Heidi Haavik Taylor

Altered Sensorimotor Integration With Cervical Spine Manipulation

OBJECTIVE This study investigates changes in the intrinsic inhibitory and facilitatory interactions within the sensorimotor cortex subsequent to a single session of cervical spine manipulation using single- and paired-pulse transcranial magnetic stimulation protocols. METHOD Twelve subjects with a history of reoccurring neck pain participated in this study. Short interval intracortical inhibition, short interval intracortical facilitation (SICF), motor evoked potentials, and cortical silent periods (CSPs) were recorded from the abductor pollicis brevis and the extensor indices proprios muscles of the dominant limb after single- and paired-pulse transcranial magnetic stimulation of the contralateral motor cortex. The experimental measures were recorded before and after spinal manipulation of dysfunctional cervical joints, and on a different day after passive head movement. To assess spinal excitability, F wave persistence and amplitudes were recorded after median nerve stimulation at the wrist. RESULTS After cervical manipulations, there was an increase in SICF, a decrease in short interval intracortical inhibition, and a shortening of the CSP in abductor pollicis brevis. The opposite effect was observed in extensor indices proprios, with a decrease in SICF and a lengthening of the CSP. No motor evoked potentials or F wave response alterations were observed, and no changes were observed after the control condition. CONCLUSION Spinal manipulation of dysfunctional cervical joints may alter specific central corticomotor facilitatory and inhibitory neural processing and cortical motor control of 2 upper limb muscles in a muscle-specific manner. This suggests that spinal manipulation may alter sensorimotor integration. These findings may help elucidate mechanisms responsible for the effective relief of pain and restoration of functional ability documented after spinal manipulation.

THE EFFECTS OF SPINAL MANIPULATION ON CENTRAL INTEGRATION OF DUAL SOMATOSENSORY INPUT OBSERVED AFTER MOTOR TRAINING: A CROSSOVER STUDY

OBJECTIVE This study sought to investigate the influence of spinal dysfunction and spinal manipulation on the response of the central nervous system to a motor training task. METHODS The dual peripheral nerve stimulation somatosensory evoked potential (SEP) ratio technique was used in 11 subjects before and after a 20-minute typing task and again when the typing task was preceded with cervical spine manipulation. Somatosensory evoked potentials were recorded after median and ulnar nerve stimulation at the wrist (1 millisecond square wave pulse, 2.47 Hz, 1x motor threshold). The 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. RESULTS There was a significant increase in the MU/M+U ratio for both cortical (ie, N20-P25 and P22-N30) SEP components after the 20-minute repetitive contraction task. This did not occur when the motor training task was preceded with spinal manipulation. Instead, there was a significant decrease in the MU/M+U ratio for the cortical P22-N30 SEP component. The ratio changes appear to be due to changes in the ability to suppress the dual input as concurrent changes in the MU amplitudes were observed. DISCUSSION This study suggests that cervical spine manipulation not only alters cortical integration of dual somatosensory input but also alters the way the central nervous system responds to subsequent motor training tasks. CONCLUSION These findings may help to clarify the mechanisms responsible for the effective relief of pain and restoration of functional ability documented after spinal manipulation and the mechanism involved in the initiation of overuse injuries.

Altered Central Integration of Dual Somatosensory Input After Cervical Spine Manipulation

OBJECTIVE The aim of the current study was to investigate changes in the intrinsic inhibitory interactions within the somatosensory system subsequent to a session of spinal manipulation of dysfunctional cervical joints. METHOD Dual peripheral nerve stimulation somatosensory evoked potential (SEP) ratio technique was used in 13 subjects with a history of reoccurring neck stiffness and/or neck pain but no acute symptoms at the time of the study. Somatosensory evoked potentials were recorded after median and ulnar nerve stimulation at the wrist (1 millisecond square wave pulse, 2.47 Hz, 1 x motor threshold). The 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. RESULTS There was a significant decrease in the MU/M + U ratio for the cortical P22-N30 SEP component after chiropractic manipulation of the cervical spine. The P22-N30 cortical ratio change appears to be due to an increased ability to suppress the dual input as there was also a significant decrease in the amplitude of the MU recordings for the same cortical SEP peak (P22-N30) after the manipulations. No changes were observed after a control intervention. CONCLUSION This study suggests that cervical spine manipulation may alter cortical integration of dual somatosensory input. These findings may help to elucidate the mechanisms responsible for the effective relief of pain and restoration of functional ability documented after spinal manipulation treatment.

The Cervical Flexion-Relaxation Ratio: Reproducibility and Comparison Between Chronic Neck Pain Patients and Controls

Study Design. Reliability study. Objective. To determine the reproducibility of the cervical flexion-relaxation ratio (FRR) measured 4 weeks apart in a group of chronic neck pain patients and healthy control group and to compare the FRR between the 2 groups. Summary of Background Data. The cervical FRR measures the ability of the neck extensor muscles to relax during forward flexion, similar to the lumbar FRR. Its reliability and ability to discriminate neck pain patients from controls has not been investigated. Methods. Fourteen participants with chronic neck pain and a control group of 14 individuals with no neck pain were recruited via advertisement and word of mouth. The cervical FRR was determined at baseline and 4 weeks later using standardized electromyographic data collection and analysis procedures. Results. The mean FRR value for the combined left and right side data for the neck pain groups was 1.93 ± 0.8, and 1.73 ± 0.61 at 4-week follow-up. The intraclass correlation coefficient (ICC) was 0.83 (95% CI = 0.67–0.92). Three participants in the control group developed neck pain in the 4 weeks and their data were not included in the reliability calculation. For the control group, the combined (left and right side) mean FRR value was 4.09 ± 1.58 at baseline and 4.27 ± 1.71 on retest 4 weeks later. The ICC (intraclass r) was 0.89 (95% confidence interval = 0.76–0.95). The overall ICC for the combined groups was 0.92 (95% confidence interval = 0.86–0.95). An independent 2 group t test revealed a significant difference in the baseline FRR data between the control group and the neck pain group (P < 0.001). Conclusion. The cervical extensor muscles exhibit a consistent flexion-relaxation phenomenon in healthy control subjects and the measurement is highly reproducible when measured 4 weeks apart in both controls and chronic neck pain patients. The FRR in neck pain patients is significantly higher than in control subjects suggesting that this measure may be a useful marker of altered neuromuscular function.

The Effect of Spinal Manipulation on the Efficacy of a Rehabilitation Protocol for Patients With Chronic Neck Pain: A Pilot Study

OBJECTIVE This pilot study sought to (1) determine whether a 4-week period of chiropractic care improved the ability of chronic neck pain patients to respond to an 8-week period of exercise rehabilitation and (2) determine effect sizes to use in sample size calculations for future studies. METHODS Twenty male and female participants (age, 43 +/- 12 years; body mass index, 27 +/- 4.5 [mean +/- SD]) with chronic nonspecific neck pain were randomized into either a chiropractic care combined with exercise or an exercise only group. Group 1 received 4 weeks of chiropractic care, and group 2 waited 4 weeks before both groups participated in an 8-week exercise intervention. The following outcome measures were assessed in week 1 (baseline), week 4, and at week 12: Neck Disability Index (NDI); Visual Analogue Scale (VAS), both now and worst; neck flexion-relaxation response; and feed-forward activation (FFA) times. A repeated-measures analysis of variance was used to evaluate the changes in the NDI and VAS over time. Effect sizes were calculated for changes in neuromuscular parameters. RESULTS There were significant decreases in the NDI score (P < .001) and VAS in (P < .005) in both groups with no significant differences between the groups. Effect sizes (ESs) were as follows: NDI (.293); VAS now (.175); VAS worst (.392); flexion-relaxation (.636); FFA times: sternocleidomastoid (.1321), anterior scalene (.195). This lead to sample size estimates as follows: flexion-relaxation response, 64 subjects per group; NDI, 145 subjects per group; VAS, 166 subjects per group. CONCLUSIONS Chiropractic care combined with exercise and exercise alone are both effective at reducing functional disability and pain in chronic nonspecific neck pain patients. Future studies will need at least 64 subjects per group to determine if there are differences between the groups and if these differences are attributable to changes in neuromuscular measures.

Interexaminer reliability of a leg length analysis procedure among novice and experienced practitioners.

OBJECTIVE The purpose of this study was to evaluate the interexaminer reliability of a leg length analysis protocol between an experienced chiropractor and an inexperienced chiropractic student who has undergone an intensive training program. METHODS Fifty participants, aged from 18 to 55 years, were recruited from the New Zealand College of Chiropractic teaching clinic. An experienced chiropractor and a final-year chiropractic student were the examiners. Participants were examined for leg length inequality in the prone straight leg and flexed knee positions by each of the examiners. The examiners were asked to record which leg appeared shorter in each position. Examiners were blinded to each others findings. kappa statistics and percent agreement between examiners were used to assess interexaminer reliability. RESULTS kappa analysis revealed substantial interexaminer reliability in both leg positions and also substantial agreement when straight and flexed knee results were combined for each participant. kappa scores ranged from 0.61, with 72% agreement, for the combined positions to 0.70, with 87% agreement, for the extended knee position. All of the kappa statistics analyzed surpassed the minimal acceptable standard of 0.40 for a reliability trial such as this. CONCLUSION This study revealed good interexaminer reliability of all aspects of the leg length analysis protocol used in this study.