Elsevier

Clinical Neurophysiology

Volume 122, Issue 1, January 2011, Pages 121-127
Clinical Neurophysiology

Regional homogeneity changes in patients with neuromyelitis optica revealed by resting-state functional MRI

https://doi.org/10.1016/j.clinph.2010.05.026Get rights and content

Abstract

Objective

Resting-state brain activity in neuromyelitis optica (NMO) patients can give clues to the pathophysiology of the disorder, and may be helpful in diagnosis; however, it has been less explored using functional MRI (fMRI). In the current study, we used a regional homogeneity (ReHo) method to investigate NMO-related modulations of neural activity in the resting state.

Methods

Resting-state fMRIs acquired in 17 NMO patients as well as in 17 age- and sex-matched normal controls were compared. Kendall’s coefficient of concordance was used to measure the regional homogeneity. Correlative analyses were performed to explore the relationship between the expanded disability status scale (EDSS), disease duration and ReHo in regions with significant group differences.

Results

Comparing the NMO group with the healthy controls, we found ReHo decreased in extensive brain regions, including the left anterior cingulate, left medial frontal gyrus, left posterior cingulate, right precuneus and right middle temporal gyrus; and increased in the right inferior frontal gyrus.

Conclusions

These results demonstrate that neural activity in the resting state is changed in patients with NMO.

Significance

The present study reveals clear abnormalities of NMO patients in the baseline activities that have not been well detected, and further improves our understanding of the neural substrates of cognitive impairment in NMO patients.

Introduction

Neuromyelitis optica (NMO) is an inflammatory, demyelinating syndrome of the central nervous system that is characterised by severe attacks of optic neuritis and myelitis (Wingerchuk et al., 2006, Wingerchuk et al., 2007). Although the brain was traditionally regarded as healthy (Lennon et al., 2004, Pittock et al., 2006), cognitive impairment in NMO patients was reported only recently (Blanc et al., 2008). Some functional magnetic resonance imaging (fMRI) studies have been performed to examine the differences between NMO patients and normal controls (Rocca et al., 2004). Resting-state fMRI, as a new branch of functional imaging, can reflect the baseline brain activity. The low-frequency fluctuations of the resting-state fMRI signal were suggested to be of physiological importance and reflect spontaneous neuronal activity (Biswal et al., 1995, Zang et al., 2007). However, baseline brain activity of NMO patients is still less explored using resting-state fMRI.

Recently, a new method, regional homogeneity (ReHo), has been developed to analyse the blood-oxygen-level dependent (BOLD) signal of the brain (Zang et al., 2004). ReHo assumes that within a functional cluster, the haemodynamic characteristics of every voxel would be similar or synchronous with that of each other; and such similarity could be changed or modulated by different conditions (Zang et al., 2004). ReHo has been successfully used to investigate the functional modulations in the resting state in patients with Alzheimer’s disease (AD) (He et al., 2007), schizophrenia (Liu et al., 2006) and Parkinson’s disease (Wu et al., 2009). In the current study, we used this method to investigate NMO-related brain neural activity in the resting state.

Section snippets

Subjects

We studied 17 patients with NMO (two males, 15 females; mean age 37.2 years, SD 12.1, age range 19–59 years), and 17 age- and sex-balanced healthy subjects (mean age 36.9 years, SD 11.2, age range 19–59 years). The subjects were all right-handed as measured by the Edinburgh Inventory (Oldfield, 1971). The diagnosis of NMO was according to the recently revised diagnostic criteria (optic neuritis, acute myelitis, contiguous spinal cord MRI lesion extending over ⩾3 vertebral segments, brain MRI not

Results

T1WI, T2WI and FLAIR images of each subject were evaluated by two experienced neuroradiologists, Yunyun Duan and Yaou Liu, and no brain lesions were detected for all subjects (including NMO patients and healthy controls). To evaluate grey matter atrophy in NMO patients, T1-weighted three-dimensional (3D) MRI data of NMO patients and healthy controls were analysed using a voxel-based morphometry (VBM) method (as shown in Appendix A).

Discussion

The physiological background of the ReHo measures (using KCC) is that a given voxel is temporally similar to that of its neighbours in rest/task conditions (Lu et al., 2003, Zang et al., 2004). ReHo has been used in the purification of the activated clusters (Baumgartner et al., 1999), which is not well dealt with in both data-driven and model-driven methods (Baumgartner et al., 1999, Goutte et al., 1999). In the current study, ReHo was used as an independent method in the analysis of

Acknowledgements

This work was supported by the State Key Program of National Natural Science of China (NO. 30930029) and the National Natural Science Foundation of China (NO. 30770620, NO. 60775039). Dr. Yaou Liu was supported by the McDonald Fellowship from the Multiple Sclerosis International Federation (MSIF).

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