Chiropractic Works


To study the immediate sensorimotor neurophysiological effects of cervical spine manipulation using somatosensory evoked potentials (SEP’s).




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 brainstem and cortical SEP’s to median nerve stimulation were recorded before and for thirty minutes after a single session of cervical spine manipulation, or passive head movement.




There was a significant decrease in the amplitude of parietal and frontal SEP components following the single session of cervical spine manipulation compared to pre-manipulation baseline values.

These changes lasted on average twenty minutes following the manipulation intervention.

No changes were observed in the passive head movement control condition.




Spinal manipulation of dysfunctional cervical joints can lead to transient cortical plastic changes, as demonstrated by attenuation of cortical somatosensory evoked responses.




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.


Key Points from Dan Murphy

1. Spinal manipulation is a commonly used conservative treatment for neck, back, and pelvic pain.

2. The effectiveness of spinal manipulation in the treatment of acute and chronic low back and neck pain has been well established by outcome-based research.

3. Spinal dysfunction will alter afferent input to the central nervous system.

4. Altered afferent input to the central nervous system leads to plastic changes in the central nervous system. (Very Important)

5. Neural plastic changes take place both following increased and decreased afferent input. (Extremely Important)

6. Both painful and painless joint dysfunction will inhibit surrounding muscles.

7. Joint dysfunction causes afferent driven increases in neural excitability (facilitation) to muscles that can persist even after the initiating afferent abnormality is corrected. (This suggests that a muscle afferent problem can persist even after the joint component of the subluxation is corrected. The chronic component of the subluxation may be plastic changes that cause long-term alteration of muscle afferentation.) This article clearly supports that the joint component, the muscle component, and the neurological component of the subluxation complex are influenced by traditional joint-cavitation spinal adjusting.

8. The altered neural processing that occurs as a consequence of joint dysfunction provides a rationale for the effects of spinal manipulation on neural processing that have been described in the literature. (Very Important)

9. Spinal dysfunction alters the balance of afferent input to the central nervous system and this altered afferent input may lead to maladaptive neural plastic changes in the central nervous system, and spinal manipulation can effect this. (Very Important)

10.The clinical evidence for joint dysfunction that requires manipulation includes:

A. Tenderness on joint palpation,

B. Restricted intersegmental range of motion,

C. Palpable asymmetry of intervertebral muscle

D. Abnormal or blocked joint play and end-feel,

E. Sensorimotor changes in the upper extremity.

[I recall in the teachings of Richard Stonebrink, DC, in the orthopedic diplomate program twenty-five years ago, the importance of always documenting (in our daily records) the evidence that the patient had a manipulatable spinal lesion (subluxation). His evidence was identical to these. Dr. Stonebrink would stress that such documentation would always make the case unique to chiropractic and consequently make the chiropractor the only expert in the case.]

11.The most reliable spinal-dysfunction-indicators are tenderness with palpation of the dysfunctional joint, and alterations of segmental range of motion.

12.High velocity, low amplitude thrust spinal manipulation with the head held in lateral flexion, with slight rotation and slight extension is a standard manipulative technique used by manipulative physicians, physiotherapists and chiropractors.

13.High velocity manipulation alters reflex EMG activity and alters afferent input to the central nervous system. (Important)

14.High-velocity manipulation causes significant cortical SEP amplitude attenuation in at least the frontal and parietal cortexes.

15.Passive head movements do not cause changes in cortical firing.

16.A single session of spinal manipulation of dysfunctional joints resulted in attenuated cortical (parietal and frontal) evoked responses. These changes most likely reflect central changes. (Very Important)

17.The cortical function of different individuals responded differently to spinal adjusting. [This indicates that variables other than the adjustment, itself, can influence the cortical responses in a given individual]

18.The significantly decreased somatosensory cortical SEP occurred in all post-manipulation measurements, indicating enhanced active inhibition because the cervical manipulations could have altered the afferent information originating from the cervical spine (from joints, muscles, etc.).

19.The passive head movement SEP experiment demonstrated that no significant changes occurred following a simple movement of the subject’s head. Our results are, therefore, not simply due to altered input form vestibular, muscle or cutaneous afferents as a result of the chiropractors touch or due to the actual movement of the subject’s head. This, thus, suggests that the results in this study are specific to the delivery of the high-velocity, low-amplitude thrust to dysfunctional joints. [Extremely Important]

20.Displacement of vertebrae is signaled to the central nervous system by afferent nerves arising from deep intervertebral muscles, and this is improved with adjusting the adjacent dysfunctional joint.

21.Joint dysfunction leads to bombardment of the central nervous system with Ia afferent signaling from surrounding intervertebral muscles. Spinal manipulation reduces excessive afferent signals from adjacent intervertebral muscles, which improves altered afferent input to the central nervous system. This changes the way the central nervous system responds to any subsequent input.

22.Episodes of acute pain following injury induce plastic changes in the sensorimotor system, prolonging the episode of pain and playing a roll in establishing chronic neck pain conditions. (Very Important) The reduced cortical SEP amplitudes observed in this study following spinal manipulation may reflect a normalization of such injury/pain-induced central plastic changes, which may reflect one mechanism for the improvement of functional ability reported following spinal manipulation. (Extremely Important)

23.Spinal manipulation of dysfunctional joints may modify transmission of neuronal circuitries, not only at a spinal level, but at a cortical level, and possibly also deeper brain structures such as the basal ganglia. (Very Important)

24.Cervical spine manipulation alters cortical [brain] somatosensory processing and sensorimotor integration.

25.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.


Comment by Dan Murphy

One of the central themes of the neurology diplomate program taught by Ted Carrick, DC, is that chiropractic spinal adjusting influences the cortical brain, creating plastic changes. This article very much supports that perspective.


Dr. Dan Murphy graduated magna cum laude from Western States Chiropractic College in 1978. He received Diplomat status in Chiropractic Orthopedics in 1986. Since 1982, Dr. Murphy has served part-time as undergraduate faculty at Life Chiropractic College West, currently teaching classes to seniors in the management of spinal disorders. He has taught more than 2000 postgraduate continuing education seminars. Dr. Murphy is a contributing author to both editions of the book Motor Vehicle Collision Injuries and to the book Pediatric Chiropractic.


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