MRI Voxel-Based Morphology Provides Clues into Early Parkinson's Disease

Utilizing sophisticated magnetic resonance imaging (MRI), researchers are performing one of the first large-scale analyses of the extent of global (overall), tissue-specific, regional brain atrophy, and white matter hyperintensities (WMH) of early Parkinson's disease patients. WMH are diseased areas of the white matter seen typically in brain MRI scans in the elderly.

Parkinson's disease is a degenerative disorder of the brain affecting speech, movement, mood, behavior, thinking, and sensation for which there is no known cause or cure. Two studies from the University at Buffalo (UB; NY, USA) presented at the American Academy of Neurology meeting in Chicago, IL, USA, in April 2008 provided new insights into very early development of the disease.

The research is the result of a joint project by neurology and imaging specialists from UB, and from Norway's Stavanger University Hospital, and the University of Bergen. Turi O. Dalaker, M.D., a doctoral fellow from Stavanger University Hospital who conducted the research in the Buffalo Neuroimaging Analysis Center (BNAC), is first author on both studies.

The symptoms of Parkinson's disease (PD) result from disintegration of the brain's white matter, the network of nerves that transport messages to the various brain regions, and gray matter, the brain regions where those messages are received, interpreted, and upon which are acted.

Using advanced MRI technologies available at BNAC, the researchers can identify brain regions linked to PD based on images showing the status of both white and gray matter. One study, a case-control investigation, compared brain MRI scans and scores on the Mini-Mental State Examination (MMSE), a standard mental screening test, of 155 patients diagnosed with early Parkinson's disease with those of 101 normal subjects.

The study's findings showed that in PD patients, white matter hyperintensities were associated considerably with lower scores on the mental test: The more areas of hyperintensity, the lower the MMSE score. "The relationship between higher white matter hyperintensities and lower MMSE scores in PD provide a possible explanation for cognitive impairment in PD,” said Dr. Dalaker.

The second study examined whether mild cognitive impairment in early PD is associated with atrophy of a specific brain region. The researchers were interested also in investigating the possible link between mild cognitive impairment in PD and a higher risk of developing dementia.

Applying an MRI analytic process called voxel-based morphology, Dr. Dalaker and colleagues analyzed high-resolution MRI scans of 43 newly diagnosed PD patients and those of 31 sex-matched normal controls. The researchers discovered that the PD patients with mild cognitive impairment showed a trend toward reduced gray matter in the cingulate area, a brain region associated with cognitive performance. "This study shows that cingulate atrophy is associated with early cognitive deficit in PD,” said Dr. Dalaker, "and might serve as a possible biomarker for increased risk of developing dementia in PD.”

The subjects in both studies were part of The Norwegian ParkWest project, a four-center prospective longitudinal cohort study of patients with PD from southwestern Norway. The project involves 265 patients with early stage incident PD, their caregivers, and a control group of 205 participants with similar age- and sex- distribution. The researchers plan to follow this sample for 10 years.


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