No effect of age, gender and total intracranial volume on brainstem MR planimetric measurements.

OBJECTIVES: MR planimetry of brainstem structures can be helpful for the discrimination of Parkinsonian syndromes. It has been suggested that ageing might influence brainstem MR measurements assessed by MR planimetry, while effects of gender and total intracranial volume (TIV) have not been assessed so far. The aim of this study was to evaluate age, gender and TIV effects on brainstem MR planimetric measures. METHODS: Brainstem MR planimetric measures of diameters (midbrain, pons, middle and superior cerebellar peduncle) and areas (pons and midbrain), the derived ratios, and the magnetic resonance Parkinsonism index (MRPI) were assessed on 1.5-T MR images in a large cohort of 97 healthy controls and analysed for the influence of age, gender and TIV with univariate and multivariate linear models. RESULTS: Neither gender nor age effects on planimetric measurements were observed in the population relevant for the differential diagnosis of neurodegenerative Parkinsonism, aged 50 to 80 years, except for single area-derived measurements, with gender effects on pontine area (p = 0.013) and age effects on midbrain area (p = 0.037). Results were similar upon inclusion of the TIV in the analyses. CONCLUSIONS: There is no need to correct for age, gender or TIV when using brainstem-derived MR planimetric measurements in the differential diagnosis of neurodegenerative Parkinsonism. KEY POINTS: • There were no gender effects on single or combined imaging measurements of the brainstem in the population aged 50 to 80 years, the age range relevant for the differential diagnosis of neurodegenerative Parkinsonism (except for pontine area). • There were no age effects on single or combined imaging measurements of the brainstem in the population aged 50 to 80 years, the age range relevant for the differential diagnosis of neurodegenerative Parkinsonism (except for midbrain area). • There is no need for age- or gender-specific cut-offs for the relevant age group.

MR planimetry in neurodegenerative parkinsonism yields high diagnostic accuracy for PSP.

INTRODUCTION: Several previous studies examined different brainstem-derived MR planimetric measures with regards to their diagnostic accuracy in separating patients with neurodegenerative parkinsonian disorders and reported conflicting results. The current study aimed to compare their performance in a well-characterized sample of patients with neurodegenerative parkinsonian disorders. METHODS: MR planimetric measurements were assessed in a large retrospective cohort of 55 progressive supranuclear palsy (PSP), 194 Parkinson's disease (PD) and 63 multiple system atrophy (MSA) patients. This cohort served as a training set used to build C4.5 decision tree models to discriminate PSP, PD and MSA. The models were validated in two independent test sets. The first test set comprised 84 patients with early, clinically unclassifiable parkinsonism (CUP). A prospective cohort of patients with PSP (n = 23), PD (n = 40) and MSA (n = 22) was exploited as a second test-set. RESULTS: The pons-to-midbrain diameter ratio, the midbrain diameter, the middle cerebellar peduncle width and the pons area were identified as the most predictive parameters to separate PSP, MSA and PD in C4.5 decision tree models derived from the training set. Using these decision models, AUCs in discriminating PSP, MSA and PD were 0.90, 0.57 and 0.73 in the CUP-cohort and 0.95, 0.61 and 0.87 in the prospective cohort, respectively. CONCLUSION: We were able to demonstrate that brainstem-derived MR planimetric measures yield high diagnostic accuracy for the discrimination of PSP from related disorders when decision tree algorithms are applied, even at early, clinically uncertain stages. However, their diagnostic accuracy in discriminating PD and MSA was suboptimal.