Magnetic Resonance Planimetry in the Differential Diagnosis between Parkinson’s Disease and Progressive Supranuclear Palsy

Abstract

The clinical differential diagnosis between Parkinson’s disease (PD) and progressive supranuclear palsy (PSP) is often challenging. The description of milder PSP phenotypes strongly resembling PD, such as PSP-Parkinsonism, further increased the diagnostic challenge and the need for reliable neuroimaging biomarkers to enhance the diagnostic certainty. This review aims to summarize the contribution of a relatively simple and widely available imaging technique such as MR planimetry in the differential diagnosis between PD and PSP, focusing on the recent advancements in this field. The development of accurate MR planimetric biomarkers, together with the implementation of automated algorithms, led to robust and objective measures for the differential diagnosis of PSP and PD at the individual level. Evidence from longitudinal studies also suggests a role of MR planimetry in predicting the development of the PSP clinical signs, allowing to identify PSP patients before they meet diagnostic criteria when their clinical phenotype can be indistinguishable from PD. Finally, promising evidence exists on the possible association between MR planimetric measures and the underlying pathology, with important implications for trials with new disease-modifying target therapies.

Brain MRI in Progressive Supranuclear Palsy with Richardson's Syndrome and Variant Phenotypes

“…Descriptive and manual planimetric MRI features are useful to support the diagnosis of PSP-RS. 13 This study FIG. 3.…”

“…Descriptive and manual planimetric MRI features are useful to support the diagnosis of PSP‐RS 13 . This study examined descriptive features and planimetric measures in a cohort representing the broad phenotypic PSP spectrum in clinical practice.…”

“…Several descriptive MRI features indicating midbrain atrophy have been proposed and are frequently reported in clinical routine including the hummingbird sign, the Mickey‐Mouse sign, and the morning‐glory sign 6‐8 . Various planimetric measures and combinations of planimetric measures have been validated in PSP, not exclusively focusing on the brain stem, but including adjacent structures such as the cerebellar peduncles 9‐14 . More recently, fully automated MRI analysis combining atlas‐based volumetry with support vector machine (SVM) classification has been proposed for the (differential) diagnosis of neurodegenerative parkinsonian syndromes including PSP 15 .…”

“…[6][7][8] Various planimetric measures and combinations of planimetric measures have been validated in PSP, not exclusively focusing on the brain stem, but including adjacent structures such as the cerebellar peduncles. [9][10][11][12][13][14] More recently, fully automated MRI analysis combining atlas-based volumetry with support vector machine (SVM) classification has been proposed for the (differential) diagnosis of neurodegenerative parkinsonian syndromes including PSP. 15 The added value of this investigator-independent approach beyond descriptive and planimetric measures has not been tested so far.…”

Differentiating between common PSP phenotypes using structural MRI: a machine learning study

“…Among the MR planimetric measures, most studies evaluated the midbrain/pons area ratio and the Magnetic Resonance Parkinsonism Index (MRPI). This latter index is a MR planimetric biomarker combining the midbrain area and the superior cerebellar peduncle width (normalized by pons area and middle cerebellar peduncle width respectively, as reference structures), which can be calculated by multiplying the pons/midbrain area ratio by the ratio between middle cerebellar peduncle width and superior cerebellar peduncle width [ 19 ]. A few imaging biomarkers, such as the MRPI 2.0 (a second version of MRPI, obtained by multiplying the MRPI value by the third ventricle width normalized by the frontal horns width) [ 28 , 29 ] and FDG-PET [ 26 ], showed good performances also in distinguishing PSP-P from PD patients.…”