Planimetric Magnetic Resonance Parkinsonism Index (MRPI) can identify midbrain atrophy and differentiate PSP subjects. This figure shows the planes assessed, where the area of pons in midsagittal plane is shown in red, the area of midbrain in midsagittal plane is shown in brown, and the width of middle cerebellar and superior cerebellar peduncles are indicated as red lines.
MRPI = [(Pons/Midbrain x (Middle Cerebellar Peduncles/Superior Cerebellar Peduncles)]
The updated MRPI 2.0 extends the MRPI metric to include more ventricle variables, including the average width of the third ventricle and the distance between the frontal horns of the lateral ventricles.
MRPI 2.0 = MRPI x (Third Ventricle / Frontal Horns)
The planimetric biomarkers MRPI and MRPI 2.0, are effective at differentiating PSP subjects from other tauopathies, such as CBD and FTD. Mean +/- SD. * p<0.05; ** p<0.01; *** p<0.001; **** p<0.0001
Change over time of the planimetric biomarker in the PSP population also clearly illustrates the significant atrophy that occurs in the brainstem regions.
References
Quattrone, A., Morelli, M., Nigro, S., Quattrone, A., Vescio, B., Arabia, G., Nicoletti, G., Nisticò, R., Salsone, M., Novellino, F., Barbagallo, G., Le Piane, E., Pugliese, P., Bosco, D., Vaccaro, M.G., Chiriaco, C., Sabatini, U., Vescio, V., Stanà, C., Rocca, F., Gullà, D., Caracciolo, M. A new MR imaging index for differentiation of progressive supranuclear palsy-parkinsonism from Parkinson's disease. Parkinsonism Relat. Disord., 54: 3-8, 2018; doi: 10.1016/j.parkreldis.2018.07.016
Structural brain changes can be quantified using planimetric measurements, such as the Magnetic Resonance Parkinsonism Index (MRPI) and the improved MRPI 2.0, which are both ratios derived from multiple areas and distances within the midbrain, pons, cerebellar peduncles, and ventricles. We have implemented both MRPI and MRPI 2.0 measurements within our PIANO™ framework.
As illustrated in the bar graph, when MRPI and MRPI 2.0 are applied to a PSP population, the MRPI ratios are significantly larger compared to other tauopathies, such as Corticobasal Degeneration (CBD) and Frontotemporal Dementia (FTD).
The change over time of the planimetric biomarker in the PSP population also clearly illustrates the significant atrophy that occurs within the brainstem regions.