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Increase in Cortical Drive Following Spinal Manipulation


Chiropractic care is commonly thought to have a beneficial effect on the functioning of the human body by affecting the nervous system. Evidence indicates that chiropractic adjustments result in plastic changes in sensorimotor integration within the central nervous system in human participants, particularly within the prefrontal cortex. Adjustments appear to alter the net excitability of the low-threshold motor units, increase cortical drive, and prevent fatigue (see this blog).  This same group of researchers have more recently found an increase cortical drive to upper and lower extremity muscles following manipulation as measured by motor evoked potential. The researchers suggested the effects were due to descending cortical drive and could not be explained by changes at the level of the spinal cord (although they can’t rule that out completely).  Two experiments were conducted.  In experiment one, transcranial magnetic stimulation input–output (TMS I/O) curves for an upper limb muscle (abductor pollicus brevis; APB) were recorded, along with F waves prior to and after either spinal manipulation or a control intervention for the same subjects on two different days. During these two separate days, lower limb TMS I/O curves and movement related cortical potentials (MRCPs) were recorded from tibialis anterior muscle (TA) before and after spinal manipulation. Spinal manipulation resulted in a 54.5% ± 93.1% increase in maximum motor evoked potential (MEPmax) for APB and a 44.6% ± 69.6% increase in MEPmax for TA. 
They conclude that “Spinal manipulation may therefore be indicated for the patients who have lost tonus of their muscle and or are recovering from muscle degrading dysfunctions such as stroke or orthopaedic operations. These results may also be of interest to sports performers. We suggest these findings should be followed up in the relevant populations.”

Reference: Haavik H, Niazi IK, Jochumsen M, Sherwin D, Flavel S, Türker KS. Impact of Spinal Manipulation on Cortical Drive to Upper and Lower Limb Muscles. Brain Sci. 2016 Dec 23;7(1).

 

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Spinal Manipulation Alters Somatosensory Processing in the Prefrontal Cortex

adobestock_49611047Over the last decade, research has demonstrated that spinal manipulation can change various aspects of nervous system function, including muscle reflexes, cognitive processing, reaction time, and the speed at which the brain processes information. One research group from New Zealand (Haavik et al) has hypothesized that the articular dysfunction part of the chiropractic clinical construct, the vertebral subluxation, results in altered afferent input to the central nervous system (CNS) that modifies the way in which the CNS processes and integrates all subsequent sensory input. This processing (i.e., sensorimotor integration) is a central nervous system (CNS) function that appears most vulnerable to altered inputs.

Investigators utilizing techniques such as transcranial magnetic stimulation and somatosensory evoked electroencephalographic (EEG) potentials have suggested that neuroplastic changes occur in the brain (e.g. primary sensory cortex, primary motor cortex, prefrontal cortex, basal ganglia, and cerebellum).  Inducing and recording somatosensory evoked potentials (SEPs) is emerging in scientific literature relating to spinal manipulation (SM). There is evidence to support that SEPs are able to elucidate differences in cortical activity associated with SM. Studies with only a few recording EEG electrodes allow investigation of evoked potential amplitudes and latencies and have shown changes in the N30 somatosensory evoked potential (SEP) amplitudes following spinal manipulation.  The N30 response from the frontal lobe peak reflects sensory integration.

With recent advances in the spatial resolution of EEG, it is becoming possible to better anatomically localize the signal.  With this study, the authors aimed to utilize brain electrical source analysis to explore which brain sources are responsible for changes in N30 amplitude following a single session of spinal manipulation.

Nineteen young (average age 26 years) subclinical pain volunteers were included in the study. Subclinical pain (SCP) refers to recurrent spinal ache, pain, or stiffness for which the subject had not sought treatment. Subjects were excluded if they had: no evidence of spinal dysfunction, they were in current pain, they had sought previous treatment for their spinal issues, or they had contraindications to receiving spinal manipulation. The EEG signals were recorded with the Neuroscan System from 62 scalp electrodes using the extended 10-20 system montage. Supine subjects received electrical stimulations applied to the median nerve at the right wrist to evoke SEPs. Two trials of 1000 pulses were given in each session: one trial before treatment (control or chiropractic) and one trial after the treatment.

The entire spine and both sacroiliac joints were assessed for segmental dysfunction and adjusted where they were deemed necessary by an experienced chiropractor. Assessment for dysfunction included tenderness to palpation of the relevant joints, restricted intersegmental range of motion, asymmetric muscle tension, and any abnormal or blocked joint play and end-feel of the joints. The control (sham) involved one of the investigators (not a chiropractor) simulating a chiropractic treatment session. This included passive and active movements of the subject’s head, spine, and body, similar to what was done by the chiropractor who provided the actual chiropractic treatment.

Results:

  • SEPs were successfully recorded in all subjects
  • the majority of subjects were able to correctly guess which intervention group they were in (SM or sham)
  • there was a significant post-intervention difference between the two groups – specifically the N30 amplitude was reduced in the spinal manipulation group following the treatment, while it remained stable in the control group
  • source localization indicated that the prefrontal cortex tended to have the highest strength during the time interval between 20 and 60 ms
  • source strength analysis revealed that chiropractic treatment reduced the strength of the prefrontal source, while all the other strengths remained stable

Key Points:

  • Results from this study confirmed that spinal manipulation of dysfunctional spinal segments reduces the N30 SEP peak amplitude and demonstrated that this change is taking place in the prefrontal cortex
  • This suggests that, at least in part, the mechanisms by which spinal manipulation improves performance are due to a change in function at the prefrontal cortex
  • It is possible that the mechanisms behind pain relief following spinal manipulation in low level pain patients are due to improved sensorimotor integration and appropriate motor control, as this is the key function of the prefrontal cortex

Source: Lelic D, Niazi IK, Holt K, Jochumsen M, Dremstrup K, Yielder P, Murphy B, Drewes AM, Haavik H. Manipulation of Dysfunctional Spinal Joints Affects Sensorimotor Integration in the Prefrontal Cortex: A Brain Source Localization Study. Neural Plast. 2016;2016:3704964.

 

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Brain Activity Following Chiropractic Manipulation

35856944_sResearch on chiropractic spinal manipulation (CSM) has been conducted extensively worldwide, and its efficacy on musculoskeletal symptoms has been well documented.  Previous studies have documented potential relationships between spinal dysfunction and the autonomic nervous system and that chiropractic treatment affects the autonomic nervous system. The authors of this study hypothesized that CSM might induce metabolic changes in brain regions associated with autonomic nervous system functions as assessed with positron emission tomography (PET).  Positron emission tomography is a nuclear medicine imaging technique that allows quantification of cellular and molecular processes in humans such as cerebral glucose metabolism which is thought to reflect regional neuronal activities.

Participants were men between the ages of 20-40 who had neck pain and shoulder stiffness.

A crossover study design was used such that subjects served as their own controls to compare their resting brain activity to their brain activity following chiropractic manipulation.  Half of the participants completed the control condition first while the other half completed the chiropractic condition first.  The participants came back sometime between 1 and 6 weeks later to complete their remainder condition.  Chiropractic consisted of a single Activator Methods assessment and treatment session by a chiropractor lasting 20 minutes.  The control condition consisted of 20 minutes of rest.  Immediately after each condition, 18F-labeled fluorodeoxyglucose (FDG) was injected.  FDG is an excellent imaging marker of brain metabolism (glucose consumption).  PET scanning followed administration of FDG.

Additional outcome measures included pain (VAS), Stress Response Scale (SRS-18) and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30), trapezius muscle tone, and salivary amylase.

Results of the PET image analysis showed statistically significant changes in regional cerebral metabolism between rest and treatment conditions.  With chiropractic treatment, increased glucose metabolism was observed in the inferior prefrontal cortex, anterior cingulate cortex,  middle temporal gyrus; decreased glucose metabolism was observed in the cerebellar vermis and visual association cortex.  Reduced metabolism in the cerebellar vermis may be related to reductions is pain, mental stress, muscle tone and sympathetic tone.  Activation of the anterior cingulated cortex and inferior prefrontal cortex may arise from sympathetic relaxation.

The mean SRS-18 and EORTC QLQ-C30 scores were significantly lower in the treatment condition indicating improved stress response and improved quality of life. Mean VAS pain score comparison was significantly improved with treatment.  Additionally, measurement of trapezius muscle tone and salivary amylase showed significant reduction with chiropractic suggesting improved sympathetic relaxation.

 

Reference: Tashiro M, Ogura T, Masud M, Watanuki S, Shibuya K, Yamaguchi K, Itoh M, Fukuda H, Yanai K. Cerebral metabolic changes in men after chiropractic spinal manipulation for neck pain. Altern Ther Health Med. 2011 Nov-Dec;17(6):12-7.

 

 

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Dr. Heidi Haavik

006- Brain Adjustments with Dr. Heidi Haavik

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Learn what happens in your brain when a chiropractor adjusts your spine.  Dr Heidi Haavik is a chiropractor and a neurophysiologist who has worked in the area of human neurophysiology for over 15 years. Heidi has a PhD in human neurophysiology from the University of Auckland. Her work has been instrumental in building the base of scientific evidence demonstrating the efficacy of chiropractic care in improving people’s health and wellbeing. As a researcher, she has investigated the effects of chiropractic adjustments of dysfunctional spinal segments (vertebral subluxations) on somatosensory processing, sensorimotor integration and motor cortical output.

Dr Haavik is the Director of Research at the New Zealand College of Chiropractic where she has established the Centre for Chiropractic Research. Dr Haavik is also an Adjunct Professor at the University of Ontario, Institute of Technology in Oshawa, Canada and is a member of the World Federation of Chiropractic’s Research Council. Dr Haavik has received numerous research awards and has published a number of papers in chiropractic and neurophysiology journals. She has presented her work to both chiropractic and neuroscience communities around Australasia, North America and Europe. She is on the Editorial Board of the Journal of Manipulative and Physiological Therapeutics and Journal of Chiropractic Education. She was named Chiropractor of the year in 2007 by both the New Zealand Chiropractic Association and the New Zealand College of Chiropractic Alumni Association.  She is also the author of a textbook – The Reality Check which describes in easy to understand language what happens in the brain when a chiropractor adjusts dysfunctional segments in your spine.

Read about Dr Haavik at her website, and get her book and posters at heidihaavik.com.  Subscribe to Dr Haavik’s research service at haavikresearch.com to get great evidence-informed marketing material for chiropractic practices including among other things, videos for your website that explain how chiropractic works.  Interested in donating toward her research efforts?  Contact her at haavikresearch.com.

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Dr. Haavik and Dr. Smith at the Ohio State Chiropractic Association Convention, 2015

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Dr. Haavik’s book: The Reality Check