Background - Chiropractic & Osteopathy

Trigger points have been defined as discrete, hyperirritable foci usually located within a taut band of skeletal muscle [1]. The point is a well-circumscribed area in which pressure produces a characteristic referred pain, tenderness and autonomic phenomena [1]. Trigger points are considered an essential defining part of the myofascial pain syndrome, in which widespread or regional muscular pain is a cause of musculoskeletal dysfunction [2], as well as being associated with hyperalgesia, restriction of daily function or psychological disturbance [3]. Upon clinical presentation, trigger points are classified depending on certain characteristics. An active trigger point is defined as one with spontaneous pain, or pain in response to movement. It is tender on palpation, and may present with a referral pattern of pain, not at the site of the trigger point origin. A latent trigger point is a sensitive spot that causes pain or discomfort only in response to compression. Trigger points are reported to occur more frequently in cases of mechanical neck pain than in matched controls [4].

Patients may only become aware of pain when pressure is applied to a muscular point of restriction or weakness. The pathogenesis of trigger points is not clear, but it is believed they arise from more than one cause [5]. Fischer  has suggested that trigger points are due to the sensitisation of nerves and the tenderness results from the decrease in the pain pressure threshold. He further opines that the tissue damage associated with injury causes the release of inflammatory products that increase the sensitivity of the nerve to stimulation. These substances include bradykinins, 5-HT and prostaglandins, though a recent study found tender points in the trapezius muscle of patients with tension-type headache were not sites of ongoing inflammation [6]. Trigger points are also thought to arise from acute trauma or repetitive microtrauma, such as lack of exercise, poor nutrition, postural imbalances, vitamin deficiencies, sleep disturbances and joint problems [7].

One study suggests overloading of muscle fibres may lead to involuntary shortening, oxygen and vitamin deficiencies and increased metabolic demand on local tissues [8], and trigger points have been suggested as decreasing the extensibility and contractile efficiency of muscles, and possibly causing muscle fatigue [9]. This is yet to be confirmed by research. Trigger points have been shown to be active in fibromyalgia [10,11], as well as somatic tenderness secondary to visceral dysfunction [2], migraine and other forms of nonpathological headache [12], shoulder [13] neck [14] and back pain [15]. Specifically, Rosomoff and co-workers [15] demonstrated that  approximately 97% of persons with chronic intractable pain have trigger points, and of these, 45% have a non-dermatomal referred pain.

Furthermore, Rosomoff's team demonstrated that 100% of neck pain sufferers possessed the presence of trigger points and almost 53% of them had non-dermatomal referral [15]. However, it is worthy of note that no evidence describes the prevalence of trigger points of the neck and face in a normal population. Indirect evidence presented in the equine model suggests there to be significant differences between active trigger points and control points [16]. The diagnosis of a trigger point involves physical examination by an experienced therapist using a set of cardinal signs (Table 1) [1]. There have been many studies focused on the assessment of the reliability of detecting trigger points. Lew et al. [17] found that both inter and intra-rater reliability, using two highly trained examiners was poor, while Gerwin et al [18] found that extensive training of four clinicians together resulted in improved reliability for the identification of trigger points. Reeves et al. [19] demonstrated a moderate degree of intra and inter examiner reliability in determining the location of trigger points. In older studies values ranged from r = 0.68 to r = 0.86 [19].

In a study by Delaney and McKee [20], interclass correlation co-efficient (ICC) revealed inter-rater reliability to be high (values ranged from ICC = 0.82 to ICC = 0.92), and intra-rater reliabilities to be high (values ranged from ICC = 0.80 to ICC = 0.91) for the use of a pressure threshold meter in measuring trigger point sensitivity. In both clinical and experimental practice, a device such as the pressure algometer would be of great value for reliable quantification of trigger point sensitivities, once manually located. Fischer [5] demonstrated that the use of algometry in the detection of trigger points was a  reliable procedure. He assessed the pressure threshold of deep tenderness in soft tissues, before and after various forms of treatment such as physiotherapy and drug therapy. In addition, Reeves et al. [19] reviewed studies that demonstrated the reliability of the pressure algometer.

He found that an experimenter was able to reliably obtain similar measurements on two occasions, as well as produce similar scores to independent experimenters. He also noted that agreement was found between two experimenters when locating unmarked trigger points and measuring their sensitivity, but did stress the importance that experimenters were experienced and trained. In patients who present to manual therapists, the use of algometry can be used to reliably quantify the tenderness associated with a trigger point and can be used to diagnose their location as well as to qualify the degree of pressure sensitivity.

Trigger points are potential outcomes of dysfunction in a region, and conventional treatment is based around the release of this taut band of skeletal muscle. Manual therapy [21], chiropractic treatment [1,22], electric therapy [23], local anaesthetic [24] and active therapy [25] have all been claimed to provide relief of trigger point sensitivity. Injection therapies involved the use of local anaesthetic and saline, while it is postulated that massage and myofascial release aim to increase local circulation, improve mobility and relieve subcutaneous tightness. Furthermore, the presence of trigger points has been frequently associated with signs and symptoms in addition to pain [26], and these syndromes may be in found in disorders associated with chronic psychosocial factors [27].

Whilst it is likely the pathogenesis has at least a partly central mechanism, most approaches to the management of the trigger point phenomenon utilise only peripheral approaches to the points themselves. Therapy for trigger points requires an approach that enhances the central inhibition through pharmacological or behavioural techniques, and reduces the peripheral inputs to the maintenance of the reflexes by utilising physical therapies such as exercise [28], needling and digital pressure [29]. Offenbacher & Stucki [30] have also suggested that a combined approach to therapy would be warranted for patients exhibiting myofascial (as well as other) symptoms in conditions such as fibromyalgia. It was the specific aim of this research to investigate whether a new mind body technique called Neuro Emotional Technique (NET) could significantly relieve pain sensitivity of trigger points presenting in a cohort of neck pain sufferers.

This study investigated the effects of Neuro Emotional Technique (NET) on the sensitivity of trigger points presenting in regions of the neck including the suboccipital region, levator scapulae region, sternocleidomastoid insertion region and temporomandibular region, in a cohort of chronic neck pain sufferers. The results of the study could provide useful information or the treatment of cervical pain and related psychosocial problems.

Published by Peter Bablis Henry Pollard, Rod Bonello Macquarie University, Sydney, NSW, Australia

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