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Lower body parkinsonism: rethinking MRI planimetry
Constança Jalles1, Rita M Simões2, Berfin Sakallioglu3
1Laboratory of Clinical Pharmacology and Therapeutics, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal; Clinical Pharmacology Unit, Unidade Local de Saúde de Santa Maria, Portugal.
Magnetic resonance imaging (MRI) biomarkers like MRPI 2.0 can differentiate Progressive Supranuclear Palsy (PSP) and normal pressure hydrocephalus (NPH) from vascular parkinsonism (VP) in lower body parkinsonism (LBP). Midbrain size reduction and ventricle enlargement are key LBP imaging features.
Area of Science:
- Neuroimaging
- Neurology
- Radiology
Background:
- Magnetic resonance imaging (MRI) planimetric biomarkers, including midbrain to pons (M/P) ratio, magnetic resonance parkinsonism index (MRPI), and MRPI 2.0, accurately diagnose Progressive Supranuclear Palsy (PSP) from Parkinson's Disease (PD) and other parkinsonisms.
- These biomarkers have not been evaluated in lower body parkinsonism (LBP), where distinguishing PSP from vascular parkinsonism (VP) and normal pressure hydrocephalus (NPH) is clinically crucial.
Purpose of the Study:
- To investigate the utility of MRI planimetric measures in LBP patients.
- To assess the role of these biomarkers in the differential diagnosis of LBP.
Main Methods:
- Retrospective analysis of MRI scans from 71 subjects.
- Included patients with diagnosed VP (n=23), NPH (n=12), PSP (n=23), and a control group with PD (n=13) without gait or postural issues.
- Evaluated MRI planimetric measures, ratios, and parkinsonism indexes.
Main Results:
- LBP groups (VP, NPH, PSP) exhibited smaller midbrain areas and wider third ventricles and frontal horns compared to the PD group.
- The PSP group showed the highest medians for P/M ratio, MRPI, and MRPI 2.0, significantly differing from other groups (except NPH).
- MRPI 2.0 effectively discriminated between PSP and NPH versus VP at a group level.
Conclusions:
- MRPI 2.0 aids in differentiating PSP and NPH from VP in LBP patients at a group level.
- Reduced midbrain size and enlarged ventricles (third and frontal horns) are potential key imaging indicators for the LBP phenotype, encompassing VP, NPH, and PSP, distinguishing them from PD.
