| Objective:To study the changes of cerebral structure in patients of obstructive sleep apnea syndrome (OSAS) by using voxel-based morphometry (VBM), ADC map and magnetic resonance spectroscopy (MRS).Materials and methods:21 severe OSAS (AHI> 40/h) patients,14 mild-moderate OSAS (5/h<AHI< 40/h) patients, and 15 healthy control subjects (AHI< 5/h) were included. All people were scaning buy 1.5Tesla Marconi Medical System (Eclipse).Scanning parameter:1.T1 WI-RF-FAST sequence (TR/TE=12 ms/4.5ms, FOV 25 cm2, thickness 1.2 mm, interval 0m, matrix 256*256, FLIP 20°). VBM was calculated on SPM5 (statistic parameter mapping 5).2.SE-EPI-DWI (TR/TE=6000 ms/94.9 ms, thickness 5.0 mm, interval 1 mm, matrix 100x100, FLIP 90°, b=1000 s/mm2). All the ADC maps were calculated on SPM5.3. the MRS by using the point-resolved echo spin spectroscopy (PRESS) (TR/TE=1500ms/35ms, FLIP 90°). Proton volumes of interest (VOIs) were placed in the bilateral frontal lobes and left temporal-parietal-occipital cortex.(VOI:20mmx20mm><20mm), left hippocampus(VOI:15mmxl5mmx20mm). NAA, Cho, Mi, Glx/Gln were calculated.Results:l.VBM showed:(1)The bulk volume of gray matter (GM) showed decreased in OSAS patients. It indicated changes of GM was more sensitive than other structure. (2)In separate encephalic region:?The density and volume of GM in OSAS patients reduced compared to the control group.In the mild-moderate OSAS group, the density and volume of GM reduced could be related to neural loss, only. In the severe OSAS group, the reduced density and volume of GM could be related to neural loss and reactive gliosis.?There was increased in the density and volume of white matter (WM) in OSAS patients, the mild-moderate OSAS group was higher than the severe OSAS group. Increase in the density and volume of WM could be interpreted as hyperplasia. Decrease in the density and volume of WM in the severe OSAS group could be interpreted as evidence of WM rarefaction, respectively, secondary to repeated episodes of hypoxia in OSAS.2.ADC map showed:(1)The increase of ADC value was seen mostly in GM in the mild-moderate OSAS group. It was corresponded with VBM, which had neural loss only at this time. (2)The increase of ADC value was found in GM and WM in the severe OSAS group. The changes was mainly located in right frontal lobe, left precuneus, both side of anterior lobe of cerebellum, and right occipital forceps. The manifestation was accorded with neural loss and reactive gliosis in GM,and rarefaction in WM.3. Changes in the brain stem was detected on both ADC map and VBM, indicating microstructural pathology.3. (1)Significantly lower values of the N-acetylaspartate (NAA)/creatine (Cr) ratio (F=6.003, p=0.004) was found in left frontal lobe in the severe OSAS group compared to controls. In the right frontal lobe, NAA/Cr X2=11.677,P=0.003) ratio was also showed reduced in the OSAS patients. The apparence could be related to neural loss. (2)A significant increase in the myo-inositol (mI)/Cr ratio X2=16.518, p=0.000) was evident in right frontal regions. It could be interpreted as evidence of reactive gliosis, consequent to repeated episodes of hypoxia in OSAS. (3)Glutamine-glutamite (Glx/Gln)/Cr ratio (F=4.381, p=0.019) values were also significantly smaller in left frontal regions. It was coincidence with clinical apparence.Conclusion:. VBM, ADC map and MRS were sensitive in evaluating cerebral structural changes in OSAS patients. |
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