The clinical application of surface electromyography as an objective measure of change in the chiropractic assessment of patient progress: a pilot study
Kelly, S., & Boone, W. R. (1998)
Journal of Vertebral Subluxation Research, 2, 175-181
A pilot study was conducted to evaluate the application of sEMG, as recorded with the Insight 7000 TM Subluxation Station, to the chiropractic clinical setting as an objective measure of change in assessing patient progress. The study revealed that intra-examiner reliability could be demonstrated through a paired two-tailed t-test which takes variation into consideration, rather than using correlation coefficients which could mask examiner error. Thirty patients under the care of 19 different supervised interns in a clinical teaching setting, were, over a four week period, administered a wide range of adjustments in accordance with a planned regimen of care. Findings revealed that all patients experienced a gradual to significant decline in sEMG activity in either the right and/or left side, in 14 of the 15 paraspinal muscular segments evaluated. This suggested a long term effect in sEMG activity changes, as opposed to a short term physiological response. Additional study is underway to evaluate inter-examiner reliability of the Insight 7000 Subluxation Station in the clinical teaching setting. Investigation is also planned to couple sEMG changes to other physical finding. This level of study is expected to contribute to an understanding of the clinical significance of the effects of the chiropractic adjustment on paraspinal muscular activity.
Key Words: Surface electromyography, EMG, sEMG, Insight 7000 Subluxation Station, muscle activity, vertebral subluxation, chiropractic clinical practice.
A longitudinal assessment of chiropractic care using a survey of self-rated health wellness & quality of life: a preliminary study
Marino, M. J., & Langrell, P. M. (1999)
Journal of Vertebral Subluxation Research, 3, 65-73
This longitudinal study evaluated changes in self-rated health status of patients receiving chiropractic care at the training clinic of the New Zealand School of Chiropractic. The study was designed to assess subluxation-based chiropractic care in association with changes in patients’ perceived health status. The Self-Rated Health/Wellness Survey (SRHW) was used to evaluate the health status on two occasions, “initial” and “follow-up.” The instrument assessed health across four domains, Physical State, Emotional/Mental State, Stress and Life Enjoyment. Collectively, these four domains, assessed initially and after a follow-up period, constituted Combined Wellness, or a fifth domain. Quality of Life was evaluated as a sixth domain of the questionnaire instrument. The study population included 89 subjects, evaluated over a five-month study period. The average interval between initial and follow-up surveys was 8.0 ± 3.2 weeks, with an average number of visits of 9.1 ± 4.2. A bivariate analysis was conducted using a two tailed, paired sample t-test to assess the subjects’ survey responses. Subjects reported significant positive perceived changes in Physical State (p = 0.000), Mental/Emotional State (p = 0.008), and Combined Wellness (p = 0.001), with corresponding effect sizes of 0.61, 0.24 and 0.31 respectively. The improvement in the Physical and Mental/Emotional State, and Combined Wellness suggests that chiropractic care provided through the NZ School of Chiropractic is associated with significant benefits in these domains. Study data suggested that health/wellness may accrue with time under care. Thus, further study with a larger sample size and longer duration of care is proposed to more thoroughly investigate possible health benefits in the areas studied, as well as to confirm present findings.
Key words: chiropractic, vertebral subluxation, outcomes assessment, wellness, quality of life, subluxation-based chiropractic, Self-Rated Health/Wellness Survey (SRHW).
Manual Muscle Testing combined with Sepcific Head Positioning, and other Articular Challenges, as an Assessment of Vertebral Subluxation of the Upper Cervical Spine: A Descriptive Paper
Dobson, G. J. (1999)
Journal of Vertebral Subluxation Research, 3, 58-64
This article presents the Dobson Muscle Testing (DMT) procedure. Those aspects of the procedure as it relates to other indicators of vertebral subluxation and other methodologies are described. The procedure detects abberant cervical joint dynamics (movement) through muscle challenges used in combination with various head positions, designed to functionally engage specific articular levels, (positioning) and other articular challenges. In the cervical spine joints and soft tissue there are a large number of mechanoreceptors. Thus, it is postulated that in the presence of vertebral subluxation, when abberant joint mechanics affect these mechanoreceptors, the application of the head postioning challenges produces a barrage of noxious or inappropriate impulses through the cerebellovestibular regulatory circuits. This is believed to result in poor quality motor responses, which may be detected with the DMT procedure through manual muscle testing. The DMT procedure is described as a complement to other forms of vertebral subluxation assessment. To date, clinical observations suggest a positive correlation to Blair upper cervical radiographic analysis in addition to other indicators including muscle and motion palpation and leg length analysis. Further study is planned to test the validity of these observations through controlled studies.
Key Words: Vertebral subluxation, manual muscle testing, Dobson muscle testing protocol, upper cervical spine, applied kinesiology, biomechanics.
Cervical angles in sleep apnea patients: a retrospective study
Dobson, G. J., Blanks, R. H. I., Boone, W. R., & McCoy, H. (1999)
Journal of Vertebral Subluxation Research, 3, 9-23.
The present study was undertaken to evaluate, retrospectively, radiographs from diagnosed Obstructive Sleep Apnea Syndrome (OSAS) patients. Four angles were assessed from the lateral radiographs: (1) atlas/axis, (2) atlas, (3) atlas/occiput, and (4) occiput, which, like the atlas angle, was determined relative to the horizontal plane of the x-ray film. The severity of OSAS was determined by two indices. The first, the standard “Respiratory Disturbance Index” (RDI), indicates the number of apneas and hypopneas per hour of sleep. The second index of OSAS severity, the combined “Sleep Baseline Score” (SBS), was derived from multivariate analysis of a wide variety of sleep parameters. These data were studied through bivariate and multiple regression analyses relative to the level of OSAS severity, sex, and age. Findings suggested that a general kyphotic configuration of the occiput and upper cervical spine existed among the overwhelming majority of OSAS patients. Moreover, data revealed that the greatest extent of flexion was apparent in the most severe OSAS patients, followed by the least severe, and then by the female OSAS patients. Sex differences relevant to the occiput and other upper cervical angles were interpreted cautiously due to the low number of females in the present study, which is characteristic of OSAS patients in general. From the present findings, it is apparent that OSAS patients can be expected to exhibit an upper cervical kyphotic spine. The impact of these findings, and ramifications of OSAS as a somatovisceral model evaluating the effects of chiropractic care are discussed.
Key Words: Sleep apnea, respiratory disturbance index, atlas angle, atlas-axis angle, atlas-occiput angle, sleep baseline score, vertebral subluxation
Use of a mental rotation reaction-time paradigm to measure the effects of upper cervical adjustments on cortical processing: a pilot study
Kellya, D. D., Murphy, B. A., & Backhouse, D. P. (2000)
Journal of manipulative and physiological therapeutics, 23(4), 246-251.
Objectives: To investigate the potential usefulness of a mental rotation paradigm in providing an objective measure of spinal manipulative therapy. To determine if cortical processing, as indicated by response time to a mental rotation reaction-time task, is altered by an upper cervical toggle recoil adjustment. Design: Prospective, double-blind, randomized, controlled trial.
Setting: Chiropractic college clinical training facility.
Participants: Thirty-six chiropractic student volunteers with clinical evidence of upper cervical joint dysfunction.
Intervention: Participants in the experimental group received a high-velocity, low-amplitude upper cervical adjustment. A non-intervention group was used to control for improvement in the mental rotation task as a result of practice effects.
Outcome measures: Reaction time was measured for randomly varying angular orientations of an object appearing either as normal or mirror-reversed on a computer screen.
Results: The average decrease in mental rotation reaction time for the experimental group was 98 ms, a 14.9% improvement, whereas the average decrease in mental rotation reaction time for the control group was 58 ms, an 8.0 improvement. The difference scores after the intervention time were significantly greater for the experimental group compared with the control group, as indicated by a one-tailed, 2-sample, equal variance Student t test, (P < 05).
Conclusion: The results of this study have demonstrated a significant improvement in a complex reaction-time task after an upper cervical adjustment. These results provide evidence that upper cervical adjustment may affect cortical processing.
Keywords: Chiropractic; Manipulation; Mental Rotation; Reaction Time; Cerebral Dysfunction; Cervical Spine Dysfunction
Rapid reversible changes to multiple levels of the human somatosensory system following the cessation of repetitive contractions: a somatosensory evoked potential study
Murphy, B. A., Taylor, H. H., Wilson, S. A., Oliphant, G., & Mathers, K. M. (2003)
Clinical neurophysiology, 114(8), 1531-1537.
Objective: Numerous somatosensory evoked potential (SEP) studies have provided clear evidence that during repetitive voluntary movement, the transmission of somatosensory afferent information is attenuated. The objective of this work was to determine if this gating phenomenon could persist beyond the period of repetitive movement.
Methods: We recorded spinal, brainstem, and cortical SEPs to median nerve stimulation before and immediately after a modified 20 min repetitive typing task that did not involve the thenar muscles.
Results: There were significant decreases in pre-central cortical and subcortical SEP amplitudes for several minutes following task cessation.
Conclusions: These results demonstrate the persistence of the gating phenomenon beyond the cessation of the actual repetitive movement. They also indicate that plastic changes do occur in cortical and subcortical components of the somatosensory system, following voluntary repetitive contractions.
Significance: The persistence of changes in somatosensory processing beyond the period of repetitive activity may be relevant to the initiation of overuse injuries.
Keywords: Somatosensory evoked potentials; Brain plasticity; Repetitive muscular activity; Somatosensory system; Human
Changes in median nerve somatosensory transmission and motor output following transient deafferentation of the radial nerve in humans
Murphy, B. A., Taylor, H. H., Wilson, S. A., Knight, J. A., Mathers, K. M., & Schug, S. (2003)
Clinical neurophysiology, 114(8), 1477-1488.
Objective: To determine if transient anaesthetic deafferentation of the radial nerve would lead to alterations in processing of early somatosensory evoked potentials (SEPs) from the median nerve or alter cortico-motor output to the median nerve innervated abductor pollicis brevis (APB) muscle.
Methods: Spinal, brainstem, and cortical SEPs to median nerve stimulation were recorded before, during and after ipsilateral radial nerve block with local anaesthesia. Motor evoked potentials (MEPs) and motor cortex output maps were recorded from the APB muscle.
Results: There were no significant changes to most early SEP peaks. The N30 peak, however, showed a significant increase in amplitude, which remained elevated throughout the anaesthetic period, returning to baseline once the anaesthetic had completely worn off. MEP amplitude of the median nerve innervated APB muscle was significantly decreased during the radial nerve blockade. There was also a significant alteration in the APB optimal site location, and a small but significant decrease in the silent period during the radial nerve blockade.
Conclusions: Transient anaesthetic deafferentation of the radial nerve at the elbow leads to a rapid modulation of cortical processing of median nerve input and output. These changes suggest an overall decrease in motor cortex output to a median nerve innervated muscle not affected by the radial nerve block, occurring concomitantly with an increased amplitude of the median nerve generated N30 SEP peak, thought to represent processing in the supplementary motor area (SMA). Independent subcortical connections to the SMA are thought to contribute to the N30 response observed in this study. Unmasking of pre-existing but latent cortico-cortical and/or thalamo-cortical connections may be the mechanism underlying the cortical SEP increases observed following radial nerve deafferentation.
Significance: Transient deafferentation of the radial nerve, which supplies wrist and hand extensor muscles, has been shown to alter sensory processing from and motor output to the median nerve innervated thenar muscles.
Abdominal aortic aneurysm: an illustrated narrative review
Crawford, C. M., Hurtgen-Grace, K., Talarico, E., & Marley, J. (2003)
Journal of manipulative and physiological therapeutics, 26(3), 184-195.
Objective: To present a descriptive review of abdominal aortic aneurysm (AAA), including a review of risk factors for and case finding in AAA for chiropractors as primary contact health care practitioners.
Data sources: Clinical and scientific literature identified through various sources including MEDLINE and citation tracking.
Data synthesis: Selective narrative review of relevant literature.
Results: AAA may be asymptomatic; however, back pain is a common presenting feature. Risk factors include male gender, increasing age, cigarette smoking, hypertension, chronic obstructive airway disease, claudication, and AAA in a first-degree relative. AAA should be considered in the differential diagnosis of older white patients, especially males, with low back pain. Estimated prevalence for AAAs in older males is in the order of 3% to 5%; rupture accounts for 1.7% of deaths in men aged 65 to 75 years. Elective surgical resection of AAAs (prior to rupture) offers a low operative mortality and good prognosis.
Conclusion: AAA should be considered in the differential diagnosis of older patients presenting with low back pain and those with risk factors for AAA. Chiropractors, as primary contact health care practitioners, have a responsibility to refer patients suspected of having AAA for appropriate imaging and, where indicated, vascular surgical opinion.
Radiographic anomalies that may alter chiropractic intervention strategies found in a New Zealand population
Beck, R. W., Holt, K. R., Fox, M. A., & Hurtgen-Grace, K. L. (2004)
Journal of manipulative and physiological therapeutics, 27(9), 554-559.
Objective: To provide occurrence rates for anomalies discovered on radiographs in patients seeking chiropractic care.
Methods: One thousand four random patient files dated between 1997 and 2001 were obtained from the records of the outpatient clinic at the New Zealand College of Chiropractic. In cases in which radiographs were taken, the radiographic reports were analyzed by the authors for the presence of a number of anomalies.
Results: Eight hundred forty-seven full-spine radiographs were included in the study. Anomalies were found in 68% of patients who had radiographs taken. The 5 most frequently occurring anomalies in descending order were degenerative joint disease (23.8%), posterior ponticle (13.6%), soft tissue abnormalities (13.5%), transitional segments (9.8%), and spondylolisthesis (7.8%). Other noteworthy occurrences because of their generalized status as absolute contraindications to adjustment are fracture (6.6%), malignant tumor (0.8%-3.1%), abdominal aortic aneurysm (0.8%) and atlantoaxial instability (0.6%).
Conclusion: A large percentage of patients presenting for chiropractic care have anomalies present on spinal radiographs. Further research and analysis is necessary to investigate the risk-verses-benefit ratio of spinal radiographs for chiropractic patients.
Key Indexing Terms: Chiropractic; Radiography; Anomaly; Bone Diseases
The relationship between spinal dysfunction and reaction time measures
Lersa, L. B., Stinear, C. M., & Lersa, R. A. (2005)
Journal of manipulative and physiological therapeutics, 28(7), 502-507.
Objective: The objective of this study was to investigate the relationship between the number of sites of spinal dysfunction and a range of measures of cognitive processing.
Methods: This double-blind, randomized, observational pilot study was performed at a chiropractic college clinical training facility. Thirty volunteers with clinical evidence of cervical spinal joint dysfunction participated. Subjects were classified into 2 groups depending on whether they exhibited signs of cervical spinal joint dysfunction at one or more sites. A range of computer-based tasks was used to determine simple reaction time (RT), choice RT, probe RT, and inhibition of a preplanned response.
Results: Multiple sites of cervical spinal joint dysfunction were related to impaired cortical processing as revealed by significantly higher loads on central capacity, significantly less accurate response selection, and a trend toward more variable performance of an anticipated response. Multiple sites of cervical spinal joint dysfunction do not appear to be related to the speed of response selection or the ability to inhibit a preplanned response.
Conclusion: This pilot study provides a context for the improvements in cortical processing observed after cervical spine adjustment. It shows that probe RT may be a useful tool in further studies examining the effects of cervical spine manipulation of joint dysfunction and the associated effect on cognitive function.
Key Indexing Terms: Cervical Vertebrae; Reaction Time; Spine; Mental Processes; Joint Dysfunction
Chiropractic patients presenting to the New Zealand College of Chiropractic teaching clinic: A short description of patients and patient complaints
Holt, K. R., & Beck, R. W. (2005)
Chiropr J Aust; 35:122-4.
Objective: To report the basic characteristics of new chiropractic patients presenting to the New Zealand College of Chiropractic teaching clinic.
Design and Outcome Variables: Retrospective analysis of 1,004 new patient files opened between 1997 and 2001. Age, gender and chief complaint were recorded.
Results: Some 51.9% of patients were female. The mean age was 32.3 years, and age range was 0-85 years. The most common chief complaint was low back pain (38.1%). Overall spinal problems accounted for 64.4% of chief complaints, and 11.6% of patients presented for wellness care with no complaint present.
Conclusion: Patients presenting to the New Zealand College of Chiropractic teaching clinic showed many similarities with teaching clinics in the United States of America and Australia. Some discrepancies were noted, however, between the patient characteristics at the teaching clinic and the general New Zealand population.
Physical, physiological, and immune status changes, coupled with self-perceptions of health and quality of life, in subjects receiving chiropractic care: a pilot study
Boone, W. R., Oswald, P., Holt, K., Beck, R., Singh, K., & Ashton, A. (2005)
Journal of Vertebral Subluxation Research, July 5th, pp 1-6.
Objective: A pilot study to gather preliminary information regarding chiropractic care and possible links to immune status and improved aspects of health and quality of life.
Methods: The study followed 11 novice chiropractic subjects (7 males, 4 females) over a period of 9 months. Other than presenting with biomechanical complaints, the subjects represented a healthy population as determined by history, complete blood count, and immune status. Over a 9 months period, subjects received chiropractic adjustments when indicated. A self-reported quality of life questionnaire was completed by each subject following the initial visit (baseline), and at 3 and 9 months reassessment periods. At the same intervals, a complete blood count and an immune panel including absolute counts and percentages for CD3, CD4, CD8, CD20, CD56 and CD4/CD8 ratio were determined.
Results: Subjects demonstrated significant reductions in all chiropractic indicators at 3 months (p = 0.00) and 9 months (p = 0.00) compared to baseline. A positive change in Life Enjoyment occurred from 3 months to 9 months (p = 0.026), representing a large clinical effect (0.80). Significant negative correlations were also observed between motion palpation findings and CD56% and absolute CD56 count at baseline, suggesting a stress related link. Overall: The subjects appear to have maintained a healthy physiology. This conclusion is based on the complete blood count and immune profile throughout the duration of the study, as variations overall remained within reference values for healthy adults established by Auckland Hospital (New Zealand).
Conclusion: This pilot study has provided some preliminary information regarding chiropractic care and possible links to immune status and improved aspects of health and quality of life. Limited numbers of subjects, however, preclude definitive conclusions. Larger studies, including ill and healthy populations, to investigate the parameters presented herein and others such as killer cell activity will be necessary to test the conclusions presented.
Key words: Chiropractic, immune status, motion palpation.
Changes to autistic behavior following chiropractic care in a 30-month-old child
Fox, M. (2006)
J Clin Chiropractic Pediatrics, 7(1), 461-463.
Long term assessment of blood indices and immune panel profiling of subjects receiving chiropractic care: a pilot study
Boone, W. R., Oswald, P., Holt, K., Beck, R., Singh, K., & Ashton, A. (2006)
Journal of Vertebral Subluxation Research, June 7th, pp 1-11.
Objective: A pilot study to evaluate the approach of monitoring immune status as a feasible means of assessing physiological health in longitudinal studies that seek to ascertain changes in patient health status under chiropractic care.
Methods: The study presents findings profiling blood indices and the immune status of 11 novice chiropractic subjects (7 males, 4 females) at baseline, with re-assessments at 3 months and 9 months duration. The New Zealand group was compared to several other non-New Zealand healthy populations.
Results: Although significant changes occurred in blood indices and the immune profile in the present study group at 3 and 9 months re-assessments, the study values remained within the reference range for healthy adults. Significant positive correlations were seen for CD3% and CD8% at baseline and 3 months, suggesting a proportional increase or decrease over the range of values. It may be that the positive correlation is a reflection of the hosts’ resistance to viral infection and destruction of virus infected cells. Negative correlations were observed for CD56% and CD20% and CD56% and CD3% at 3 months and 9 months. CD 56% was also negatively correlated with CD8% and CD4% at different sampling periods. The inverse relationship among these lymphocyte subpopulations may reflect a natural balancing or redistribution of the overall lymphocyte subpopulation as individual cell types respond to a variety of immune challenges. The subjects in this pilot study sustained physiological health from the standpoint of maintaining a panel of blood indices and lymphocyte markers within normal reference ranges throughout the 9 months period. Further, the subjects’ blood indices and immune panels were comparable with population findings from other countries and ethnicities.
Conclusion: It is concluded that the approach of monitoring immune status is feasible as a means of assessing physiological health in longitudinal studies that seek to ascertain changes in patient health status.
Key words: Lymphocyte subpopulations, reference ranges, immune response, T lymphocytes, B lymphocytes, NK cells, CD4/CD8 ratio, chiropractic.
The Effect of Altered Peripheral Input on Sensorimotor Integration (Doctoral dissertation, Sport and Exercise Science)
Taylor, H. H. (2007)
The study of neural plasticity has expanded rapidly in the past decades, and has revealed the remarkable ability of the adult human central nervous system (CNS) to adapt to altered peripheral input from its ever-changing environment. However, this adaptive ability may not always represent a behavioral benefit for a given individual. Certain movement disorders may develop due to maladaptive changes in sensorimotor integration due to prolonged periods of repetitive movement. Joint dysfunction following injury may also lead to maladaptive central changes that cause ongoing pain and loss of function. This thesis has investigated the effects of altering peripheral input with two specific tasks (20 minutes of motor training and spinal manipulation) on sensorimotor integration.
Both single and dual peripheral nerve stimulation somatosensory evoked potential (SEP) techniques, as well as single and paired pulse transcranial magnetic stimulation (TMS) protocols were used to measure sensorimotor integration. The first studies demonstrated that motor training reduced the CNS’s ability to suppress dual input at the cortical level (increased N20-P27 and P22-N30 SEP ratios) and selectively altered short interval intracortical inhibition (SICI) and I-wave facilitation in both utilized and non-utilized muscles (increased SICI and reduced IwF in a non-utilized muscle, and the opposite effect in the trained muscle). The next set of experiments demonstrated selective changes in cortical processing in somatosensory and sensorimotor integration areas, and altered motor control of a thumb muscle following spinal manipulation (reduced N20 and N30 SEP peak amplitudes and a shortening of the TMS induced cortical silent period in the abductor pollicis brevis).
The final experiments demonstrated that cervical manipulation also altered cortical filtering of peripheral input utilizing the dual peripheral nerve stimulation SEP technique (decreased P22 – N30 SEP ratio). Furthermore, spinal manipulation prior to motor training altered the outcome of motor training alone (reduced P22-N30 SEP ratio post motor training as apposed to increased). These results suggest that the CNS at the cortical level had a greater ability to suppress the dual input following spinal manipulation and improves “sensory gating” following motor training when it is preceded with manipulation of dysfunctional cervical segments.
This thesis has significant implications for understanding the role of altered afferent input from joints and muscles on the ability to appropriately integrate somatosensory input.
Cervical spine manipulation alters sensorimotor integration: a somatosensory evoked potential study
Haavik-Taylor, H., & Murphy, B. (2007)
Clinical neurophysiology, 118(2), 391-402.
Objective: To study the immediate sensorimotor neurophysiological effects of cervical spine manipulation using somatosensory evoked potentials (SEPs).
Methods: Twelve subjects with a history of reoccurring neck stiffness and/or neck pain, but no acute symptoms at the time of the study were invited to participate in the study. An additional twelve subjects participated in a passive head movement control experiment. Spinal (N11, N13) brainstem (P14) and cortical (N20, N30) SEPs to median nerve stimulation were recorded before and for 30 min after a single session of cervical spine manipulation, or passive head movement.
Results: There was a significant decrease in the amplitude of parietal N20 and frontal N30 SEP components following the single session of cervical spine manipulation compared to pre-manipulation baseline values. These changes lasted on average 20 min following the manipulation intervention. No changes were observed in the passive head movement control condition.
Conclusions: Spinal manipulation of dysfunctional cervical joints can lead to transient cortical plastic changes, as demonstrated by attenuation of cortical somatosensory evoked responses.
Significance: This study suggests that cervical spine manipulation may alter cortical somatosensory processing and sensorimotor integration. These findings may help to elucidate the mechanisms responsible for the effective relief of pain and restoration of functional ability documented following spinal manipulation treatment.
Keywords: Cervical spine manipulation; Human; Somatosensory evoked potentials; Brain plasticity; Somatosensory system; Sensorimotor integration
Altered cortical integration of dual somatosensory input following the cessation of a 20 min period of repetitive muscle activity
Taylor, H. H., & Murphy, B. A. (2007)
Experimental brain research, 178(4), 488-498.
The adult human central nervous system (CNS) retains its ability to reorganize itself in response to altered afferent input. Intracortical inhibition is thought to play an important role in central motor reorganization. However, the mechanisms responsible for altered cortical sensory maps remain more elusive.
The aim of the current study was to investigate changes in the intrinsic inhibitory interactions within the somatosensory system subsequent to a period of repetitive contractions. To achieve this, the dual peripheral nerve stimulation somatosensory evoked potential (SEP) ratio technique was utilized in 14 subjects. SEPs were recorded following median and ulnar nerve stimulation at the wrist (1 ms square wave pulse, 2.47 Hz, 1 x motor threshold). SEP ratios were calculated for the N9, N11, N13, P14–18, N20–P25 and P22–N30 peak complexes from SEP amplitudes obtained from simultaneous median and ulnar (MU) stimulation divided by the arithmetic sum of SEPs obtained from individual stimulation of the median (M) and ulnar (U) nerves. There was a significant increase in the MU/M + U ratio for both cortical SEP components following the 20 min repetitive contraction task, i.e. the N20–P25 complex, and the P22–N30 SEP complex. These cortical ratio changes appear to be due to a reduced ability to suppress the dual input, as there was also a significant increase in the amplitude of the MU recordings for the same two cortical SEP peaks (N20–P25 and P22–N30) following the typing task. No changes were observed following a control intervention. The N20 (S1) changes may reflect the mechanism responsible for altering the boundaries of cortical sensory maps, changing the way the CNS perceives and processes information from adjacent body parts. The N30 changes may be related to the intracortical inhibitory changes shown previously with both single and paired pulse TMS. These findings may have implications for understanding the role of the cortex in the initiation of overuse injuries.
Transient modulation of intracortical inhibition following spinal manipulation
Haavik Taylor H, Murphy B. (2007)
Chiropractic Journal of Australia, Vol. 37, No. 3, Sep 2007: 106-116
Objective: To study the immediate sensorimotor neurophysiological effects of cervical spine manipulation using transcranial magnetic stimulation (TMS).
Design: Experimental design.
Setting: This study was carried out at the Human Neurophysiology Laboratory at the University of Auckland in Auckland, New Zealand.
Participants: Thirteen (13) subjects with a history of recurring neck stiffness and/or neck pain, but no acute symptoms at the time of the study were invited to participate in the study.
Intervention: Three (3) interventions were carried out in a randomised order: a control with no intervention, a passive head movement control condition, and a session of spinal manipulation of dysfunctional cervical joints.
Main Outcome Measures: Motor evoked potentials (MEP) and cortical silent periods (CSP) in the abductor pollicis brevis (APB) muscle of the dominant hand following transcranial magnetic stimulation (TMS) over the motor cortex.
Results: The major finding of this study was that the TMS-induced CSP measured in APB was significantly decreased for the first 20 minutes following spinal manipulation. No such changes were observed following either control condition, i.e. following no intervention or following passive head movement.
Conclusion: Spinal manipulation of dysfunctional cervical joints can lead to transient central neural plastic changes, as demonstrated by shortening of the TMS-induced CSP. This study suggests that cervical spine manipulation may alter sensorimotor integration. These findings may help to elucidate the mechanisms responsible for the effective relief of pain and restoration of functional ability documented following spinal manipulation treatment.