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Disinhibition in the gamma motoneuron circuitry: a neglected mechanism for understanding myofascial pain syndromes?

Dysregulation in the gamma motoneuron circuitry is proposed as one mechanism to explain the development of trigger point activity in myofascial pain syndrome. Dysregulation in this context is defined operationally as significantly (and functionally) different levels of electrical activity detected in the same muscle on the left and right sides of the body that is persistently present with movement of that muscle. Neurophysiological concepts as they pertain to muscles and motor control principles are reviewed. Research is integrated that ties together material from diverse fields of psychology and medicine. Dysregulation in the gamma motoneuron circuitry may lead to disinhibition of muscle that causes it to remain hyperactive after contraction, generate excessive electrical activity during movement, and/or inappropriately coactivate with other muscles during movement. Any or all of these phenomena may occur with dysregulation. Such dysregulation may be corrected by learning. Immediate clinical implications are discussed, including the addition of specifically targeted neuromuscular retraining procedures via surface electromyography, as well as some conceptual and research issues that require further clarification.

Facial Muscles↗

Masticatory performance in patients with anterior disk displacement without reduction in comparison with symptom-free volunteers.

Masticatory function can be impaired by craniomandibular disorders. The aim of this study was to assess masticatory performance in patients with an anterior disc displacement (ADD) without reduction. In the experiments, 29 patients and 33 age- and gender-matched volunteers chewed artificial test food for 60 chewing strokes. The collected remains of the test food were filtered, dried, fractionated by a sieving procedure, and weighed. The particle size distribution was then described using a cumulative distribution function. Patients and controls were clinically examined, and patients were asked to complete a pain questionnaire. Comparison with controls, patients showed significantly reduced masticatory performance. Patients that had had a disorder longer than 3 yr tended to display less reduction of their masticatory performance. Neither the treatment methods used, nor restriction of daily life activities or pain intensity were significantly correlated with masticatory performance. Jaw mobility was significantly reduced in patients. More than half of the patients and none of the controls had joint noises and trigger points in the masticatory muscles. Pain was present, in particular, during chewing and maximal opening of the mouth. It was concluded that patients with ADD without reduction have a significantly reduced masticatory performance.

Activities of Daily Living↗

Intermittent androgen suppression for prostate cancer: rationale and clinical experience.

Research on hormonal treatments of prostate cancer over the past 20 y have focused on maximizing androgen ablation through combination therapy. Maximal androgen ablation increases treatment-related side-effects and expense and fails to prolong time to androgen-independent (AI) progression. The rationale behind intermittent androgen suppression (IAS) is based on: (1) observations that androgen ablation is palliative, not curative in most patients where quality of life must be considered; (2) assumption that immediate androgen ablation is superior to delayed therapy in improving survival of patients with prostate cancer; and (3) the hypothesis that if tumor cells which survive androgen withdrawal are forced into a normal pathway of differentiation by androgen replacement, then apoptotic potential might be restored and progression to androgen independence may be delayed. Observations from animal model studies suggest that progression to androgen-independence involves adaptive responses to androgen deprivation which are, in turn, modulated by intermittent androgen replacement. Supported by these animal model observations, several centers have now tested the feasibility of IAS therapy in non-randomized groups of patients with prostate cancer using serum PSA as trigger points. Experimental and clinical data suggest that prostate cancer is amenable to control by IAS. IAS may offer clinicians an opportunity to improve quality of life in patients with prostate cancer by balancing the benefits of immediate androgen ablation (delayed progression and prolonged survival) while reducing treatment-related side effects and expense. Whether time to progression and survival is affected in a beneficial or adverse way is being studied in randomized, prospective protocols. The purpose of this article is to review the rationale behind IAS, compare observations from published series, and discuss potential indications and treatment strategies using IAS.

Journal Article↗

Asymmetry in jaw-jerk reflex latency in craniomandibular dysfunction patients with unilateral masseter pain.

The purpose of the present study was to elucidate the effects of unilateral masseter muscle pain on the jaw-jerk reflex. The latency and peak-to-peak amplitude of bilateral electromyographic activity recorded at the masseter muscles during the jaw-jerk reflex were measured in 18 patients with craniomandibular dysfunction (CMD) with strictly unilateral masseter pain or tenderness and 10 control subjects using a computerized recording and analysis system. The reflex was elicited, at the mandibular rest position, by tapping the centre of the chin downwards with a reflex hammer incorporating a microswitch that triggered the sweep of the recording apparatus upon contact with the chin. In the CMD group, the jaw-jerk latency on the affected side (6.89 +/- 0.98 ms) was significantly shorter (P < 0.01) than that on the unaffected side (7.59 +/- 0.92 ms). In the control group, there was no difference between the jaw-jerk latencies on the right (7.06 +/- 0.64 ms) and the left (7.08 + 0.65 ms) sides. The range of side asymmetry for jaw-jerk latencies in the CMD group was greater than that in the control group. In six patients, the latency difference exceeded 1 ms. The asymmetry of latency of the jaw-jerk reflex was thought to be due to facilitation on the side with masseter pain or tenderness. This facilitation on the ipsilateral side might be produced by enhanced gamma drive induced by sustained nociceptive stimulation. Such effects may be related with clinically derived concepts regarding such muscle dysfunction as myospastic activity or trigger points.

Adolescent↗

Cutaneous sensory stimulation leading to facial flushing and release of calcitonin gene-related peptide.

A patient is described with a 17-year history of intractable left-sided facial pain. The pain occurred daily in 5 sec spasms to a maximum of one every 2-3 min and was restricted to the left upper face. It was associated with rhinorrhoea on the left and often with ipsilateral facial flushing. Conventional therapy, including carbamazepine, baclofen and three posterior fossa explorations, had not provided lasting relief. Local facial stimulation by tapping a painful trigger point led to both pain and flushing of the face ipsilaterally. During this flushing, blood was collected and assayed using sensitive radioimmunoassays for several neuropeptides (neuropeptide Y, substance P, vasoactive intestinal polypeptide and calcitonin gene-related peptide). A marked (119%) increase in calcitonin gene-related peptide was noted in the external jugular vein blood ipsilaterally during the flushing with no change in the other peptides measured. To quantitate the effect of calcitonin gene-related peptide on human extracranial vessels, standard pharmacological procedures were used to examine the potency of the peptide as a vasodilator of human facial artery. The IC50 of calcitonin gene-related peptide for the prostaglandin F2 alpha-precontracted human facial artery was 10(-9) mol/l. The relevance of these observations to the clinical problem of migraine is considered.

Calcitonin Gene-Related Peptide↗

Occipital neuralgia treated by intradural dorsal nerve root sectioning.

The term occipital neuralgia was first used in 1821 to describe a characteristic pain in the region innervated by the greater occipital nerve. Since that time numerous authors have failed to reach a consensus concerning the presentation, cause, and treatment of this entity. Review of these previous works reveals that the term occipital neuralgia encompasses a collection of signs and symptoms which develop secondary to a variety of different disease processes. We have treated nine patients suffering from severe occipital pain with associated C2 hypesthesia, unilateral retro-orbital pain, and occipital or C2 tubercle trigger points by intradurally sectioning the C1-C4 dorsal rootlets (C4 if shoulder pain existed). All patients had been treated previously with various modalities without success. This paper discusses the results obtained in these patients.

Female↗

The 'dry-needle technique': intramuscular stimulation in tension-type headache.

The 'dry-needle technique', an intramuscular stimulation technique carried out by using a fine solid, 1-inch long, 30-gauge needle, was investigated in the treatment of tension-type headache (TTH) in a randomized, placebo-controlled trial. Fifteen patients with TTH received intramuscular needle insertions into six designated trigger points, while 15 controls received subcutaneous insertions. Headache indices, muscle tenderness and neck ROMs were evaluated before and after treatment. Mean headache indices improved significantly after treatment, both in the treatment group and in the placebo group, but the difference between the two groups was insignificant. In the treatment group the tenderness score and the neck ROM limitation score were significantly improved after treatment, while there was no significant improvement in the placebo group. We conclude that more and larger controlled, comparative trials are needed to show whether the dry-needle technique is an effective non-pharmacological alternative for the treatment of TTH.

Acupuncture Therapy↗

Treatment of fibromyalgia with antidepressants: a meta-analysis.

BACKGROUND: Fibromyalgia is a common, poorly understood musculoskeletal pain syndrome with limited therapeutic options. OBJECTIVE: To systematically review the efficacy of antidepressants in the treatment of fibromyalgia and examine whether this effect was independent of depression. DESIGN: Meta-analysis of English-language, randomized, placebo-controlled trials. Studies were obtained from searching MEDLINE, EMBASE, and PSYCLIT (1966-1999), the Cochrane Library, unpublished literature, and bibliographies. We performed independent duplicate review of each study for both inclusion and data extraction. MAIN RESULTS: Sixteen randomized, placebo-controlled trials were identified, of which 13 were appropriate for data extraction. There were 3 classes of antidepressants evaluated: tricyclics (9 trials), selective serotonin reuptake inhibitors (3 trials), and S-adenosylmethionine (2 trials). Overall, the quality of the studies was good (mean score 5.6, scale 0-8). The odds ratio for improvement with therapy was 4.2 (95% confidence interval [95% CI], 2.6 to 6.8). The pooled risk difference for these studies was 0.25 (95% CI, 0.16 to 0.34), which calculates to 4 (95% CI, 2.9 to 6.3) individuals needing treatment for 1 patient to experience symptom improvement. When the effect on individual symptoms was combined, antidepressants improved sleep, fatigue, pain, and well-being, but not trigger points. In the 5 studies where there was adequate assessment for an effect independent of depression, only 1 study found a correlation between symptom improvement and depression scores. Outcomes were not affected by class of agent or quality score using meta-regression. CONCLUSION: Antidepressants are efficacious in treating many of the symptoms of fibromyalgia. Patients were more than 4 times as likely to report overall improvement, and reported moderate reductions in individual symptoms, particularly pain. Whether this effect is independent of depression needs further study.

Adult↗

Treatment of chronic cervical-associated headache with botulinum toxin A: a pilot study.

OBJECTIVE: To see whether therapy with botulinum toxin A may prove to be an effective treatment for headache of musculoskeletal origin. BACKGROUND: Headache is a common finding associated with neck injury. Cervicogenic headache, which is believed to be attributable to injury of the ligaments, muscles, or joints of the cervical spine, is centered in the occipital region with pain referred to the frontotemporal region. Botulinum toxin A produces prolonged muscle relaxation, which is dose dependent and can be easily targeted to affected muscles. METHODS: This randomized, double-blind, placebo-controlled study compares outcome measures in 26 patients suffering from chronic headache subsequent to a cervical whiplash injury. One half of the patients received botulinum toxin A, 100 units, diluted in 1 mL of saline, while the other half received just saline (1 mL). Five cervical trigger points received 0.2 mL each of injectant via a 30-gauge needle. Outcome measures included subjective head pain based on visual analog scales, as well as range of neck motion. Follow-up assessments were carried out at 2 and 4 weeks after treatment. RESULTS: Fourteen subjects who received botulinum toxin A and 12 who received saline completed the study. At both 2 and 4 weeks post injection, the treatment group showed a significant improvement in pain and range of motion from preinjection levels (P<.01). The placebo group demonstrated no statistically significant changes at any posttreatment time.

Adult↗

Regional head and face pain relief following lower cervical intramuscular anesthetic injection.

BACKGROUND: Although cervical trigger point intramuscular injections are commonly used to relieve localized neck pain, regional head pain relief from lower cervical paravertebral injections has not been reported previously. PURPOSE: To evaluate the safety and efficacy of such injections in a selected group of patients with intractable head or face pain. METHODS: In a series of patients with chronic head or face pain, local anesthetic was injected into the lower cervical spine paravertebral musculature approximately 1 to 2 inches lateral to the seventh cervical spinous process. RESULTS: In addition to producing rapid relief of palpable scalp or facial tenderness (mechanical hyperalgesia and allodynia pain), this lower cervical intramuscular injection technique alleviated associated symptoms of nausea, photophobia, and phonophobia in patients with migrainous headache. CONCLUSION: Our results suggest that lower cervical intramuscular anesthetic injection may be an effective treatment for head or face pain.

Adult↗

Technical aspects of radiofrequency.

Radiofrequency (RF) is an alternating electric field with an oscillating frequency of 500,000 Hz. If the resulting current flows through a percutaneously introduced electrode, heat will be produced around the electrode because the body tissue acts as a resistor. RF can, therefore, be used to ablate nervous tissue in the treatment of chronic pain. This method has gained acceptance for percutaneous cordotomy and for the treatment of trigeminal neuralgia. For spinal pain, the method had little success initially, but since the introduction of small diameter instrumentation, the results have markedly improved. he mechanism of action of RF has not been challenged until recently even though there was awareness that some observations were not consistent with the heat concept. The formation of heat is not the only occurrence during RF treatment, however. The tissue surrounding the electrode is also exposed to the RF electric field. This exposure has a biological effect as has been demonstrated both in cells in a cell culture and in the exposure to RF of dorsal root ganglia, resulting in transsynaptal induction of early gene expression in the dorsal horn. The mode of action of RF is, therefore, uncertain at the moment. The method of pulsed RF is based on the concept that the production of heat has been a by-product of RF treatment and that the clinical effect is due to exposure to the electric field. In pulsed RF, the generator output is interrupted to allow for the elimination of heat in the silent period. The early results have been encouraging, but the results of controlled, prospective studies are not yet available. Since there are now 2 almost diametrically opposed views on the mode of action of RF, it is difficult to give recommendations for treatment. The decision is easy for indications for which heat RF has traditionally been contraindicated such as the treatment of peripheral nerves and trigger points. When the application of heat carries a potential risk, for instance if the dorsal root ganglion is the target structure, the use of pulsed RF is also recommended. As for the medial branch the situation is controversial. Since there are controlled studies available showing the effect of heat lesions, it is recommended that the technique should not be changed until further studies have been completed. Finally, the equipment for RF treatment is described and safety issues are discussed.

Journal Article↗

Interventions in chronic pain management. 2. New frontiers: invasive nonsurgical interventions.

UNLABELLED: Invasive nonsurgical techniques have a central role in the management of patients suffering from acute and chronic pain. This article surveys common percutaneous pain procedures: trigger point injections, intra-articular injections, spinal injections, nerve blocks, radiofrequency lesioning (thermocoagulation and pulsed-mode), epidural adhesiolysis and decompressive neuroplasty, neural mapping, intradiskal and intra-annular procedures, neuromodulation, continuous intrathecal analgesia, and deep brain stimulation. Physiatrists must understand the guiding principles behind these procedures before practicing interventional pain management. OVERALL ARTICLE OBJECTIVE: To review invasive, nonsurgical pain management procedures.

Adjuvants, Immunologic↗

Superior cluneal nerve entrapment.

BACKGROUND AND OBJECTIVES: Pain due to superior cluneal nerve entrapment is an infrequent cause of unilateral low back pain. Here we present a case of acute unilateral low back pain treated by superior cluneal nerve (SCN) block. CASE REPORT: A 55-year-old woman presented to the outpatient clinic suffering from unilateral low back pain localized to right iliac crest and radiating to the right buttock. Her history was taken, physical examination was performed, and a thorough radiologic evaluation was performed to minimize radiculopathy and facet syndromes as causative. After transient pain relief with a diagnostic trigger point injection, entrapment of SCN was diagnosed and therapeutic nerve block with local anesthetic and steroid combination was performed. CONCLUSION: SCN is prone to entrapment where it passes through the fascia near the posterior iliac crest. Unilateral low back pain and deep tenderness radiating to the ipsilateral buttock are the clinical findings accompanying SCN entrapment. The case presented emphasizes the relief of possible SCN after limiting other etiologic causes of low back pain.

Female↗

Pain on intramuscular injection of bupivacaine, ropivacaine, with and without dexamethasone.

BACKGROUND AND OBJECTIVES: We wished to determine which long-acting local anesthetic would produce the least pain on injection for treatment of myofascial pain disorders. We compared the pain on intramuscular injection of bupivacaine, ropivacaine, bupivacaine with dexamethasone, ropivacaine with dexamethasone, and needle placement alone. METHODS: Thirty volunteers received 5 injections each: (1) needle only, (2) bupivacaine 0.5%, (3) ropivacaine 0.5%, (4) bupivacaine 0.5% with dexamethasone 0.13 mg/mL, and (5) ropivacaine 0.5% with dexamethasone 0.13 mg/mL. The injections were made in the volunteers' upper trapezius muscles; there was a 15-minute interval between injections. The sequence of injections was randomized by Latin square design. The intensity of pain was rated on a 0 to 10 cm visual analogue scale (VAS) score. Neither the investigator nor the volunteer was aware of the nature of the injectate. The pH of the injected solutions was checked to determine if differences in the intensity of pain on injection were due to differences in the pH of the solutions. RESULTS: The VAS pain scores were 3.1 +/- 2.4 for needle only, 4.4 +/- 2.8 for bupivacaine, 2.5 +/- 2.0 for ropivacaine, 4.7 +/- 2.7 for bupivacaine/dexamethasone, and 3.7 +/- 2.2 for ropivacaine/dexamethasone. The pain on injection of ropivacaine was significantly less than the pain on injection of bupivacaine or bupivacaine/dexamethasone. The pH values of the solutions were as follows: (1) bupivacaine, 5.50; (2) ropivacaine, 5.57; (3) bupivacaine/dexamethasone, 6.64; and (4) ropivacaine/dexamethasone, 6.60. CONCLUSIONS: The pain on intramuscular injection of bupivacaine is significantly more intense than with ropivacaine. The difference in the intensity of the pain on injection between bupivacaine and ropivacaine does not appear to be related to differences in pH. The results of our study have implications on the choice of the local anesthetic used in trigger point injections.

Adult↗

Radiofrequency sacroiliac joint denervation for sacroiliac syndrome.

BACKGROUND AND OBJECTIVES: Radiofrequency (RF) denervation of the sacroiliac (SI) joint has been advocated for the treatment of sacroiliac syndrome, yet no clinical studies or case series support its use. METHODS: We report the results of a consecutive series of 50 SI joint RF denervations performed in 33 patients with sacroiliac syndrome. All patients underwent diagnostic SI joint injections with local anesthetic before denervation. Changes in visual analog pain scores (VAS), pain diagrams, physical examination (palpation tenderness over the joint, myofascial trigger points overlying the joint, SI joint pain provocation tests, and range of motion of the lumbar spine), and opioid use were assessed pre- and postdenervation. RESULTS: The criteria for successful RF denervation were at least a 50% decrease in VAS for a period of at least 6 months; 36.4% of patients (12 of 33) met these criteria. Failure of denervation correlated with the presence of disability determination and pain on lateral flexion to the affected side. The average duration of pain relief was 12.0 +/- 1.2 months in responders versus 0.9 +/- 0.2 months in nonresponders (P < or = 0.0001). A positive response was associated with an atraumatic inciting event. Successful denervation was associated with a change in the pain diagram and a reduction in the pattern of referred pain, a normalization of SI joint pain provocation tests, and a reduction in the use of opioids. CONCLUSIONS: This study suggests that RF denervation of the SI joint can significantly reduce pain in selected patients with sacroiliac syndrome for a protracted time period. Moreover, certain abnormal physical findings (i.e., SI joint pain provocation tests) revert to normal for the duration of the analgesia.

Adult↗

Possibilities and limitations of automated platelet counting procedures in the thrombocytopenic range.

The clinical decision to proceed with prophylactic platelet transfusions is widely based on trigger points for platelet counts being equal to 20, 10, or even 5 x 10(9)/L. But an increasing number of publications show evidence that the conventional automated platelet counting methods are unable to provide consistently accurate results in this lower thrombocytopenic range. These measurement errors are mainly associated with the most commonly used impedance principle; optical methods seem to be more precise. The problems of counting imprecision in the low thrombocytopenic range can be avoided with direct or indirect immunological counting methods using monoclonal antibodies or by time-consuming manual procedures. But how should new counting procedures be evaluated? Which method should be used as the "gold standard" for platelet counting? A way out of this apparent dilemma is the application of a statistical procedure as proposed by Gautschi et al. This mathematical model allows a reference method independent evaluation of new methods by calculation of the limits of detection (LD) and limits of quantification (LQ) based on the imprecision profile of the investigated method. Using this evaluation procedure, it can be shown that immunological automated counting methods can provide reliable, sufficient, and prompt platelet counts, especially in the thrombocytopenic range.

Antibodies, Monoclonal↗

[Botulinum toxin in tension-type headache].

Botulinum toxin has meanwhile been approved for a number of indications. It is also gaining acceptance in other indications with a major focus on pain. The most common type of headache is tension-type headache (TTH) the pathogenesis of which has not yet been unfolded. As it looks there are vascular, myofascial and supraspinal factors intertwined. It is felt that headache is triggered by myofascial stimuli. The application of botulinum toxin is an intelligent alternative since the favorable effect of pharmacologic and other therapies is limited. Application of BTX should be considered when the pericranial muscles are involved. One of the effects produced lies in the reduction of muscular stress, muscular ischemia and muscle tone. We still don't know whether additional mechanisms such as retrograde uptake and direct antiinflammatory potential are involved. Current data permit the conclusion that headaches are decreased in their frequency and distinctiveness. Significant untoward effects are not to be expected. Neither the ideal dose nor the optimum selection of injection sites have been established as yet, an individual injection scheme is apparently most promising. Injection of the trigger points seems to make sense.

Botulinum Toxins↗

[The piriformis syndrome].

A rare mentioned and therefore and often overlooked cause of low back pain with sciatica. The piriformis muscle arises from the anterior surface of the sacrum and inserts on the superior border of the greater trochanter. Functionally, the piriformis muscle is an external rotator and abductor of the thigh. Muscle spasm or on inflammatory process set into motion by the spasm cause an epineurial irritation of the sciatic nerve. The symptoms present almost identically to lumbar disk syndrome, except for the consistent absence of true neurologic findings. Diagnosis is accomplished by rectal palpation of myofascial trigger points within the piriformis muscle, also pain and weakness on resistant abduction-external rotation of the thigh. The essential therapy is the injection of local anesthetic and a small dose of corticoid into the precise focal point of hyperirritability deep in the belly of the muscle. Recurrences are uncommon.

Diagnosis, Differential↗