Objective: To evaluate age- and gender effects on brainstem MR-planimetric measures. (1,2).

Background: Brainstem planimetry has been successfully applied to differentiate Progressive Supranuclear Palsy (PSP) from Parkinson’s disease (PD), Multiple- System-Atrophy (MSA) and healthy controls (HC). It has been suggested that ageing might influence the brainstem midbrain-to-pontine-area-ratio (M/PA).

Methods: MR planimetry was performed in 97 HC (mean age 62.8 years; SD 10.9 years; female-to-male-ratio = 49:48) on a 1.5T scanner to assess midsagittal midbrain area, midsagittal pontine area, mean middle cerebellar peduncles (MCP) diameter, mean superior cerebellar peduncle (SCP) diameter, as well as midsagittal midbrain diameter (acc. QS) (2) and pontine diameter (acc. QS) (2). From these parameters, the MR-Parkinson- Index (MRPI) (1), midbrain-to-pons area ratio (M/PA) (1) as well as the midbrain-to-pontine-diameter-ratio (M/Pd) (2) were calculated. Planimetric measures were performed on an imaging database program (IMPAX EE). Gender-related differences of all MR-planimetric measurements as well as of the MRPI, M/PA and M/Pd were calculated using ANCOVAs entering gender as factor and age as covariate. Due to the multiple comparisons, p-values of < 0.01 were considered statistically significant.

Results: ANCOVA models revealed no significant gender-effects on any variable. However, ANCOVA models revealed significant age-effects on midbrain diameter (p < 0.0001; F 18.708), on the MRPI (p=0.513; F 0.431), the M/Pd (p < 0.0001; F 12.385) and the M/PA (p < 0.0001; F 24.764) when including all study participants. However, when including only the population aged 50 to 80, there was no significant age-effect on neither variable.

Conclusions: While there are no significant gender-effects on any brainstem MR planimetric measures, our data suggest significant age-effects on the midbrain diameter, midbrain-to-pontine-diameter-ratio (M/Pd), and midbrain-to-pons area ratio (M/PA). However, when applying MR-planimetric measures to controls aged 50 to 80, no age-effects on these brainstem MR planimetric measures were observed. This age-group is relevant for the differential diagnosis of neurodegenerative parkinsonism, thus suggesting that there is no need for age specific-cut offs for these brainstem MR planimetric measures. (1) Hussl A et al. Mov Disord. 2010;25(14):2444-9. (2) Massey LA et al. Neurology. 2013;80(20):1856-61.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effects-of-age-and-gender-on-brainstem-mr-planimetry/