| Background and ObjectivesThe pathogenic mechanism of functional dyspepsia (FD) has not been elucidated well. Heterogeneities in pathophysiological basis may exist among different subtypes. Visceral hypersensitivity is one the most important mechanisms of FD pathogenesis, which is considered to have closer relationship with epigastric pain syndrome (EPS) by some studies. Central nervous system is the center for visceral sensation processing. The regional brain activity of visceral pain neuromatrix has been found different between FD patients and healthy people. This study aims to observe the regional brain activity difference among subtypes of FD, with the blood oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI), and to look into some possible influential factors.Patients and MethodsTwenty-four FD patients, including10EPS,7post-prandial distress (PDS) and7mixed type patients, and10healthy subjects (HS) were enrolled. Every subject was given proximal gastric water load test with pure water of2temperatures (37degree and4degree centigrade), whose regional brain activities during resting state and under water load of different temperatures were observed and compared at the group level. Every FD patient was evaluated on dyspepsia symptoms, anxiety and depression state, social support, illness behavior and gastric motility functions. The correlations between regional brain activity and those indices were then analyzed.Results(1) Differences of resting state regional brain activities between FD and HS were found in limbic lobe (parahippocampal gyri), pallidum, prefrontal cortex, cerebella and pons (P<0.05). EPS showed more significant difference from HS, compared to PDS or mixed type, on limbic systems (including cingulate cortices, parahippocampal gyri, temporal pole) and prefrontal cortex, and involved right insula, left temporal lobe and right occipital lobe as activity difference areas.(2) Comparing the37℃water load task related regional brain activations between FD and HS showed the following difference:lower activations in left limbic lobe (middle cingulate cortex, dorsal posterior cingulate cortex), left middle and inferior temporal gyri (P<0.05), while higher activations in left cerebelllum and vermis, bilateral occipital lobes and right secondary somatosensory cortex (SH)(P<0.05). EPS showed greater difference from HS, compared to PDS or mixed type.(3) Under the4℃water load stimulation, HS showed (de)activations in bilateral limbic system (anterior, middle and posterior cingulate cortices, insula and temporal poles), prefrontal cortices and pons (P<0.05). EPS showed greater response in anterior cingulate cortex and thalamus activation to cold stimulus than37℃water, and this feature of activation difference was more obvious than HS.(4) The dyspepsia symptom score of FD had significant correlations with anterior cingulate cortex, prefrontal cortex, parahippocampal gyrus, temporal pole and superior parietal lobule (P<0.01). The regions with top correlations with various psychosocial scales were found to be right parahippocampal gyrus, inferior temporal gyrus, superior frontal gyrus, cerebellar crus, and left angular gyrus and inferior frontal gyrus (.R>0.684, P<0.01). Concerning the gastric motility functions, left inferior temporal gyrus, right middle frontal gyrus and left superior frontal gyrus showed good correlations with maximal perfusion volume, proximal intragastric pressure change and proximal gastric compliance, respectively.ConclusionsThe regional brain activity of FD is significantly different from HS, both during the resting state and under water perfusion stimulus of different temperatures. The difference could be influenced by symptom severity, psychosocial factors, and gastrointestinal motility. When comparing FD subtypes with HS, EPS showed greater difference than PDS, which may indicates that the abnormality of pain processing by central nervous system is the main pathogenic mechanism of EPS. |
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