Introduction

Approximately 80% of facial nerve paralysis is idiopathic and unilateral, known as Bell’s palsy^[1,2]. The facial nerve is the main motor pathway to the facial muscles and is involved in regulaling facial expressions and facial movements^[3]. Bell’s palsy can have enormous psychological impact on patients, prompting extensive research on brain function reorganization related to this condition to understand the mechanism of functional integration within the cerebral cortex and to identify effective treatments.

Purpose

To investigate the difference of brain fALFF and FC in patients with left and right early Bell’s palsy using resting-state functional magnetic resonance imaging (R-fMRI). In addition, correlations between altered FC and clinical presentation scores were analyzed in the left and right facial palsy groups

Materials and methods

Sixty-seven patients and 37 age- and sex-matched healthy controls were scanned at 3.0 T with a axial resting state blood oxygen-level dependent MRI and a sagittal 3D fast spoiled gradient-echo sequences. Regional brain activity was analyzed by comparing the fALFF between left and right palsy groups. The altered brain regions were further selected as seeds in the subsequent inter-group and inter-regional FC analyses after data preprocess with statistical parametric mapping (SPM) soft, and the analysis of the correlations between Toronto Facial Grading System (TFGS) scores and the altered connectivities was also implemented.

Results

Compared with the left Bell’s palsy group, the right Bell’s palsy group showed several brain regions with different fALFF values (Fig.1). The mean of the overall FC of every region showed significant group differences (Fig.2) and decreased connectivities were observed in the right supramarginal gyrus (SMG), bilateral superior frontal gyrus (SFG), and left precentral gyrus (PreCG) in the left palsy group. Compared with those of the right palsy group, the paired brain regions with lower FC in the left palsy group were left temporal pole of the superior temporal gyrus (TPOsup) and right SMG, left TPOsup and middle cingulate cortex (MCC), left TPOsup and left PreCG, right SMG and SFG, MCC and left PreCG, left and right SFG, and right SFG and left PreCG (Fig.3). In the left Bell’s palsy group, the TPOsup and right SMG, and right SMG and right SFG paired regions demonstrated a negative correlation with the TFGS scores. In the right Bell’s palsy group, the left TPOsup and PreCG indicated a negative correlation with the TFGS scores, and the right SFG and left PreCG illustrated a postive correlation with the TFGS scores (Fig.4).

Conclusion

The fALFF and FC analyses revealed remodeling of different brain functional networks in patients with early Bell’s palsy. The reintegrating mechanisms differed between patients with left and right Bell’s palsy. And the severity of the disease showed different association with altered FC related to sensory transmission and motor regulation between bilateral patients. Exercise rehabilitation therapy which could increase facial muscles stimulation and nerve transmission actions should be given more attention in the early treatment.

Acknowledgements

No acknowledgement found.

References

1. Song W, Cao Z, Lang C, Dai M, Xuan L, Lv K, Cui F, Jorgenson K, Xu M, Kong J. Disrupted functional connectivity of striatal sub-regions in Bell’s palsy patients. Neuroimage Clin 2017;14: 122-9.
2. Han X, Li H, Wang X, Zhu Y, Song T, Du L, Sun S, Guo R, Liu J, Shi S, Fu C, Gao W, Zhang L and Ma G. Altered brain fraction amplitude of low frequency fluctuation at resting state in patients with early left and right bell’s palsy: do they have differences? Front. Neurosci 2018;12:797. doi: 10.3389/fnins.2018.00797.
3. Tianbin Song, Xiaowei Han, Lei Du, Jing Che, Jing Liu, Sumin Shi, Chao Fu, Wenwen Gao, Jie Lu, Guolin Ma. The role of neuroimaging in the diagnosis and treatment of depressive disorder: a recent review. current pharmaceutical design. 2018; 24:1-9.