Objective: To evaluate structural brain stem measurements to differentiate multiple system atrophy (MSA) from idiopathic Parkinson‘s disease (IPD).

Background: MSA is a sporadic, progressive, neurodegenerative disease of unknown aetiology. Depending on underlying subtype, clinical characteristics comprise predominantly parkinsonism or cerebellar ataxia with autonomic failure [1, 2]. Due to the symptom overlap with IPD and the fact that MSA can only be reliably diagnosed post-mortem, there is an urgent need for non-invasive methods, such as imaging biomarkers, to differentiate between the two diseases [3].

Method: 20 patients, diagnosed with MSA (no further classification) and 20 IPD patients matched for age and disease duration, were retrospectively enrolled. 40 individual midsagittal T1-weighted MRI scans were analysed using 3D Slicer v 4.11. (slicer.org). After the assessment of the major optical axis through the brain stem, midbrain and pons diameters (MBW;PW), as well as midbrain area and pons area (MBA;PA) were manually determined by two independent raters in all MRI scans, according to previously described methods[4]. Additionally, we calculated the midbrain-to-pons-ratio (MTPR) as well as the midbrain-to-pons-area-ratio (MTPAR) which were introduced as markers for differentiation of MSA and progressive supranuclear palsy(PSP)[4-6].

Results: Mann-Whitey-U test revealed significantly smaller PW in MSA (M=16.72±2.58 mm) when compared to IPD (M=18.43±1.55 mm): U=121.00, p=.016. Additionally, the PA was significantly smaller in MSA (M=525.16±104.98 mm²) when compared to IPD (M=600.02±67.33 mm²): U=117.00, p=.012. Midbrain measures were not significantly different between the groups (p=.070). MTPAR and MTPR also did not show significant differences between the groups (p=.301).

Conclusion: In accordance with previously results, we found significant atrophy of the pons in MSA when compared to IPD [7]. However, we found no significant difference in MTPR and MTPAR between the groups, which suggests that these two ratios are not suitable for distinguishing MSA and IPD.

References: 1. Carré, G., et al., Brain MRI of multiple system atrophy of cerebellar type: a prospective study with implications for diagnosis criteria. J Neurol, 2020. 267(5): p. 1269-1277.
2. Chelban, V., et al., An update on MSA: premotor and non-motor features open a window of opportunities for early diagnosis and intervention. J Neurol, 2020. 267(9): p. 2754-2770.
3. Gilman, S., et al., Consensus statement on the diagnosis of multiple system atrophy. J Neurol Sci, 1999. 163(1): p. 94-8.
4. Cui, S.S., et al., Midbrain/pons area ratio and clinical features predict the prognosis of progressive Supranuclear palsy. BMC Neurol, 2020. 20(1): p. 114.
5. Chelban, V., et al., An update on advances in magnetic resonance imaging of multiple system atrophy. J Neurol, 2019. 266(4): p. 1036-1045.
6. Massey, L.A., et al., The midbrain to pons ratio: a simple and specific MRI sign of progressive supranuclear palsy. Neurology, 2013. 80(20): p. 1856-61.
7. Paviour, D.C., et al., Longitudinal MRI in progressive supranuclear palsy and multiple system atrophy: rates and regions of atrophy. Brain, 2006. 129(Pt 4): p. 1040-9.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/evaluation-of-structural-brain-stem-measurements-for-the-differential-diagnosis-of-msa-and-ipd/