Introduction
Upper limb tremor is a debilitating symptom of chronic inflammatory demyelinating polyneuropathy (CIDP). It generally does not respond well to therapy, and its pathophysiology is debated. Both a peripheral and central cause of tremor in CIDP have been hypothesized, and also an interplay between the two has been proposed. In case a central pathophysiology underlies tremor in CIDP patients, the cerebello-thalamo-cortical circuit may be involved. This has not been researched in CIDP before, but this circuit is known to play a role in other tremor disorders. Functional Magnetic Resonance Imaging (fMRI) can non-invasively assess brain activity, and will be used in this thesis to investigate a potential central pathophysiology of tremor in CIDP patients.

Aim
The aim of this thesis is to assess brain activity in the cerebello-thalamo-cortical circuit in CIDP patients who suffer from tremor, and compare this to the brain activity in this circuit in CIDP patients without tremor.

Methods
fMRI scans were acquired from both CIDP patients who suffered from tremor (tremor group), and CIDP patients without tremor (control group). All participants performed two motor tasks, alternated with rest. In the static motor task, they extended their arms in front of them, inducing a postural tremor in the patients from the tremor group. In the dynamic motor task, all participants extended their arms and additionally performed a tremorlike movement with their hands. In the tremor group, an intentional tremor cooccurred with the voluntary movement of the dynamic motor task. A general linear model was used to analyse the fMRI data. Within-group and between-group analyses of clusters of brain activity were performed using one-sample and two-sample t-tests respectively.

Results
9 tremulous CIDP patients and 12 controls were included in the analysis. In the between-group analysis of the static task, more activity in CIDP patients with tremor in comparison to CIDP patients without tremor was found in lobule VIII of the cerebellum, the premotor cortex and supplementary motor areas, the visual cortex, and the fusiform. In the dynamic task, CIDP patients with tremor showed more activity in lobules IV/V of the cerebellum, the premotor cortex and supplementary motor areas, the supramarginal gyrus, the pars orbitalis, the insula, and the Rolandic operculum.

Conclusion
The results suggest that there is more brain activity in the cerebello-thalamo-cortical circuit in CIDP patients who suffer from tremor in comparison to CIDP patients without tremor. However, the results of the dynamic task may be influenced by a difference in brain activity due to the voluntary tremorlike movement. Further research is necessary to first of all separate the brain activity related to tremor from activity resulting from the voluntary movement, and furthermore to give insight into if this hyperactivity in the cerebello-thalamo-cortical circuit in CIDP patients with tremor is the cause of tremor, maintaining it, or is a reflection of the tremor.