explanations concentrate on the motor features, neglecting the significant burden of the non-motor syndrome. This thesis focuses on the non-motor syndrome- the influence of sex on CD, psychiatric changes and their longitudinal course, cognitive dysfunction with an emphasis on social cognition, the role of genetics on mood disorders and, electroencephalographic measures of social cognition. The primary aim was to highlight features of the non-motor syndrome of CD. The main findings of this thesis were as follows: 1-Patients with CD suffer from significant mood symptoms. These are an independent feature of the disease and can affect age at onset. These features don’t necessarily correlate with the severity of the motor syndrome. There are flaws with existing rating scales for mood assessment in CD. One simple and reliable method is the Dystonia Non-Motor Symptoms Questionnaire (DNMSQuest). 2-CD is known to be genetic and autosomal dominant in transmission. Patients report a high incidence of family history of mood disorder, higher than what would be expected from a community sample. This could indicate that mood symptoms are also genetically transmitted. 3-A number of cognitive changes are seen in CD, ranging from issues with executive function to memory and information processing. Social cognition, in particular, seems to be affected and may have a significant on quality of life. 4- Subclinical processing of facial expressions is aberrant in patients with CD measured by evoked response potentials (ERPs). This implicates the face recognition pathway in the pathophysiology of CD. This thesis also proposes an anatomical and functional framework that can explain the motor and non-motor syndrome of CD highlighting the importance of the superior colliculus.