Study Of Resting-state Spontaneous Brain Activity And Functional Connectivity In Patients With Chronic Low Back Pain Caused By Lumbar Disc Herniation

BackgroundLumbar disc herniation(LDH)refers to a series of symptoms and signs caused by oppression and irritation to nerve root due to fibrous ring rupture and nucleus pulposus herniation.It is an age-related degenerative disease,characterized by rapid onset,long course of disease and easy recurrence in a short time,causing serious damages to the physical and mental health of those patients.This disease is one of the main causes of chronic low back pain(c LBP).Most of the patients show radiation pain in the waist and lower limbs or accompanied by local numbness,abnormal reflex and other symptoms.It is reported that the prevalence of c LBP in adults is as high as 20.3%,which gradually increases linearly after the age of 30,causing a greater burden on personal life and socio-economic conditions.c LBP is the leading cause of limited mobility and disability in patients,and is related to neurodegenerative changes of the brain structure,which can accelerate the aging speed of the brain.c LBP is also a disease related to the human physiology and psychology;however,the underlying mechanisms are not clear.Most patients often accompanied with anxiety,depression and other psychosomatic symptoms,which had a negative impact on treatment efficacy of the disease.Previous neuroimaging studies have shown that the central nervous system is involved in the development,maintenance and experience of chronic pain,and that c LBP can cause extensive structural and functional changes in the brain.However,the researches on the effects of LDH-caused c LBP on the brain function is still limited,especially for the relationships between brain functional changes and clinical symptoms.Therefore,a better understanding of the patterns of change in spontaneous brain activity and whole-brain functional connectivity(FC)in those patients will improve our understanding of the central nervous regulatory mechanisms of c LBP.ObjectivesTo investigate the patterns of changes in spontaneous brain activity and whole-brain FC in patients with c LBP caused by LDH and their relationships with clinical symptoms.MethodsA total of 55 patients with c LBP caused by LDH(c LBP group)and 60 age-,genderand education level-matched healthy volunteers(control group)were included.The resting state f MRI data of all subjects were collected.Firstly,the fractional amplitude of low frequency fluctuation(f ALFF)values were compared between the two groups at the wholebrain level.Then,voxel-wise whole-brain FC analysis was performed with the brain regions showing significant between-group differences in f ALFF as seed points.The visual analogue scale(VAS),Oswestry disability index(ODI)and self-rating depression seale(SDS)were used to evaluate the severity of pain,dysfunction and depression,respectively.Finally,the correlations between the f ALFF and FC values of regions showing significant betweengroup differences and the scale scores were analyzed in patients with c LBP.Results1.Compared with the control group,the c LBP group showed higher f ALFF values in the left orbitofrontal cortex(GRF correction,voxel level P < 0.001,cluster level P < 0.05).There were no regions showing decreased f ALFF values in patients with c LBP compared with control subjects.2.With the left orbitofrontal cortex(OFC)as the region of interest,the whole-brain FC analysis showed that the c LBP group,relative to the control group,exhibited decreased FC between the left OFC and the bilateral precuneus,and increased FC between the left OFC and the left insula,right middle frontal gyrus,and right superior margin gyrus(all GRF correction,voxel level P < 0.001,cluster level P < 0.05).3.The FC value between the left OFC and right middle frontal gyrus was negatively correlated with VAS score in patients with c LBP(r=-0.273,P=0.044).However,the FC values between the left OFC and other brain regions and the f ALFF values in left orbitofrontal cortex showed no significant correlations with the VAS,ODI and SDS scores.ConclusionsIncreased neural activity of the left OFC and its altered FC with precuneus,insula,middle frontal gyrus,and superior marginal gyrus might play an important role in the dysregulation of pain in patients with c LBP,and the OFC-dorsolateral prefrontal cortex circuit might be associated with the severity of pain.