Differentiating the disorders. In 1990, the American College of Rheumatology developed criteria for the diagnosis of fibromyalgia, a condition that can sometimes be confused with MPS. MPS can be distinguished from fibromyalgia in a number of ways (table 1).
|Feature||Trigger Points of|
Myofascial Pain Syndrome
|Tender Points of|
|Tender points||Localized||Multiple, generalized|
|Taut band||No variation from normal||No variation from normal|
|Twitch response||No variation from normal||Probably normal|
|Referred pain||More frequent||Less frequent|
|Fatigue||Less frequent||More frequent|
|Poor sleep||Less frequent||More frequent|
|Paresthesia||Less frequent||More frequent|
|Headaches||Less frequent||More frequent|
|Irritable bowel||Less frequent||More frequent|
|Sensation of swelling||Less frequent||More frequent|
Some clinicians are skeptical that MPS is a distinct disorder and believe that the condition is a subset of fibromyalgia. The early literature on these conditions uses the two diagnoses interchangeably. Much of the controversy centers around differentiating the "tender points" found in patients with fibromyalgia and the "trigger points" found in patients with MPS. The trigger point may be associated with a local "jump response" or "jump sign." Thus, when physicians palpate the affected muscle, they feel a "knotted" or "doughy" area, and the patient may instinctively recoil or jump when the area is identified. A tender point associated with fibromyalgia may not be detected when palpated and may represent only an area of maximum tenderness within a sore muscle. Tender points are not associated with referred pain patterns, jump signs, or the motor endplates of the muscle-nerve interface.
One study employed clinical experts to perform tender point examinations on three groups of patients. A small number of patients were prediagnosed with either fibromyalgia or MPS. These patients were compared with 80 "healthy" patients. The experts found taut bands of muscle and muscle twitches in both healthy controls and in patients with either of the conditions. A liberal definition of "trigger points" by these investigators produced overlap between the fibromyalgia group and the MPS group, and local areas of tenderness or "tender spots" were found in both groups.
Muscle Basics, Trigger Points, and Pain Patterns
In MPS, palpating the muscle is painful. The pain is relieved by stretching . This phenomenon is the reason that spray and stretch, local injection, and acupressure—all of which inhibit pain and motor reflex—are employed in treatment as the muscle is stretched to length.
Current theory is that the pain is due to a infection .
Identifying trigger points. The recommended criteria for identifying trigger points consist of essential criteria and confirmatory observations (table 2). Using pain diagrams, examiners can compare patient trigger points identified with those known from published drawings (figure 1).
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