title: The side of chronic low back pain matters: evidence from the primary motor cortex excitability and the postural adjustments of multifidi muscles.
abstract: Hemispheric lateralization of pain processing was reported with overactivation of the right frontal lobe. Specifically in chronic low back pain (CLBP), functional changes in the left primary motor cortex (M1) with impaired anticipatory postural activation (APA) of trunk muscles have been observed. Given the connections between frontal and M1 areas for motor planning, it is hypothesized that the pain side could differently influence M1 function and APA of paravertebral multifidus (MF) muscles. This study aimed at testing whether people with right- versus left-sided CLBP showed different M1 excitability and APA. Thirty-five individuals with lateralized CLBP (19 right-sided and 16 left-sided) and 13 pain-free subjects (normative values) were tested for the excitability of MF M1 area (active motor threshold-AMT) with transcranial magnetic stimulation and for the latency of MF APA during bilateral shoulder flexion and during unilateral hip extension in prone lying. In the right-sided CLBP group, the AMT of both M1 areas was lower than in the left-sided group and the pain-free subjects; the latency of MF APA was shorter in bilateral shoulder flexion and in the left hip extension tasks as compared to the left-sided group. In CLBP, an earlier MF APA was correlated with lower AMT in both tasks. People with right-sided CLBP presented with increased M1 excitability in both hemispheres and earlier MF APA. These results likely rely on cortical motor adaptation related to the tasks and axial muscles tested. Future studies should investigate whether CLBP side-related differences have a clinical impact, e.g. in diagnosis and intervention.
authors.affiliation: Laboratory of Clinical Neuroscience and Neurostimulation, Neuroscience Division of the Centre de recherche du CHU de Québec, RC-9800, 2705 Blvd. Laurier, Quebec City, QC, G1V 4G2, Canada.|Constance Lethbridge Rehabilitation Center Research Site of the CRIR, Montreal, QC, Canada.
authors.forename: Hugo
authors.initials: H
authors.lastname: Massé-Alarie
authors.affiliation: Laboratory of Clinical Neuroscience and Neurostimulation, Neuroscience Division of the Centre de recherche du CHU de Québec, RC-9800, 2705 Blvd. Laurier, Quebec City, QC, G1V 4G2, Canada.
authors.forename: Louis-David
authors.initials: LD
authors.lastname: Beaulieu
authors.affiliation: Constance Lethbridge Rehabilitation Center Research Site of the CRIR, Montreal, QC, Canada.|School of Physical and Occupational Therapy, McGill University, Montreal, QC, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Preuss
authors.affiliation: Laboratory of Clinical Neuroscience and Neurostimulation, Neuroscience Division of the Centre de recherche du CHU de Québec, RC-9800, 2705 Blvd. Laurier, Quebec City, QC, G1V 4G2, Canada. cyril.schneider@rea.ulaval.ca.|Department of Rehabilitation, Faculty of Medicine, Université Laval, Quebec City, QC, Canada. cyril.schneider@rea.ulaval.ca.
authors.forename: Cyril
authors.identifier: 0000-0002-2179-0481
authors.initials: C
authors.lastname: Schneider
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002908:Chronic Disease; D004185:Disability Evaluation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D015444:Exercise; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D017116:Low Back Pain / Q000473:pathology* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D010147:Pain Measurement; D011187:Posture / Q000502:physiology*; D011795:Surveys and Questionnaires; D050781:Transcranial Magnetic Stimulation
keywords: Anticipatory postural adjustment; Chronic low back pain; Excitability; Motor planning; Pain lateralization; Plasticity; Primary motor cortex