Applications of Functional Magnetic Resonance Imaging in Determining the Pathophysiological Mechanisms and Rehabilitation of Spatial Neglect

Recent advances in treatment of spatial neglect: networks and neuropsychology

INTRODUCTION

Spatial neglect remains an underdiagnosed and undertreated consequence of stroke that imposes significant disability. A growing appreciation of brain networks involved in spatial cognition is helping us to develop a mechanistic understanding of different therapies under development.

AREAS COVERED

This review focuses on neuromodulation of brain networks for the treatment of spatial neglect after stroke, using evidence-based approaches including 1) Cognitive strategies that are more likely to impact frontal lobe executive function networks; 2) Visuomotor adaptation, which may depend on the integrity of parietal and parieto- and subcortical-frontal connections and the presence of a particular subtype of neglect labeled Aiming neglect; 3) Non-invasive brain stimulation that may modulate relative levels of activity of the two hemispheres and depend on corpus callosum connectivity; and 4) Pharmacological modulation that may exert its effect primarily via right-lateralized networks more closely involved in arousal.

EXPERT OPINION

Despite promising results from individual studies, significant methodological heterogeneity between trials weakened conclusions drawn from meta-analyses. Improved classification of spatial neglect subtypes will benefit research and clinical care. Understanding the brain network mechanisms of different treatments and different types of spatial neglect will make possible a precision medicine treatment approach.

Resting motor threshold in the course of hand motor recovery after stroke: a systematic review

Background

Resting motor threshold is an objective measure of cortical excitability. Numerous studies indicate that the success of motor recovery after stroke is significantly determined by the direction and extent of cortical excitability changes. A better understanding of this topic (particularly with regard to the level of motor impairment and the contribution of either cortical hemisphere) may contribute to the development of effective therapeutical strategies in this cohort.

Objectives

This systematic review collects and analyses the available evidence on resting motor threshold and hand motor recovery in stroke patients.

Methods

PubMed was searched from its inception through to 31/10/2020 on studies investigating resting motor threshold of the affected and/or the non-affected hemisphere and motor function of the affected hand in stroke cohorts.

Results

Overall, 92 appropriate studies (including 1978 stroke patients and 377 healthy controls) were identified. The analysis of the data indicates that severe hand impairment is associated with suppressed cortical excitability within both hemispheres and with great between-hemispheric imbalance of cortical excitability. Favorable motor recovery is associated with an increase of ipsilesional motor cortex excitability and reduction of between-hemispheric imbalance. The direction of change of contralesional motor cortex excitability depends on the amount of hand motor impairment. Severely disabled patients show an increase of contralesional motor cortex excitability during motor recovery. In contrast, recovery of moderate to mild hand motor impairment is associated with a decrease of contralesional motor cortex excitability.

Conclusions

This data encourages a differential use of rehabilitation strategies to modulate cortical excitability. Facilitation of the ipsilesional hemisphere may support recovery in general, whereas facilitation and inhibition of the contralesional hemisphere may enhance recovery in severe and less severely impaired patients, respectively.

Aberrant brain voxel-wise resting state fMRI in patients with thyroid-associated ophthalmopathy

BACKGROUND AND PURPOSE

Although ophthalmic complaints were mostly mentioned in thyroid-associated ophthalmopathy (TAO), emotional and psychological disturbances are increasingly concerned. We aimed to investigate the brain functional alteration in TAO patients by using resting-state functional MRI (rs-fMRI) with the fractional amplitude of low-frequency fluctuation (fALFF), regional homogeneity (ReHo), and degree centrality (DC) methods.

METHODS

Twenty-one consecutive TAO patients and 21 healthy controls (HCs) underwent rs-fMRI scans. The fALFF, ReHo, and DC values were compared between groups.

RESULTS

Compared with HCs, TAO group showed decreased fALFF values in bilateral calcarine/left lingual gyrus and left middle occipital gyrus (MOG). Moreover, TAO group had decreased ReHo values in left MOG/inferior occipital gyrus/fusiform gyrus, while increased ReHo values in bilateral middle frontal gyrus (MFG)/superior frontal gyrus (SFG) than HCs. TAO group also showed decreased DC values in bilateral postcentral gyrus (PoCG)/precentral gyrus/superior parietal lobule and supplementary motor area, and increased DC values in left SFG/MFG and MFG. In TAO patients, ReHo value in left MOG was positively correlated with visual acuity (r = 0.524, p = 0.021), while ReHo values in bilateral MFGs were negatively correlated with cognitive scores (left/right: r = -0.476/-0.527, p = 0.039/0.020). DC value in left PoCG was negatively correlated with disease duration (r = -0.492, p = 0.033).

CONCLUSIONS

Our findings indicated that TAO patients had brain functional alterations in the visual network, executive control network, sensorimotor network, and attention network, which may reflect potential visual and cognitive dysfunctions.