Cerebral functional deficits in patients with ankylosing spondylitis- an fMRI study

Neurological impairment plays an important role in the development of Ankylosing spondylitis (AS). Early diagnosis and detection of it may stop the progress of neurological complications and improve the quality of patients' lives greatly. Somatosensory evoked potential (SSEP) and magnetic motor evoked potentials (MEP) have been proved useful to detect neurological impairments of AS. This study aimed to investigate the cerebral function deficits of AS using functional MRI technology. Twenty seven patients with AS and 28 control subjects were included in this study. All of them underwent structural MRI and resting state-functional MRI (rs-fMRI) scanning. Comparisons of amplitude of low frequency fluctuations (ALFF) of rs-fMRI signals between AS patients and normal controls were performed using two sample t-tests. To examine functional connectivity within the groups, one-sample t tests were performed on the individual z-value maps. The z values were compared between the two groups using two-sample t test. Partial correlations between rs-fMRI measures (ALFF and functional connectivity) of the brain regions which showed group difference and clinical results including the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score, the serum high-sensitivity C-reactive protein (hsCRP), and the erythrocyte sedimentation rate (ESR) were analyzed for AS patients. Compared with normal controls, the AS patients exhibited significant lower ALFF in the left medial frontal gyrus, the right precentral gyrus and the right posterior cingulate, while higher ALFF in the left cerebellum anterior lobe, the left middle temporal gyrus, the left superior occipital gyrus, the left postcentral gyrus and the right precuneus. AS patients showed widespread brain connectivity alterations. Functional connectivity strength of the left precuneus and the left middle temporal gyrus were closely correlated with the the BASDAI scores, ESR and hsCRP in AS patients. Our results enhance the understanding of the pathomechanism of AS and suggest that Rs-fMRI may be a helpful tool in the clinical detection and evaluation of neurological impairment in AS.