Koji Kamagata
Parkinson disease (PD) is the second most frequent neurodegenerative disorder after Alzheimer disease.1 In PD, the primary pathologic changes involve loss of nigrostriatal dopaminergic neurons and the presence of Lewy bodies (α-synuclein–immunoreactive inclusions), with neuronal loss in numerous brain regions.2 To distinguish these pathophysiologic changes in PD, conventional MR imaging has so far been unsuccessful. A noninvasive technology such as diffusion tensor imaging would be helpful for understanding changes at the microstructural level, as well as for monitoring disease progression and improving prognosis in terms of these aspects of PD.
Dementia is one of the most common and important nonmotor symptoms of PD, and greatly affects functioning and quality of life.3 It increases caregiver burden, health-related costs,4 and duration of hospital stays.5 Therefore, early diagnosis and intervention in cognitive impairment of PD is very important. Although demographic and clinical characteristics can be used to help estimate variations in the rate of cognitive decline and time to dementia in PD, objective biomarkers (such as MRI findings) are also needed.
Therefore, we compared diffusion abnormalities in the cingulate fibers in patients with PD with and without dementia, and healthy controls by using diffusion tensor tractography. As a result, there was a significant correlation between the Mini-Mental State Examination score and fractional anisotropy (FA) value in the anterior cingulate fiber tracts (r = 0.633, P <.05) in patients with PD with dementia. FA measured in the anterior cingulate fiber tracts was significantly lower in patients with PD and PD with dementia than in healthy controls (P =.003, P = .003). FA measured in the posterior cingulate fiber tracts was significantly lower in patients with PD with dementia than in healthy controls (P =.002).