Diffusion tensor imaging in parkinsonian syndromes: a systematic review and meta-analysis

Abstract

Objectives: We performed a systematic review to assess alterations in measures of diffusion tensor imaging (DTI) in parkinsonian syndromes, exploring the potential role of DTI in diagnosis and as a candidate biomarker.

Methods: We searched EMBASE and Medline databases for DTI studies comparing parkinsonian syndromes or related dementias with controls or another defined parkinsonian syndrome. Key details for each study regarding participants, imaging methods, and results were extracted. Estimates were pooled, where appropriate, by random-effects meta-analysis.

Results: Of 333 results, we identified 43 studies suitable for inclusion (958 patients, 764 controls). DTI measures detected alterations in all parkinsonian syndromes, with distribution varying differentially with disease type. Nine studies were included in a meta-analysis of the substantia nigra in Parkinson disease. A notable effect size was found for lowered fractional anisotropy in the substantia nigra for patients with Parkinson disease vs controls (-0.639, 95% confidence interval -0.860 to -0.417, p < 0.0001).

Conclusion: DTI may be a promising biomarker in parkinsonian syndromes and have a future role in differential diagnosis. Larger cohort studies are required to investigate some encouraging preliminary findings. Given the complexity of the parkinsonian syndromes, it is likely that any potential DTI biomarker would be used in combination with other relevant biomarkers.

Figure 1. Summary of study selection

DBS = deep brain stimulation; DTI = diffusion tensor imaging.

Figure 2. Overview of fractional anisotropy alterations in parkinsonian syndromes

Illustration showing regions where ≥3 studies individually detected a significant (p < 0.05) alteration in fractional anisotropy (FA) in comparison with healthy controls. (A) Parkinson disease (PD): substantia nigra (n = 7 studies) and frontal lobe (n = 4). (B) Progressive supranuclear palsy (PSP): corpus callosum (n = 5) and frontal lobe (n = 3). (C) Multiple system atrophy (MSA): cerebellum (n = 5), middle cerebellar peduncle (n = 6), pons (n = 4), and internal capsule (n = 3). All alterations were reductions in FA apart from 1 instance of increase in PSP in the corpus callosum.

Figure 3. Meta-analysis for substantia nigra fractional anisotropy in Parkinson disease vs controls

CI = confidence interval; PD = Parkinson disease.