Conventional 3T brain MRI and diffusion tensor imaging in the diagnostic workup of early stage parkinsonism

Abstract

Introduction: The aim of this study is to evaluate whether the diagnostic accuracy of 3 T brain MRI is improved by region of interest (ROI) measures of diffusion tensor imaging (DTI), to differentiate between neurodegenerative atypical parkinsonism (AP) and Parkinson's disease (PD) in early stage parkinsonism.

Methods: We performed a prospective observational cohort study of 60 patients presenting with early stage parkinsonism and initial uncertain diagnosis. At baseline, patients underwent a 3 T brain MRI including DTI. After clinical follow-up (mean 28.3 months), diagnoses could be made in 49 patients (30 PD and 19 AP). Conventional brain MRI was evaluated for regions of atrophy and signal intensity changes. Tract-based spatial statistics and ROI analyses of DTI were performed to analyze group differences in mean diffusivity (MD) and fractional anisotropy (FA), and diagnostic thresholds were determined. Diagnostic accuracy of conventional brain MRI and DTI was assessed with the receiver operating characteristic (ROC).

Results: Significantly higher MD of the centrum semiovale, body corpus callosum, putamen, external capsule, midbrain, superior cerebellum, and superior cerebellar peduncles was found in AP. Significantly increased MD of the putamen was found in multiple system atrophy-parkinsonian form (MSA-P) and increased MD in the midbrain and superior cerebellar peduncles in progressive supranuclear palsy (PSP). The diagnostic accuracy of brain MRI to identify AP as a group was not improved by ROI measures of MD, though the diagnostic accuracy to identify MSA-P was slightly increased (AUC 0.82 to 0.85).

Conclusion: The diagnostic accuracy of brain MRI to identify AP as a group was not improved by the current analysis approach to DTI, though DTI measures could be of added value to identify AP subgroups.

Fig. 1

Regions of interest in the bilateral putamen (a), midbrain (b), and superior cerebellar peduncles (c). Mean MD and FA of these ROIs were calculated

Fig. 2

TBSS analyses of atypical parkinsonism with Parkinson’s disease and atypical parkinsonism subgroups with Parkinson’s disease. Upper row: TBSS comparison of AP (n = 19) with PD (n = 29). Brain regions with statistically significant lower FA and higher MD in AP in comparison to PD (p < 0.05). Middle row: TBSS comparison of MSA-P (n = 12) with PD (n = 29). MD of the left putamen and external capsule, and superior part of the cerebellar vermis proved to be statistically significant higher for MSA-P in comparison to PD (p < 0.05). A part of the left external capsule demonstrated significantly lower FA in MSA-P. Lower row: TBSS comparison of DLB (n = 3) with PD (n = 29). No statistically significant differences were demonstrated, while at a p value of <0.1 lower FA and higher MD in the left frontal lobe is seen for DLB in comparison PD. No differences were demonstrated in a TBSS comparison between PSP and PD. Red, lower values; blue, higher values

Fig. 3

Boxplots of MD values (mm²/s) of the putamen, midbrain, and SCP. Horizontal lines indicate the defined threshold MD values to discriminate AP from PD (putamen and midbrain MD values of 0.9 × 10 and 1.1 × 10⁻³ mm²/s for the SCP). PD Parkinson’s disease, AP neurodegenerative atypical parkinsonism, MSA-P multiple system atrophy–parkinsonian form, PSP progressive supranuclear palsy, DLB dementia with Lewy bodies, SCP superior cerebellar peduncle

Fig. 4

ROC curves of brain MRI and DTI to identify neurodegenerative atypical parkinsonism as a group (left) and MSA-P (right). Conventional brain MRI (1), DTI (2), and MRI with DTI combined (3). Quantitative DTI measures of DTI did not increase the diagnostic accuracy of brain MRI for the diagnosis of AP as a group: AUC 0.83 (95 % CI 0.70–0.95). The AUC for the MRI diagnosis of MSA-P was slightly increased by MD of the putamen: AUC 0.82 (95 % CI 0.69–0.96) was increased to 0.85 (95 % CI 0.71–0.98). AUC area under the curve, CI confidence interval, MSA-P multiple system atrophy–parkinsonian form