Bialoskyet al (2008) proposes a model of neurophysiological mechanisms in an attempt to explain the impact of Manipulation Therapy (MT) on pain experience in individuals. Within this model, a ‘spinal cord mediated’ mechanism is considered. This theory is supported by citation of a paper by Maliszaet al(2003) who demonstrated (using MRI) decreased activation of the dorsal horn of the spinal cord following MT (knee mobilisations) in rats injected with noxious stimulus into the hind paw and ankle followed by the application of soft touch to the area, compared with no MT applied.
Similarly, Wright et al (1994) hypothesized a hypoalgesic effect of Manipulation Therapy through the impact on activation of descending pain inhibitory system (DPIS). In further explanation, as there is an ascending pathway to the brain that initiates the conscious realization of pain, there is also a descending pathway which modulates pain sensation (DPIS). It is hypothesized that the effect of MT involves interruption or reduction of nociceptive stimuli somewhere along this path between input and processing. Increased activity at the dorsal horn has been highlighted as the main cause of dysfunction in sympathetically maintained pain.
An activity of the sympathetic nervous system has been shown to be inextricably related to the perception of pain and to the alleviation of pain (Lovick, 1995). Reported effects of manipulation on pain are hugely variable. This may reflect the variable state of the sympathetic nervous system at the time of treatment affecting the response.
Although not ‘novel’, the impact of MT on the cervical spine on Lateral Epicondylopathy (LE) is not yet widely acknowledged by clinicians. This was an area I researched last year when we were directed to filter referrals for all patient with LE into the Hand therapy service as a wait list management strategy, to be managed by the Occupational Therapy trained hand therapists, who were unable to assess or treat the cervical spine (or shoulder). When I researched any relationship between the cervical spine and LE, I was very surprised to find the common link was Manipulation Therapy in almost every journal article located.
Gunn and Milbrandt (1976) first investigated the relationship between the cervical spine and LE in patients resistant to ‘usual conservative measures’. Treatment involved mobilization and traction which was found to bring relief from pain but also a sympathoexcitatory response. Over time the effect of MT at the cervical spine on LE has been extensively investigated. A number of papers have further investigated this sympathoexcitatory response. Vincenzinoet al (1994) investigated the effect of 2 spinal MT techniques on skin conduction and temperature in distal C6 dermatome in asymptomatic subjects, demonstrating MT at the cervical spine led to an immediate sympathoexcitatory effect.
Vicenzinoet al (1998) investigated this proposed model in which manipulative therapy produces a treatment specific initial hypoalgesic and sympathoexcitatory effect by activating a DPIS. This was a randomized, double-blinded, placebo-controlled, repeated-measures study utilizing 7 outcome measures reflecting the pain and sympathetic changes. They found that MT produced a treatment-specific initial hypoalgesic and sympathoexcitatory effect beyond that of placebo or control. This hypoalgesic effect has been further supported by Fernandez-de-laspenaset al (2007).
Most recently Fernandez-Carneroet al (2011) compared immediate effects of cervical Vs thoracic Manipulation Therapy on PPT and PFGS, finding an immediate short-term increase in hypoalgesic effect in patients with LE. The author concludes that ‘despite the clinical effectiveness of cervical manipulation in this condition, the possible neurophysiologic mechanisms of action remain elucidated’.
Once the mechanism of effect of MT is established it will open doors for many novels uses. If it does indeed have an impact on the sympathetic nervous system then utilizing MT in patients with disorders involving the sympathetic nervous system such as diabetic neuropathy may be viable. Most relevant to myself as a musculoskeletal physiotherapist, if MT does interrupt the DPIS, there may be scope to utilize spinal MT in any peripheral musculoskeletal pathology where the pain is a significant issue.
Fernandez-De-Las-Penas C, Perez-De-Heredia M, Brea-Rivero M, Miangolarra-Page JC.The immediate effect on pressure pain threshold following a single cervical spine manipulation in healthy subjects. J Orthop Sports PhysTher 2007; 37(6):325-329
Fernandez-Carnero J, Cleland JA, La ToucheArbizu R. Examination of a motor and hypoalgesic effects of cervical Vs thoracic spine manipulation in patients with lateral epicondylalgia: a clinical trial. J Manipulative PhysiolTher 2011; 34: 432-440
Gunn C C, Milbrandt W E. Tennis elbow, and the cervical spine. Can Med Assoc J 1976; 8 (13): 803-809
Lovick TA. Interactions between descending pathways from the dorsal and ventrolateral periaqueductal gray matter in the rat. In: Depaulis A, Bandler R, eds. The midbrain periaqueductal gray matter. New York: Plenum Press; 1991. P.101-20. (cited by Vincenzino B, Collins D, Benson H, Wright A.An investigation of the relationship between manipulative therapy-induced hypoalgesia and sympathoexcitation. J Manipulative PhysiolTher 1998; 21(7): 448-453)
Malisza KI, Stroman PW, Turner A, Gregorash I, Foniok T, Wright A. Functional MRI of the rat lumbar spinal cord involving painful stimulation and the effect of peripheral joint mobilization. J MagnReson Imaging. 18: 152-159
Vincenzino B, Collins D, Wright T. Sudomotor changes induced by neural mobilization techniques in asymptomatic subjects. J Man ManipTher 1994; 2 (2): 66-74
Vincenzino B, Collins D, Benson H, Wright A. An investigation of the relationship between manipulative therapy-induced hypoalgesia and sympathoexcitation. J Manipulative PhysiolTher 1998; 21(7): 448-453
Wright A, Thurnwald P, O’Callaghan J, Smith J, Vincenzino B. Hyperalgesia in tennis elbow patients. J Musculoskelet Pain 1994; 2 (4): 83-97