Local Twitch Response Research Articles

Interexaminer reliability of the palpation of trigger points in the trunk and lower limb muscles

Hsieh C-YJ, Hong C-Z, Adams AH, Platt KJ, Danielson CD, Hoehler FK, Tobis JS. Interexaminer reliability of the palpation of trigger points in the trunk and lower limb muscles. Arch Phys Med Rehabil 2000;81:258-64. Objectives: To determine the interexaminer reliability of palpation of three characteristics of trigger points (taut band, local twitch response, and referred pain) in patients with subacute low back pain, to determine whether training in palpation would improve reliability, and whether there was a difference between the physiatric and chiropractic physicians. Design: Reliability study. Setting: Whittier Health Campus, Los Angeles College of Chiropractic. Participants: Twenty-six nonsymptomatic individuals and 26 individuals with subacute low back pain. Intervention: Twenty muscles per individual were first palpated by an expert and then randomly by four physician examiners. Main Outcome Measures: Palpation findings. Results: Kappa scores for palpation of taut bands, local twitch responses, and referred pain were.215,.123, and.342, respectively, between the expert and the trained examiners, and.050,.118, and.326, respectively, between the expert and the untrained examiners. Kappa scores for agreement for palpation of taut bands, twitch responses, and referred pain were.108, −.001, and.435, respectively, among the nonexpert, trained examiners, and −.019,.022, and.320, respectively, among the nonexpert, untrained examiners. Conclusions: Among nonexpert physicians, physiatric or chiropractic, trigger point palpation is not reliable for detecting taut band and local twitch response, and only marginally reliable for referred pain after training. © 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Current Research on Myofascial Trigger Points–Pathophysiological Studies

SUMMARYObjectives: To summarize recent studies on myofascial trigger point [MTrP] to further clarify the mechanism of MTrP.Methods: To review recent clinical and basic science studies related to the pathophysiology of MTrPs.Results: There are multiple loci in an MTrP region. A clinical MTrP characteristically exhibits a sensory component [sensitive locus] and a motor component [active locus]. A sensitive locus is the site from which spot tenderness, referred pain [ReP], and local twitch response [LTR] can be elicited by mechanical stimulation. Sensitive loci [probably sensitized nociceptors] can be widely distributed in the whole muscle, but are concentrated in the endplate zone. An active locus is the site from which spontaneous electrical activity [SEA] can be recorded. Active loci are dysfunctional endplates, since SEA is essentially the same as electrical activity recorded from an abnormal endplate as reported by neurophysiologists. An MTrP is always found in a taut band which is histologically relate...

Myofascial trigger points in intercostal muscles secondary to herpes zoster infection of the intercostal nerve

Chronic pain in the chest wall is a major complication after herpes zoster infection of intercostal nerves. It is usually difficult to control pain of such origin. Two cases are reported of postherpetic neuralgia after herpes zoster infection involving the intercostal nerves. Both patients had shooting, burning, aching, and localized pain in the muscle supplied by the involved intercostal nerves 1 to 3 months after onset. Compression palpation of a tender spot in one of these muscles induced a referred pain that followed the corresponding interspace, usually in the distal anterior direction. Local twitch responses could be elicited during injection of 0.5% or 1% lidocaine into one of these tender spots; the pain in the interspace was consistently eliminated immediately after injection. One patient had complete pain relief after three series of injections. The effect of pain relief for the other patient lasted for 1 to 2 weeks after the initial injection and lasted progressively longer (up to 2 months) after repeated injections. It appears that many of the tender spots formed in intercostal muscles after herpes zoster are myofascial trigger points that respond to injection with referred pain, local twitch responses, and immediate pain relief.

Myofacial trigger point

Myofascial trigger points are one of the most common causes of acute and chronic musculoskeletal pain. Contrary to popular belief, myofascial trigger points can be primary, and not just secondary due to other non-muscular pathology. The main criteria, for which the interrater reliability has been established, include the presence of a taut band, a local twitch response, an exquisite tender point within the taut band, and typical referred pain patterns. During the past few years, the actual existence and high prevalence of myofascial trigger points are supported by worldwide research findings. The “energy crisis theory” describes the peripheral pathophysiologic events of myofascial trigger points. In most cases myofascial trigger points can be treated successfully both in acute and chronic pain syndromes. Several treatment options are available including manual therapy, injections, dry needling, and electrotherapeutic modalities. In some cases neuroplastic changes in the spinal dorsal horn and sympathetic-afferent coupling play a role in the development of chronic pain syndromes and complicate the treatment.

Referred pain elicited by palpation and by needling of myofascial trigger points: A comparison

Objective: To investigate the occurrence of referred pain (REP) elicited by palpation (Pal-ReP) or by needle injection (Inj-ReP) of myofascial trigger point (MTrP), and to assess the correlated factors, including the pain intensity of an active MTrP and the occurrence of local twitch response (LTR). Design: Correlational study. Patients: Ninety-five patients who were treated with MTrP injections. Intervention: MTrP injections. Main Outcome Measure: Pain intensity of MTrP and occurrence of Pal-ReP, Inj-ReP, and LTR. Results: Both Pal-ReP and Inj-ReP were elicited in 53.9% of MTrPs. Inj-ReP, but not Pal-ReP, was elicited in 33.7% of MTrPs. Both Pal-ReP and Inj-ReP were unobtainable in 12.3% of MTrPs. The occurrence of ReP was significantly correlated to the pain intensity of active MTrP and the occurrence of LTR. Conclusion: ReP could be elicited more frequently by needling than by palpation. The frequency of occurrence in ReP mainly depends on pain intensity of an active MTrP.

Identifying and Treating Myofascial Pain Syndrome

Though common, myofascial Pain syndrome can be difficult to recognize and distinguish from underlying entities. It is often confused with fibromyalgia. Diagnosis hinges on the identification of painful muscle trigger points that, when palpated, create local twitch responses and refer pain in predictable patterns. With appropriate treatment, such as stretch and spray, trigger point injections, or massage therapy, prognosis is good. Perpetuating factors, such as poor posture or workplace ergonomics, also need to be addressed.

Interrater reliability in myofascial trigger point examination

The myofascial trigger point (MTrP) is the hallmark physical finding of the myofascial pain syndrome (MPS). The MTrP itself is characterized by distinctive physical features that include a tender point in a taut band of muscle, a local twitch response (LTR) to mechanical stimulation, a pain referral pattern characteristic of trigger points of specific areas in each muscle, and the reproduction of the patient's usual pain. No prior study has demonstrated that these physical features are reproducible among different examiners, thereby establishing the reliability of the physical examination in the diagnosis of the MPS. This paper reports an initial attempt to establish the interrater reliability of the trigger point examination that failed, and a second study by the same examiners that included a training period and that successfully established interrater reliability in the diagnosis of the MTrP. The study also showed that the interrater reliability of different features varies, the LTR being the most difficult, and that the interrater reliability of the identification of MTrP features among different muscles also varies.

The Localized Twitch Responses in Responsive Taut Bands of Rabbit Skeletal Muscle Fibers Are Related to the Reflexes at Spinal Cord Level

Objective: This study investigated spinal cord mediation of rabbit localized twitch responses [R-LTRs] by transection of the spinal cord and later of the peripheral nerve. Rabbit localized twitch response [R-LTR] is a brisk contraction of a group of rabbit skeletal muscle fibers which is most responsive to mechanical stimulation of the pressure-sensitive site, the trigger spot [TrS]. An R-LTR is analogous to a local twitch response of a human taut band, and a TrS is analogous to a human myofascial trigger point [TrP]. Methods: The electromyographic [EMG] activity of R-LTRs was recorded for the biceps femoris muscle of 5 rabbits [ages: 2-3 months]. Each animal was anesthetized in a way that preserved most peripheral reflexes. R-LTRs were elicited by mechanical-tap stimuli [delivered by a solenoid-driven blunt metal probe] to the TrS. The percentage of occurence of R-LTRs and the changes in maximal amplitude and duration of EMG activity of R-LTRs [before the spinal cord transection at T4, T5, or T6, and the...

Comparison of Local Twitch Responses Elicited by Palpitation and Needling of Myofascial Trigger Points

Objectives: To compare local twitch responses [LTRs] that are produced by manual snapping palpation to those produced by needle penetration of myofascial trigger points [TrPs]. Methods: One hundred and five LTRs were recorded electromyographically from 13 TrPs in 13 muscles and 9 subjects. Sixty-four LTRs were elicited by snapping palpation and forty-one by subsequently inserting a monopolar electromyographic [EMG] probe needle repeatedly into the same TrP region. The electrical activity of an LTR was recorded from a response EMG needle inserted 4 cm from the TrP in the same palpable taut band and with snapping palpation also from a surface electrode overlying the response needle electrode. Results: The EMG characteristics of the LTRs elicited by needle insertion and those elicited by snapping palpation were not significantly different in the mean number of discharges per LTR, mean duration, or discharge density. Conclusions: At the level of detail examined in this study, no indication of a difference was...

Persistence of local twitch response with loss of conduction to and from the spinal cord

A local twitch response (LTR) is a brisk contraction of a taut band of skeletal muscle fibers elicited by snapping palpation of a trigger point (TrP) in that band. The LTR is a clinically valuable objective sign that confirms the presence of a myofascial TrP. A translent burst of electromyographic (EMG) activity can be recorded from taut band fibers when an LTR is elicited by snapping palpation of TrP. A previous study of the human extensor digitorum muscle during ischemia suggested that both central and local pathways can be involved in the propagation of LTRs. In this study, EMG activity of LTRs in the third finger extensor muscle were recorded bilaterally in a patient with a unilateral brachial plexus lesion. This patient had complete loss of nerve conduction involving the posterior cord of the right brachial plexus as confirmed by EMG and nerve conduction studies and by neurological examination at 6 months after injury. EMG activity (measured as discharge duration and maximal amplitude) on the paralyzed side was significantly reduced (p < 0.01) as compared with the unaffected side, but had not disappeared. Three more studies were done at 7, 8, and 17 months after injury when the motor and sensory functions were recovered progressively. The EMG activity of LTRs recovered on the paralyzed side in parallel with the motor and sensory recovery. These findings indicate that the transmission of LTR depends mainly on the central nervous system with a possible minor degree of local transmission.

Considerations and Recommendations Regarding Myofascial Trigger Point Injection

Objectives: The purpose of this article is to review the previously published data on myofascial trigger point injection and to present a proposed technique of myofascial trigger point [TrP] injection modified from tha described by Drs. Travell and Simons. Findings: Trigger point injection is an effective and valuable procedure to inactivate an active TrP, and subsequently relieve the pain and tightness of the muscle involved in myofascial pain syndrome. It is essential to elicit a local twitch response [LTR] during TrP injection to obtain the best results of immediate relief of pain. LTR is a brisk twitching of the muscle fibers of the taut band during mechanical stimulation [including needling] on the most sensitive site, the TrP region. Sometimes, other remote TrPs can also be inactivated if the "key TrP" is appropriately selected for injection based on skillfull clinical judgement. The trigger point injections are indicated for quick relief of acute, subacute, or chronic myofascial pain, for substitution of narcotic medicine, for restoration of functional impairment due to myofascial trigger points, or for supplementary therapy of chronic myofascial pain to facilitate its recovery. It is generally recommended to use 0.5% of procaine or lidocaine at a dose of 0.5-1.0 cc per TrP region for TrP injection. The proposed technique of TrP injection includes identification of the taut band containing the active TrP, skin preparation with sterile technique, rapid needle insertion into the multiple sites of a TrP region, injection of local anesthetic only if LTR is elicited, hemostatis, stretching and spray, and appropriate post-injection cares including cold or hot pack application, therapeutic exercise, therapeutic massage, and home program. The frequency and total number of injections should be determined based on clinical judgement. Some complications, such as muscle fiber damage, excessive bleeding, infection, syncope, or internal organ injury, may occur, but are usually preventable with careful and skillful injection technique. Conclusions: A technique of trigger point injection is proposed. Other than the traditional injection method, local twitch responses should be elicited as many times as possible during injection. The insertion of the needle should be quick to minimize muscle fiber damage. This technique is usually very effective to obtain immediate and complete pain relief.

Symptomatology and clinical pathophysiology of myofascial pain

Myofascial pain syndromes, fibromyalgia, and articular dysfunctions may all be contributing to our patients' ubiquitous musculoskeletal pain problems that generally are poorly understood and poorly managed. Thepectoralis minor myofascial pain syndrome, for example, results from trigger points (TrPs) activated by stress overload of the muscle. Symptoms of pain referred to the shoulder and ulnar aspect of the arm and forearm, and of pain on reaching around and behind the body, are characteristic. Findings include restricted stretch range of motion and some weakness of the muscle, taut bands of muscle fibers, and focal trigger point tenderness of each taut band on palpation. Snapping palpation at the TrP elicits a local twitch response (LTR). The increased muscle tension of a pectoralis minor syndrome commonly entraps the lower trunk of the brachial plexus, producing symptoms of a cervical radiculopathy.

Fibrositis/fibromyalgia: A form of myofascial trigger points?

The diagnostic criteria for fibrositis and primary fibromyalgia are similar to those for myofascial pain syndromes due to trigger points. Tender points in muscles are likely to be myofascial trigger points; nonmuscular tender points clearly are not myofascial trigger points, but may be areas of tenderness referred from such trigger points. Myofascial trigger points refer pain to a distance and restrict range of motion of the muscle. They are associated with a palpable taut band that exhibits a local twitch response of the muscle, and they are responsive to treatment. Persistence of myofascial trigger points is due to perpetuating factors that can usually be corrected. Although their number is unknown, it is likely that some patients who are diagnosed as having fibrositis/fibromyalgia have multiple myofascial trigger points aggravated by a powerful perpetuating factor and also have a systemic disease process independent of the myofascial trigger points. Since myofascial pain syndromes are treatable, these patients would benefit greatly by identification and relief of the myofascial component of their pain.

Electromyographic changes associated with the local twitch response in myofascial pain syndrome

Electromyographic changes associated with the local twitch response in myofascial pain syndrome

Myofascial origins of low back pain. 1. Principles of diagnosis and treatment.

Myofascial trigger points (TPs) are frequently overlooked sources of acute and chronic low back pain. An active myofascial TP is suspected by its focal tenderness to palpation and by restricted stretch range of motion. The restricted lengthening of the muscle is due to the tense band of muscle fibers in which the TP is located. The presence of a TP is confirmed by a local twitch response and by reproduction of its known pattern of referred pain, which matches the distribution of the patient's pain. Only an active TP causes a clinical pain complaint; a latent TP does not. The pain can be relieved by the stretch-and-spray procedure, ischemic compression, or precise injection of the TP with procaine solution. Relief is usually long lasting only if mechanical and systemic perpetuating factors are corrected.

Local twitch response evoked by palpation and needle penetration of a trigger point in human muscle

Rehabilitation Medicine Service, VA Medical Center, Long Beach, CA 90822, and Department of PM & R, University of California, IrvineU.S.A