Subjects
the outpatients of the Department of Neurology at Shanghai Ninth People’s Hospital, China. These patients were diagnosed with SSD by a neurologist based on the Structured Clinical Interview from the DSM-5 [1]. Exclusion criteria for patients included: (1) those with other major psychiatric illness, including depression, anxiety, substance abuse, or dependence; (2) those with primary neurological illness, including dementia or stroke; and (3) those with any white matter changes, such as infarction or other vascular lesions detected by T2-weighted MRI. During the interview, the neurologist also obtained SSD demographic and clinical data, including age, sex, disease duration, Patient Health Questionnaire (PHQ-9), Generalized Anxiety Disorder (GAD-7), Hamilton Anxiety Scale (HAMA), Hamilton Depression Scale (HAMD) and Mini-mental State Examination (MMSE) scores. Of the SSD patients, 18 patients complained of headache (with and without dizziness), 8 patients complained of dizziness, 5 patients complained of peripheral pain, and 14 patients complained of other physical discomfort, such as local numbness. Half of the patients are drug-naive, and the rest were stopped on the day of the MRI scan. Forty-three age- and gender-matched healthy controls (19 males, 24 females) were recruited. All subjects were right-handed and had no substance abuse, and all neurological and psychiatric disorders were excluded based on clinical examination and structured interviews. The details are provided in Table 1.
Mri Acquisition
Functional and structural MRI data were acquired using a 3.0 T Siemens Prisma system that utilized a 64-channel head coil at the Shanghai Key Laboratory of Magnetic Resonance (East China Normal University, Shanghai, China). During scanning, custom-fit foam pads were used to minimize each subject’s head movements. We obtained the whole-brain anatomical volume using a high-resolution T1-weighted 3-dimensional magnetization-prepared rapid-acquisition gradient-echo (MPRAGE) pulse sequence with the parameters as follows: repetition time = 2530 ms, echo time = 2.34 ms, inversion time = 1100 ms, flip angle = 7°, number of slices = 192, sagittal orientation, field of view = 256 × 256 mm2, matrix size = 256 × 256, and slice thickness = 1 mm with a 50% gap. The resting-state fMRI images were acquired using a T2*-weighted gradient-echo echo-planar imaging (EPI) pulse sequence with the following parameters: repetition time = 2000 ms, echo time = 30 ms, flip angle = 90°, field of view = 220 × 220 mm2, matrix size = 64 × 64, number of slices = 32, transverse orientation, slice thickness = 3.5 mm, 25% distance factor, and total of 210 volumes. During the fMRI scan, the subjects were instructed to relax, remain still and close their eyes.
Resting-state Fmri Data Preprocessing
Resting-state fMRI data were analysed using MATLAB (The Math Works, Natick, MA) software and statistical parametric mapping software (SPM12; http://www.fil.ion.ucl.ac.uk/spm/software/spm12). To avoid scanner instability and to adapt the participants to the noise of the scanner, the first 10 volumes were discarded for each participant. Next, slice timing was performed to correct for intra-volume differences in acquisition time and head motion correction using six-parameter rigid-body linear transformation conducted on the remaining volumes. Then, we set the anterior commissure as the origin on the high-resolution T1-weighted image to co-register the structural image to the mean functional image. The T1 images were then segmented into grey matter, white matter and bias field-corrected structural images. Afterwards, the images were spatially normalized to the standard Montreal Neurological Institute (MNI) stereotaxic space and resampled to 3 × 3 × 3 mm3. Then, spurious signals, including the time series of six head motion parameters and the signal from the white matter and the cerebrospinal fluid, were regressed out using a general linear model, and linear trends were removed from the fMRI data. Finally, spatial smoothing was performed on the functional images using a Gaussian filter (6 mm full-width half-maximum, FWHM).
The head motion parameters of all participants were calculated in the translational and rotational directions (i.e., x, y, z, roll, pitch, and yaw). The participants were excluded if their maximum translation was > 2 mm or if their rotation was > 2o in any direction. Head motion in all directions was compared between groups, and we found that the head motion parameters of the patients with SSD and control groups did not significantly differ (𝑥, 𝑝=0.57; 𝑦, 𝑝=0.29; 𝑧, 𝑝=0.47; pitch, p = 0.14; roll, 𝑝=0.11; yaw, 𝑝=0.30).
Data analysis
ReHo analysis
We used DPABI (Data Processing & Analysis of Brain Imaging) v2.0 to conduct the ReHo based on unsmoothed data [12]. A temporal band-pass filter (0.01 < f < 0.1 Hz) was applied to reduce the influences of low-frequency drift and high-frequency respiratory and cardiac noise.
An individual ReHo map was generated by calculating the concordance of the KCC of the time series of a given voxel with those of its 26 nearest neighbours [7]. To eliminate the effect of individual diversification, the ReHo value of each voxel was converted into a z-score by subtracting the mean ReHo value and dividing the standard deviation of the whole-brain ReHo map. Finally, standardized ReHo maps were spatially smoothed with a 6-mm FWHM Gaussian kernel.
Alff Analysis
The ALFF analysis was the same as in previous studies and was based on preprocessed data. For a given voxel, the time series was transformed to the frequency domain using fast Fourier transforms, and the square root of the power spectrum was calculated and averaged for 0.01–0.1 Hz. This averaged square root was referred to as the ALFF. Finally, the ALFF value of each voxel was converted into a standardized z-score by subtracting the mean ALFF value and dividing the standard deviation of the whole-brain ALFF map so that the maps could be compared across subjects.
Statistical analysis
In this study, we focused only on the significant changes in the sensorimotor network in migraineurs without aura compared to the controls. The maps of the significant differences in ReHo and ALFF of the 45 patients and the 43 controls were compared using voxel-wise two-sample t-tests with age and gender as covariates. To address the issue of multiple comparisons, the ReHo and ALFF statistical maps were assigned thresholds at p < 0.001 (voxel level), and family-wise errors (FWE) were corrected to p < 0.05 at the cluster level. The surviving clusters were reported.