Trigger Points and Myofascial Pain Syndrome

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Myofascial pain syndrome (MPS) describes a variety of conditions characterized by sensory, motor, and autonomic symptoms caused by myofascial trigger points.

Definition:

Myofascial pain syndrome (MPS) describes a variety of conditions characterized by sensory, motor, and autonomic symptoms caused by myofascial trigger points. According to Travell & Simons’ “Myofascial Pain and Dysfunction”, myofascial trigger point (TrP) is a hyper-irritable focus within a taut band of skeletal muscle, located in the muscular tissue and /or its associated fascia. The spot is painful on compression, and can evoke characteristic referred pain and autonomic phenomena.

Pathophysiology:

There are numbers of theories trying to explain the formation of TrPs. Among those, Travell’s initial trauma theory stated that a taut band in a muscle was necessary as a precursor to TrP development. Taut bands are common in asymptomatic people and once they are present, they are at risk of TrP development. Risk factors of trigger point development include the followings:

1. Muscle injury. Stress on muscles can provoke TrP formation. Even a simple muscle sprain during sports activity can cause MPS. But more commonly, repetitive stress during daily activities or work turns a lot of latent TrPs into active ones.
2. Body asymmetry and poor posture. Biomechanical problems resulting in awkward compensatory body positioning are powerful precipitating factors of MPS. For instance, people with leg-length inequalities are common to have TrPs in their back and pelvic muscles. On the other hand, poor posture can also cause MPS. For example, sitting with the head turned to one side for prolonged period can provoke TrP formation in sternocleidomastoid muscle (one of the large neck muscles) on that side.
3. Inactivity. Prolonged immobilization after surgery or a stroke can turn latent TrPs into active TrPs.
4. Stress and anxiety. People who experience stress and anxiety frequently are more likely to develop TrPs in their muscles. One theory holds that these people may be more likely to clench their muscles, a form of repetitive stress that leaves muscles susceptible to TrP development.
5. Age. MPS is more likely in middle-aged adults. It's thought that younger people's muscles better cope with stress and strain, so they are less susceptible.
6. Sex. Women are more likely than men to experience MPS. The reason is unclear.

Symptoms and signs:

TrPs are either active or latent. Even though latent TrPs are clinically silent with respect to pain, they may cause restriction of movement and weakness of the affected muscles that can be made evident during clinical musculoskeletal examination. However, once a TrP is turned active, it will cause a variety of symptoms including:

• Local pain
• Characteristic referred pain pattern
• Muscle tightness, joint stiffness and limitation of movement
• Local twitch response
• Muscle weakness without atrophy
• Tendon jerks
• Autonomic phenomena such as nausea or dizziness

Interestingly, TrPs are also well-known for its bizarre clinical presentations and should be one of the differential diagnoses for all symptoms with unexplained etiology. For example, a patient with TrP in their neck muscles can present to their doctors with headache or excessive tearing only without the neck pain; a patient with TrP in abdominal muscles can present with unexplained stomachache or pelvic pain despite after sophisticated investigations including endoscopy, laparoscopy and computer tomography.

Diagnosis:

The diagnosis of MPS is always clinical. MPS can be established if a single or multiple taut bands are palpable in the muscles that produce a local and/or characteristic referred pain pattern as well as a local twitch response. At the same time, musculoskeletal physicians will explore the underlying biomechanical and ergonomic causative factors of your MPS.

Treatment:

Treatment of MPS can include a combination of the followings:

• Muscle energy technique
• Spray and stretch release
• TrP injection
• Acupuncture
• Cold, heat, electrical therapy
• Specific home stretching exercises
• Correction of underlying biomechanical problem
• Avoidance of perpetuating and provoking causes to prevent recurrence

激痛點和肌筋膜疼痛綜合症

肌筋膜疼痛綜合症是由肌筋膜內激痛點引發的綜合症，其中包括感覺、運動和自律神經方面的多種症狀。

定義:

肌筋膜疼痛綜合症是由肌筋膜內激痛點引發的綜合症，其中包括感覺、運動和自律神經方面的多種症狀。根據 Travell & Simons 所著的《肌筋膜痛及功能障礙》一書所描述，肌筋膜激痛點是一個超敏感的病灶，通常位於骨骼肌和/或其相關筋膜中的繃緊帶內；其有壓痛，也可產生特徵性轉移痛和自律神經反應現象。

病理生理學:

有多種學說試圖解釋激痛點的形成，其中 Travell 的始動創傷學說認為肌內繃緊帶是形成激痛點的先決條件。繃緊帶也常見於無症狀的人群，一旦繃緊帶形成，便有產生激痛點的風險。風險因素包括：

1. 肌組織損傷. 肌組織上的壓力可激發激痛點的形成。即使運動時肌肉的簡單扭傷也可引起肌筋膜疼痛綜合症。但更常見的是日常生活和工作中的重複性壓力啟動了隱性的激痛點。
2. 身體不對稱和姿勢不良. 生物力學問題導致補償性的姿勢不良是形成肌筋膜疼痛綜合症的重要促發因素，如雙下肢不等長的人多有背部及骨盆肌內的激痛點，長時間頭傾向一邊的坐姿可誘發激痛點形成於同側的胸鎖乳突肌(頸部的一組大肌肉)內。
3. 缺乏活動. 手術或中風後長期臥床可使隱性激痛點轉化為活性激痛點。
4. 緊張和焦慮. 經常緊張和焦慮的人更易產生激痛點。有學說認為這些人的肌肉易處於緊張狀態，形式一種重複性壓力，使肌肉產生激痛點。
5. 年齡. 肌筋膜疼痛綜合症更多見於中年人，因為年輕人的肌肉較易從疲勞中恢復，所以較少產生肌筋膜疼痛綜合症。
6. 性別. 女性較男性多見肌筋膜疼痛綜合症，原因不明。

症狀與表徵:

激痛點可以是活性也可以是隱性的。儘管隱性激痛點不引起疼痛，但臨床作肌骼檢查時可發現受累的肌束活動受限及肌力降低。然而，一旦隱性激痛點被啟動，便會產生多種症狀，包括:

• 局部痛
• 特徵性牽涉痛
• 肌肉收緊，關節僵硬和活動受限
• 局部抽搐反應
• 肌力降低但無肌萎縮
• 腱痙攣
• 自律神經現象，如噁心或頭暈

激痛點的臨床表現是出名的奇特，所以當遇到不能解釋的症狀時，激痛點應作為鑒別診斷之一。例如，頸部肌帶有激痛點的患者可以因頭痛及流淚求診但卻無頸痛的症狀；腹壁肌內激痛點的患者可以因原因不明的胃痛或盆腔痛求診，但經過詳細檢查包括胃鏡、腹腔鏡和電腦掃描仍無法解釋病因。

診斷:

肌筋膜疼痛綜合症的診斷通常都是臨床的。若在肌內觸到一條或多條繃緊帶，並由此產生局部觸痛和/或特徵性轉移痛以及局部抽搐反應，便可診斷為肌筋膜疼痛綜合症。肌骼科醫生同時還會找出其致病的生物力學和環境因素。

治療:

治療肌筋膜疼痛綜合症可結合以下幾方面:

• 肌能量法
• 噴劑和拉伸放鬆法
• 激痛點注射法
• 針灸
• 冷療、熱療、電療法
• 自我拉伸練習
• 糾正潛在的生物力學因素
• 避免誘發和刺激因素以防復發