MRI studies provide new insight on early Parkinson's disease

Parkinson's disease is a degenerative disorder of the brain affecting movement, speech, mood, behaviour, thinking and sensation for which there is no known cause or cure.

Two studies from the University at Buffalo being presented at the 2008 American Academy of Neurology meeting in Chicago shed new light on very early development of the disease.

The work is the result of a joint project by neurology and imaging specialists from UB, Stavanger University Hospital and University of Bergen, both in Norway.

Turi O. Dalaker, M.D., a doctoral fellow from Stavanger University Hospital who conducted the research in the Buffalo Neuroimaging Analysis Centre (BNAC), is first author on both studies. The BNAC, housed in Kaleida Health's Buffalo General Hospital, is part of the Jacobs Neurological Institute, the Department of Neurology in the UB School of Medicine and Biomedical Sciences.

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 grey matter, the brain regions where those messages are received, interpreted and acted upon.

Using advanced magnetic resonance imaging (MRI) technologies available at the Buffalo Neuroimaging Analysis Centre (BNAC), the researchers can identify brain regions linked to Parkinson's disease based on images showing the status of both white and grey 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.

This study describes one of the first large-scale analyses of the extent of global (overall), tissue-specific and regional brain atrophy, and white matter hyperintensities (WMH). WMH are diseased areas of the white matter seen commonly in brain MRI scans in the elderly.

Results showed that in Parkinson's patients, white matter hyperintensities were associated significantly 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 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. Results were presented April 16.

Applying an MRI analytical process called voxel-based morphology, Dalaker and colleagues analysed high-resolution MRI scans of 43 newly diagnosed PD patients and those of 31 sex-matched normal controls.

They found that the PD patients with mild cognitive impairment showed a trend toward reduced grey 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 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-centre 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 subjects with similar age- and sex- distribution. The researchers plan to follow this sample for 10 years.