Research On Cortical Reorganization Following Hypoglossal-Facial Nerve Neurorrhaphy By Task Functional Magnetic Resonance Imaging

Part One Cortical representation sites of facial and tongue movements: a task functional magnetic resonance imaging studyObjective Investigating the identical and prior representation sites of facial and tongue movements by task functional magnetic resonance imaging study.Methods Twenty right-handed healthy subjects underwent block-design task functional magnetic resonance imaging examination. Oral-facial movements included eye blinking, lip pursing, gas drum, teeth grinning, vertical tongue excursion. Participants were asked to keep relax or execute certain tasks by following the instruction presented on the projector. In each task, after a 8s rest period, 6 blocks with 40 s duration were run continually, each block consists of 20 s constant pace with a frequency of 1Hz, then followed by a 20 s rest. During the rest block, the participants were instructed to relax. To demonstrate the identical activation clusters of cerebral cortex during facial and tongue movements, the one-sample t-test was employed. To test the differences in activated cortex clusters between facial movements and tongue movement, a paired t-test statistic algorithm were applied between each group of facial movements and tongue movement(eye blinking and vertical tongue excursion,lip pursing and vertical tongue excursion, gas drum and vertical tongue excursion, teeth grinning and vertical tongue excursion). The result were visualized on Xjview, with threshold P=0.01(false discovery rate corrected, FDR corrected). The t-maps were then overlaid on MNI template.Results The identical activated cortexes in oral-facial movements included bilateral cerebellum, bilateral insula, bilateral SMC, bilateral SMA, bilateral CMA, bilateral angular gyrus, bilateral supra-marginal gyrus and bilateral basal ganglia. Paired T-test showed prior activation of vertical tongue excursion was found in bilateral insula, bilateral SMA compared with eye blinking; while prior activation of eye blinking was found in bilateral calcarine sulcus, bilateral cuneus, bilateral lingualis gyrus, right inferior parietal lobe and left precentral gyrus compared with vertical tongue excursion. Prior activation of vertical tongue excursion was found in bilateral SMC, bilateral SMA and left superior parietal lobe compared with lip pursing. Prior activation of vertical tongue excursion was found in left postcentral gyrus compared with gas drum; while prior activation of gas drum was found in bilateral precentral gyrus, bilateral cuneus compared with vertical tongue excursion. Prior activation of vertical tongue excursion was found in bilateral SMC compared with teeth grinning; while prior activation of teeth grinning was found in bilateral cuneus, bilateral SMC compared with vertical tongue excursion.Conclusion The identical representation sites suggests the identical activation pathway between facial and tongue movements. And some brain areas could be considered as the prior activation representation in facial movements compared with tongue movement.Part Two Time-course of changes in activation among facial nerve injuryObjective Patients suffering different intervals of facial nerve injury were investigated by functional magnetic resonance imaging to study time course of changes in activation within cortex.Methods Forty-five patients were divided into three groups based on intervals of facial nerve injury: facial nerve injury lasting less than 6 months(n = 15); facial nerve injury lasting more than 6 months and less than 1 year(n = 15); facial nerve injury lasting more than 1 year and less than 2 years(n = 15). Another sixteen age and gender matched healthy participants were included as a control group. Patients and healthy participants underwent block-design task functional magnetic resonance imaging examination. Task movements included eye blinking and lip pursing. Participants were asked to keep relax or execute certain tasks by following the instruction presented on the projector. In each task, after a 8s rest period, 6 blocks with 40 s duration were run continually, each block consists of 20 s constant pace with a frequency of 1Hz, then followed by a 20 s rest. During the rest block, the participants were instructed to relax. Two sample T-tests were used to test for areas of increased or decreased activation in the three facial nerve injury groups relative to the normal healthy group. The result were visualized on Xjview, with threshold P=0.01(false discovery rate corrected, FDR corrected). Correlation analysis between the activation intensity in sensorimotor area of lip pursing task results and the intervals of facial nerve injury was calculated. The activation intensity in sensorimotor area was represented by Z value in SPM8, for FWE(family-wise error) corrected value of P= 0.05. In addition, curve fitting between the Z value in sensorimotor area in lip pursing task results and the intervals of facial nerve injury was also shown, with a threshold alpha value of P< 0.05, SPSS v.17.0 statistical software program.Results For the facial nerve injury lasting less than 6 months, increased activation in bilateral postcentral gyrus and bilateral inferior parietal lobe was detected in the eye blinking task results as compared with the healthy control group and increased activation in bilateral precuneus lobe was observed in the lip pursing task results as compared with the healthy control group. For the facial nerve injury lasting more than 6 months and less than 1 year, increased activation in right supra-marginal gyrus was detected in both the eye blinking and lip pursing task results as compared with the healthy control group. For the facial nerve injury lasting more than 1 year and less than 2 years, decreased activation in left sensorimotor area was observed in the lip pursing task results as compared with the healthy control group. Significant correlation was found between Z value in left sensorimotor area in lip pursing task results and intervals of facial nerve injury, with Pearson’s correlation coefficient-0.951(P<0.001). The fitted regression equation between Z value in left sensorimotor area(Y) and intervals of facial nerve injury(X) was as following: Y=10.086-0.463X(P<0.001, R2=90.5%, N=45). Significant correlation was detected between Z value in right sensorimotor area in lip pursing task results and intervals of facial nerve injury, with Pearson’s correlation coefficient 0.333(P=0.025). The fitted regression equation between Z value in right sensorimotor area(Y) and intervals of facial nerve injury(X) was as following: Y=12.063-1.29X+0.139X2-0.004X3(P<0.001, R2=64.1%, N=45).Conclusion Increased activation in integration areas, such as supra-marginal gyrus and precunes lobe, could be detected in the early-middle stage of facial dysfunction compared with normal subjects. Decreased activation in sensorimotor area contra-lateral to facial nerve injury could be found in late stage of facial dysfunction compared with normal subjects. Dysfunction in facial nerve has devastating effects on the activity of sensorimotor areas, while enhanced intensity in the sensorimotor area ipsilateral to facial nerve injury in middle stage of facial dysfunction suggests the possible involvement of inter-hemispheric reorganization. Behavioural or brain stimulation techniques treatment in this stage could be applied to alter reorganization within sensorimotor area in the rehabilitation of facial function and improvement in therapeutic intervention along the course of recovery.Part Three Functional imaging study about reorganization following hypoglossal-facial nerve ‘side’-to- side neurorrhaphy in facial nerve injuryObjective Investigate the brain reorganization following hypoglossal-facial nerve ‘side’-to- side neurorrhaphy and the correlation between brain reorganization and House-Brackmann score(HBS) following neurorrhaphy.Methods Thirty-two patients with right facial nerve injury were performed hypoglossal-facial nerve ‘side’-to- side neurorrhaphy. Task functional magnetic resonance imaging was required before and after neurorrhaphy at 3 and 6 months later. Two tasks, eye blinking and lip pursing were involved in the functional magnetic resonance imaging examination. Paired t-test was used to indicate the reorganization following neurorrhaphy at a threshold false discovery rate corrected value of P= 0.01. Correlation analysis between intensity in sensorimotor area in lip pursing task results and HBS after neurorrhaphy 6 months later was also inquired. The activation intensity in sensorimotor area was represented by Z value in SPM8, for FWE(family-wise error) corrected value of P= 0.05. In addition, curve fitting between the Z value in sensorimotor area in lip pursing task results and HBS after neurorrhaphy 6 months later was also shown, with a threshold alpha value of P< 0.05, SPSS v.17.0 statistical software program.Results Changes of HBS could be detected 6 months later after neurorrhaphy. Paired t-test showed increased activation in right angular gyrus could be found at 3 moths later following neurorrhaphy and increased activation in left superior parietal lobule, left postcentral gyrus could be found at 6 months later following neurorrhaphy, compared with the same patients before neurorrhaphy(FDR, P=0.01). There was no differences in activation before and after neurorrhaphy in the eye blinking task results(FDR, P=0.01). In lip pursing task results, significant correlation was found between Z value in left sensorimotor area and the HBS 6 months following neurorrhaphy, with Pearson’s correlation coefficient-0.917(P<0.001). The fitted regression equation between Z value in left sensorimotor area(Y) and HBS 6 months following neurorrhaphy(X) was as following: Y=32.306-14.768X+3.702X2-0.334X3(P<0.001, R2=93.1%, N=32). Positive correlation was detected between changes in Z value(ΔZ value) within left sensorimotor area and changes in the HBS(ΔHBS) before and 6 months following neurorrhaphy, with Pearson’s correlation coefficient 0.881(P<0.001). The fitted regression equation between changes in Z value in left sensorimotor area(Y) and changes in HBS 6 months before and 6 months following neurorrhaphy(X) was as following: Y=0.81-1.52X+2.424X2-0.482X3(P<0.001, R2=84.2%, N=32).Conclusion Functional reorganization could be found 3 months later following neurorrhaphy although clinical improvement could be acquired 6 months later following neurorrhaphy. Functional reorganization following neurorrhaphy could be identified as positive physiological reactions to promote the facial nerve rehabilitation. More increased in Z value within left sensorimotor area in lip pursing task results 6 months later following neurorrhaphy imply more increased in facial nerve rehabilitation and more decreased in HBS. Z value within left sensorimotor area in lip pursing task results 6 months later following neurorrhaphy could also be served as an objective reference to estimate the rehabilitation of facial nerve.Part Four Differences in reorganization following hypoglossal-facial nerve ‘side’-to- side neurorrhaphy among different prognosis in facial nerve injuryObjective Investigate the differences in reorganization following hypoglossal-facial nerve ‘side’-to- side neurorrhaphy among different prognosis in facial nerve injuryMethods Thirty-two patients with right facial nerve injury were performed hypoglossal-facial nerve ‘side’-to- side neurorrhaphy. Task functional magnetic resonance imaging was required before and after neurorrhaphy at 3 and 6 months later. Two tasks, lip pursing and vertical tongue excursion were involved in the functional magnetic resonance imaging examination. Patients were divided into two groups according to the changes in HBS before and after neurorrhaphy: reduction in HBS of more than or equal to two levels(ΔHBS≥2), called for Group A; reduction in HBS of less than two levels(ΔHBS <2), called for Group B. Two sample T-tests were used to test for areas of increased or decreased activation in patients from Group A relative to patients from Group B before and after neurorrhaphy at 3 and 6 months later. The result were visualized on Xjview, with threshold P=0.01(false discovery rate corrected, FDR corrected). The activation intensity and the activation voxel in sensorimotor area in two tasks were represented by Z value and V value in SPM8 respectively before and after neurorrhaphy at 3 and 6 months later, for FWE(family-wise error) corrected value of P= 0.05. Two sample T-tests were used to test for Z value and V value in patients from Group A relative to patients from Group B before and after neurorrhaphy at 3 and 6 months later in two tasks, with a threshold alpha value of P< 0.05, SPSS v.17.0 statistical software program.Results Fifteen cases showed reduction in HBS of more than or equal to two levels(ΔHBS≥2), called for Group A. Another seventeen patients showed reduction in HBS of less than two levels(ΔHBS <2), called for Group B. Two sample t-test showed that increased activation in left sensorimotor area and increased activation in left postcentral gyrus and left inferior parietal lobule could be found at 3 moths later following neurorrhaphy and increased activation in left sensorimotor area, left inferior parietal lobule and right supra-marginal gyrus could be found at 6 moths later following neurorrhaphy in patients from Group A relative to the patients from Group B in lip pursing task results(FDR, P=0.01). Increased in Z value and V value within left sensorimotor area in lip pursing task results 6 moths later following neurorrhaphy could be found relative to before and 3 moths later following neurorrhaphy(P< 0.05); patients from Group A had increased Z value and V value within left sensorimotor area in lip pursing task results relative to patients from Group B(P< 0.05). Decreased in V value within left sensorimotor area in vertical tongue excursion task results 6 moths later following neurorrhaphy could be found relative to before and 3 moths later following neurorrhaphy(P< 0.05); patients from Group A had decreased V value within left sensorimotor area in vertical tongue excursion task results relative to patients from Group B(P< 0.05). Patients from Group A had more increased in changes in Z value(ΔZ) and V value(ΔV) than patients from Group B in lip pursing task results before and 6 moths later following neurorrhaphy(P< 0.05).Conclusion Activation intensity within sensorimotor area contralateral to facial nerve injury might be related to the clinical promotion before and after neurorrhaphy. Involvement of integration in sensorimotor information and supra-motor model contralateral to facial nerve injury could promote the rehabilitation of facial function following neurorrhaphy. Functional transform from tongue movement to facial movement within sensorimotor area might be responsible for the obvious clinical rehabilitation following neurorrhaphy.