Research Of Neural Mechanism Of Functional Defecation Disorders And Cupuncture Treatment

Functional defecation disorders (FDD) is one category of functional constipations as classified in Rome III Criteria with continued difficulty in defecation,reduced number of bowel movements or feeling of incomplete defecation as the main manifestations. The pathogenesis is not clear. By means of combined electroneurophysiological examination of transcranial stimulation motor-evoked potentials and cerebral evoked potentials, this study investigates the relations between human cerebral cortex and anorectal movements and between the conditions of sensory nerve pathways and conditions of sensory nerve pathways as well as their roles in pathogenesis of FDD. Based on the findings, this paper explores the neural mechanisms of acupuncture treatment of FDD.Objectives:(1) To study transcranial magnetic stimulation cortex motor evoked potentials(TMS-CMEP) and cerebral evoked potentials (CEP) in volunteers, investigate normal human cerebral cortex - anorectal movement and sensory nerve conduction status and determine the laboratory normal range. (2) To analyze and compare the differences between FDD patients and volunteers in TMS-CMEP and CEP and investigate the roles of afferent and efferent nerve pathways in pathogenesis of FDD.(3) To utilize acupuncture to regulate motor and sensory nerve conductions and treat FDD, observe the recent effects,and further investigate the neural mechanisms of acupuncture.Method:(1) In this study,30 cases healthy volunteers were recruited as a control group,including 13 males and 17 females (age 19-35 years,mean age 24.67±7.14 years).All the volunteers were healthy and presented with normal physical examination findings and no gastrointestinal tract dysfunctions. Meanwhile, 60 cases of FDD patients were collected, including 23 males and 37 females (age 23?69 years, mean age 51.12±15.60 years,course 7.58 ± 7.14 years). The patients consisted of 39 cases of unrelaxed pelvic floor constipation and 21 cases of pelvic floor relaxation constipation. All patients were excluded from digestive system and nervous system diseases. Lumbar nerve root stimulation evoked potentials, transcranial magnetic stimulation cortical motor evoked potentials and sensory evoked potentials of healthy volunteers and FDD patients were detected respectively.(2) 30 cases accepted acupuncture treatment voluntarily, including 11 males and 19 females (age 25-65 years,mean age 46.44±11.28 years,course 0.5-24 years). The patients consisted of 23 cases of unrelaxed pelvic floor constipation and 7 cases of pelvic floor relaxation constipation. A questionnaire was filled out and defecation symptoms were systematically scored before the treatment, and then two courses of acupuncture treatment were given. Clinical effects were observed 20d later, and the motor evoked potentials and sensory evoked potentials before and after the treatment were detected.Results:(1) A large positive wave was led out in all the 30 healthy volunteers in the the MS-LMEP examination with an amplitude of 400?1100 u v (mean 725.63±178.23 u v ),a latency of 2.6?3.7ms (mean 3.35 ± 0.41 ms); the positive wave amplitude of TMS-CMEP was 88.9±234.7 u v (mean 193.06 ±79.01 u v),and the latency was 18.3-21.20ms (mean 20.73 ± 2.07ms); the interval between the stimulation and occurrence of P1 wave in the TMS-CMEP examination was 34.5-49.4ms (mean 45.49 ± 4.87 ms); the interval between the stimulation and occurrence of the first positive N1 was 72.3?112.6ms (mean 98.20 ± 21.09 ms); the P1-N1 amplitude was 3?7.7 u v (mean 4.30±1.49 u v) and the P2 latency was 159?254 ms (mean 213.44± 25.08 ms).(2) Compared with healthy volunteers, FDD patients presented with prolonged evoked potential latencies and lowered amplitudes in the MS-LMEP examination of statistic significance (p-values of t-test < 0.05), and the latencies were negatively correlated with the sphincter lengths with a correlation coefficient of -0.354. The results indicated demyelination of motor nerve between the stimulation point (L4 spinal nerve root) and the anal sphincter and reduced nerve conduction velocity. It is inferred that such changes of the peripheral nervous system affect the functions of the pelvic floor under its domination, which may be the pathogenesis of FDD.(3) CMEP was led out in 52 cases in TMS-CMEP examination (86.67%) of the 60 FDD patients and negative in 8 cases (13.33%), of which 3 showed bilateral waveform missing and 5 showed unilateral waveform missing. Compared with the healthy volunteers, the 52 cases of FDD patients presented with lowered amplitudes of statistical significance (P<0.05) and slight prolonged cortex latencies and interspike intervals of no statistical significance (P>0.05) in TMS-CMEP examination. The CMEP latencies of the FDD group were positively correlated with the peak systolic blood pressures (spearman analysis) with a correlation coefficient of 0.421.The CMEP amplitudes were positively correlated with LMEP volatility with a correlation coefficient of 0.331. The above findings indicated that changes had occurred to cortical excitability and subcortical motor nerve pathways and caused dysfunctions to the descending nerve pathways in part of the FDD patients, and the high-level center could not effectively control activities of the low-level center, which was manifested by pelvic floor muscle instability or abnormal contraction and formed the pathophysiological basis of defecation disorders. Such findings also further confirm that the brain - gut axis efferent pathway abnormalities is one of the neural mechanisms of FDD.(4) Compared with healthy volunteers, FDD patients had statistically significantly prolonged P1 and P2 wave latencies (P<0.05) and statistically insignificantly prolonged P1-N1 peak-to-peak amplitudes. These findings indicate that significant pathophysiological changes had occurred to neurotransmission under rectal visceral low-sensitivity status, suggesting that reduced visceral sensitivity and sensory afferent pathway abnormalities may be an important factor of the FDD pathophysiological process and further confirming that the brain - gut axis efferent pathway abnormalities is one of the neural mechanisms of FDD.(5) MS-LMEP, TMS-CMEP and CEP were conducted on the 30 patients before and after the acupuncture treatment. The study revealed that MS-LMEP amplitudes were significantly enhanced (p<0.05); P1 latencies were shortened (p<0.05) while N1 and P2 latencies as well as P1-1 amplitudes were not significantly changed; TMS-CMEP latencies and amplitudes were not significantly changed, either. These findings indicate that acupuncture treatment of constipation mainly works by improving the patients' visceral sensory afferent functions and aims at rectal sensory dysfunctions,the pathophysiological basis of FDD. On the other hand, it has no obvious effects on the cortical excitability and subcortical efferent pathways, but it can improve the conditions of peripheral motor nerve demyelination in FDD patients. These may be one of the virtual neural mechanisms of acupuncture treatment of constipation.Conclusion:Conduction of MS-LMEP, TMS-MEP and CEP neurophysiological examinations in normal persons is relatively easy, laboratory normal data are evenly distributed and reliable, and thus such examination is applicable in clinical diagnosis of related diseases and has clinical promotion value.(2) FDD patients present with peripheral motor nerve demyelination and reduced nerve conduction velocity, which affects the functions of the pelvic floor and is inferred to be the pathogenesis of FDD.(3) Changes occur to cortical excitability and subcortical motor nerve pathways of FDD patients and the dysfunctions of the descending nerve pathways affect the effective control of the high-level center on the activities of the low-level center,which is manifested by pelvic floor muscle instability or abnormal contraction. These findings indicate that the brain - gut axis efferent pathways (motor nerve pathways)abnormalities is one of the neural mechanisms of FDD.(4)Reduced visceral sensitivity may be an important factor of the FDD pathophysiological process, and the brain - gut axis efferent pathway (motor nerve pathways) abnormalities is also one of the neural mechanisms of FDD.(5)cupuncture treatment of constipation mainly works by improving the sensory afferent nerve pathways and has no obvious effects on the subcortical motor efferent nerve pathways.