An observational neuroimaging and neurophysiological study investigating the visual pathway in Huntington*s disease.

Huntington*s disease (HD) is a rare autosomal dominant inherited progressive
neurodegenerative disorder. Besides the well-known triad of clinical signs such
as motor disturbances, cognitive dysfunction and psychiatric symptoms, are
impairments of the visual system also frequently described in HD patients.
These impairments include visuomotor and visuospatial dysfunctions, impaired
visual attention, and deficits in naming visual objects.
Neuropathological studies demonstrated evidence of specific neuronal loss in
the visual system, which is consistent with structural neuroimaging studies
that show extensive thinning and atrophy of the visual cortex in different
disease stages. Also, neurophysiological investigation of the visual pathway
using visual-evoked potentials (VEP) showed reduced amplitudes and normal
latencies in manifest HD compared to controls suggesting involvement of the
visual cortex when the disease progresses.
Still, the visual pathway in the human brain has not yet been investigated
systematically in patients with HD. This explorative observational study will
therefore combine different neuroimaging modalities with neurophysiological
visual evoked potentials to improve our understanding about the
pathophysiological degenerative processes in HD.In addition, we want to
investigate if there is a correlation with clinical cognitive assessments
involving a visual component.

Primary objectives:
* To improve the understanding of alterations in the visual pathway in patients
with HD in different disease stages.
* To investigate possible changes in brain function and structure in rest and
in response to visual stimulation in patients with HD and healthy controls.
* To explore if visual cognitive impairments are related to changes in brain
structure and brain function in premanifest and manifest HD.

Secondary objectives:
* To examine occipital cortical function in premanifest and manifest HD using
visual-evoked potentials.
* To evaluate if there is a correlation between outcome measures of
neurophysiological and neuroimaging techniques.

This is a prospective, cross-sectional, observational explorative study in
Huntington's disease and healthy individuals that are not at risk for HD.

Participants will undergo different clinical and neuropsychological assessments
during a single visits of approximately 3 hours. These assessments will examine
the general physical and cognitive functioning.
Furthermore, each participant will undergo a MRI-scan of the brain and a
neurophysiological test (VEP). Both assessments are non-invasive and are also
commonly used in the daily clinical practice for general clinical care.
Therefore, there is no immediate risk associated with participation in this
study. Participants receive no immediate benefit from participation in this
study. The only potential benefit is a better understanding of the
pathophysiology of HD. The information obtained in this study may potentially
benefit the development of new treatments and help to plan future studies.