Luciana Uemoto1,2), Marco Antonio C. Garcia3), Cresus Vinicius D. Gouvêa4),
Oswaldo V. Vilella4), and Thays A. Alfaya4)
The aim of this study was to evaluate different approaches to deactivating myofascial
trigger points (MTPs). Twenty-one women with bilateral MTPs in the masseter muscle were randomly divided into three groups: laser therapy, needle treatment and control. Treatment effectiveness was evaluated after four sessions with intervals ranging between 48 and 72 h. Quantitative and qualitative methods were used to measure pain perception/sensation. The Wilcoxon test based on results expressed on a visual analog scale (VAS) demonstrated a significant (P < 0.05) decrease in pain only in the laser and needle treatments groups, although a significant increase in the pressure pain threshold was evident only for needling with anesthetic injection (P = 0.0469), and laser therapy at a dose of 4 J/cm² (P = 0.0156). Based on these results, it was concluded that four sessions of needling with 2% lidocaine injection with intervals between 48 and 72 h without a vasoconstrictor, or laser therapy at a dose of 4 J/cm², are effective for deactivation of MTPs.
Myofascial pain syndrome (MPS) is one of the most frequent causes of pain involving the orofacial region, i.e., the head and neck (1). A key feature of this syndrome is the presence of myofascial trigger points (MTPs) in the affected muscles. When these points are active,
patients often complain of pain distant from the site, e.g., in the head, ear, mandible, temporomandibular joint, teeth, eyes and cervical spine. This feature prompts patients to consult a wide range of health professionals, including otorhinolaryngologists, ophthalmologists and neurologists. Several tests are usually performed, but no abnormality is usually detected. The signs and symptoms of this syndrome have not been clarified. However, certain diagnostic criteria have been reported, such as a palpable and hypersensitive taut muscle band – if the muscle is accessible – acknowledgement of pain by the patient when pressure is applied to the active MTP, and soreness when the affected muscle is stretched (2-7). Therefore, diagnosis is purely clinical, based on a detailed history and thorough physical examination performed by muscle palpation and observation of motor function (4). MTPs can be classified as active (single) or latent (multiple), depending on their clinical features. As previously stressed, there is local sensitivity in the taut muscle bands and pain at a distance, which causes the patient to respond by twitching, flinching, or showing facial expressions of discomfort during palpation (2,4,6).
Moreover, any pain or tenderness is generally located ipsilateral to the detected MTPs. The latent MTPs are generally multiple and do not cause referred pain, but cause result in muscle shortening or weakness (4,6). No consensus has yet been reached regarding the
etiology of MPS. Direct or indirect factors may be associated. The former consist of direct injury to the muscle (macrotrauma) or repeated microtrauma caused by parafunctional (2,3) and improper postural habits, or recreational or occupational activities that produce repetitive stress in a specific muscle or group of muscles (2). Indirect factors cause muscle weakness, predisposing the muscle to the development of trigger points. Contributing factors include nutritional deficiencies, structural disharmonies, such as occlusal disorder, physical inactivity, sleep disorders and joint problems (2-4) as well as any continuous source of deep pain and emotional distress (4,8,9).
Given its multifactorial etiology, no standard treatment protocol for MPS is currently available. Instead, several treatment alternatives have been suggested. The main objective has been to restore the normal length, position and full range of motion of the muscle(s), including the identification and removal of perpetuating factors, in addition to MTP deactivation (4,5). Suggested treatments for deactivation of MTPs include ultrasound (6), application of pressure or massage (6), transcutaneous electrical nerve stimulation (TENS) (6,10), ethyl chloride spray and stretch techniques (6), acupuncture (6), dry needling, (4,6,11), or needling with injection of certain agents, (6) and low-level laser therapy (1,2,6,12-14).