Considering total intracranial volume and other nuisance variables in brain voxel based morphometry in idiopathic PD

Abstract

Voxel-based morphometry (VBM) studies of Parkinson's disease (PD), have yielded mixed results, possibly due to several studies not accounting for common nuisance variables (age, sex, and total intracranial volume [TICV]). TICV is particularly important because there is evidence for larger TICV in PD. We explored the influence of these covariates on VBM by 1) comparing PD patients and controls before adding covariates, after adding age and sex, and after adding age, sex and TICV, and 2) by comparing controls split into large and small TICV before and after controlling for TICV, with age and sex accounted for in both analyses. Experiment 1 consisted of 40 PD participants and 40 controls. Experiment 2 consisted of 88 controls median split by TICV. All participants completed an MRI on a 3 T scanner. TICV was calculated as gray + white + CSF from Freesurfer. VBM was performed on T1 images using an optimized VBM protocol. Volume differences were assessed using a voxel-wise GLM analysis. Clusters were considered significant at >10 voxels and p < .05 corrected for familywise error. Before controlling for covariates, PD showed reduced GM in temporal, occipital, and cerebellar regions. Controlling for age and sex did not affect the pattern of significance. Controlling for TICV reduced the size of the significant region although it still contained portions of bilateral temporal lobes, occipital lobes and cerebellum. The large TICV group showed reduced volume in temporal, parietal, and cerebellar areas. None of these differences survived controlling for TICV. This demonstrates that TICV influences VBM results independently from other factors. Controlling for TICV in VBM studies is recommended.

White matter hyperintensities are linked to future cognitive decline in de novo Parkinson's disease patients

“…The ranges of the WMH loads found in this study for both control and de novo PD populations (mean value of 7 CCs = 0.37% of the total intracranial volume) were similar to values reported in other normal aging studies, suggesting that similar trends of decline can be expected in such populations as well ( De Marco et al, 2017 ; Huang et al, 2018 ; Wiseman et al, n.d. ; Zhang et al, 2018 ).…”

Serum Insulin-Like Growth Factor-1 in Parkinson's Disease; Study of Cerebrospinal Fluid Biomarkers and White Matter Microstructure

“…On the other hand, normal aging is shown to be more confined to the frontal circuit with the coexistence of disruptions in the genu and anterior cingulum ( 53 ). There are also several reports of the centrality of lower integrity of CC and cingulum in relation with poorer cognition and transition to demented state in patients with PD ( 54 – 58 ). Of note, the prefrontal white matter is the most consistently described region in PD ( 33 ), considering the executive dysfunction as the main cognitive disturbance in this neurodegenerative disorder ( 59 ).…”

Psychological Factors Associated with Phantom Limb Pain: A Review of Recent Findings

“…This suggests that phantom sensations in general [ 119 ] and PLP in particular are associated with impairments in the body schema, describing a flexible central representation of body posture that is needed for action. Since mental rotation of body parts involves motor imagery processes [ 120 ], and since the associated neural mechanisms are different in amputees with PLP compared to amputees without PLP [ 121 ], these results highlight the impaired mentalization of motor execution specifically for painful phantom limbs. Consequently, it has been suggested that the central body representation itself should be a target of therapeutic approaches [ 122 ], and thus, novel treatments aim at normalizing the underlying processes [ 123 – 130 ].…”