Cortical Morphology in Patients with Orthostatic Intolerance

Subcortical brain segment volumes in Gulf War Illness and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

AIMS

There is controversy about brain volumes in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (CFS) and Gulf War Illness (GWI). Subcortical regions were assessed because of significant differences in blood oxygenation level dependent signals in the midbrain between these diseases.

MATERIALS AND METHOD

Magnetization-prepared rapid acquisition with gradient echo (MPRAGE) images from 3 Tesla structural magnetic resonance imaging scans from sedentary control (n = 34), CFS (n = 38) and GWI (n = 90) subjects were segmented in FreeSurfer. Segmented subcortical volumes were regressed against intracranial volume and age, then iteratively analyzed by multivariate general linear modeling with disease status, gender and demographics as independent co-variates.

KEY FINDINGS

The optimal model for all subjects used disease status and gender as fixed factors with independent variables eliminated after iteration. Volumes of anterior and midanterior corpus callosum were significantly larger in GWI than CFS. Gender was a significant variable for many segment volumes, and so female and male subjects were analyzed separately. CFS females had smaller left putamen, right caudate and left cerebellum white matter than control women. CFS males had larger left hippocampus than GWI males. Orthostatic status and posttraumatic distress syndrome were not significant covariates.

SIGNIFICANCE

CFS and GWI were appropriate "illness controls" for each other. The different patterns of adjusted segment volumes suggested that sexual dimorphisms contributed to pathological changes. Previous volumetric studies may need to be reevaluated to account for gender differences. The findings are framed by comparison to the spectrum of magnetic resonance imaging outcomes in the literature.

Delayed orthostatic hypotension in Parkinson's disease

Orthostatic hypotension (OH) is relatively common in the early stage of Parkinson's disease (PD). It is divided into delayed OH and classical OH. Classical OH in PD has been investigated widely, however, the clinical implications of delayed OH in PD have seldom been studied. The purpose of this study is to characterize delayed OH in PD. A total of 285 patients with early drug-naïve PD were enrolled and divided into three groups according to orthostatic change: no-OH, delayed OH, and classical OH. The disease severity in terms of motor, non-motor, and cognitive functions was assessed. The cortical thickness of 82 patients was analyzed with brain magnetic resonance imaging. The differences among groups and linear tendency in the order of no-OH, delayed OH, and classical OH were investigated. Seventy-seven patients were re-evaluated. Initial and follow-up evaluations were explored to discern any temporal effects of orthostasis on disease severity. Sixty-four (22.5%) patients were defined as having delayed OH and 117 (41.1%) had classical OH. Between-group comparisons revealed that classical OH had the worst outcomes in motor, non-motor, cognitive, and cortical thickness, compared to the other groups. No-OH and delayed OH did not differ significantly. Linear trends across the pre-ordered OH subtypes found that clinical parameters worsened along with the orthostatic challenge. Clinical scales deteriorated and the linear gradient was maintained during the follow-up period. This study suggests that delayed OH is a mild form of classical OH in PD. PD with delayed OH has milder disease severity and progression.

Is postural orthostatic tachycardia syndrome (POTS) a central nervous system disorder?

Postural orthostatic tachycardia syndrome (POTS), a disorder of the autonomic nervous system characterized by a rise in heart rate of at least 30 bpm from supine to standing position, has been traditionally viewed as a dysfunction of the peripheral nervous system. However, recent studies and evidence from overlapping conditions suggest that in addition to being considered a disorder of the peripheral nervous system, POTS should be viewed also as a central nervous system (CNS) disorder given (1) significant CNS symptom burden in patients with POTS; (2) structural and functional differences found on neuroimaging in patients with POTS and other forms of orthostatic intolerance; (3) evidence of cerebral hypoperfusion and possible alteration in cerebrospinal fluid volume, and (4) positive response to medications targeting the CNS and non-pharmacologic CNS therapies. This review outlines existing evidence of POTS as a CNS disorder and proposes a hypothetical model combining key mechanisms in the pathophysiology of POTS. Redefining POTS as a CNS disorder can lead to new possibilities in pharmacotherapy and non-pharmacologic therapeutic interventions in patents affected by this disabling syndrome.

Alterations of brain network hubs in reflex syncope: Evidence from a graph theoretical analysis based on DTI

OBJECTIVE

We evaluated global topology and organization of regional hubs in the brain networks and microstructural abnormalities in the white matter of patients with reflex syncope.

METHODS

Twenty patients with reflex syncope and thirty healthy subjects were recruited, and they underwent diffusion tensor imaging (DTI) scans. Graph theory was applied to obtain network measures based on extracted DTI data, using DSI Studio. We then investigated differences in the network measures between the patients with reflex syncope and the healthy subjects. We also analyzed microstructural abnormalities of white matter using tract-based spatial statistics analysis (TBSS).

RESULTS

Measures of global topology were not different between patients with reflex syncope and healthy subjects. However, in reflex syncope patients, the strength measures of the right angular, left inferior frontal, left middle orbitofrontal, left superior medial frontal, and left middle temporal gyrus were lower than in healthy subjects. The betweenness centrality measures of the left middle orbitofrontal, left fusiform, and left lingual gyrus in patients were lower than those in healthy subjects. The PageRank centrality measures of the right angular, left middle orbitofrontal, and left superior medial frontal gyrus in patients were lower than those in healthy subjects. Regarding the analysis of the white matter microstructure, there were no differences in the fractional anisotropy and mean diffusivity values between the two groups.

CONCLUSIONS

We have identified a reorganization of network hubs in the brain network of patients with reflex syncope. These alterations in brain network may play a role in the pathophysiologic mechanism underlying reflex syncope.