Physical Medicine and Rehabilitation for Myofascial Pain Workup

Updated: May 21, 2017
  • Author: Jennifer E Finley, MD, FAAPMR; Chief Editor: Dean H Hommer, MD  more...
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Workup

Laboratory Studies

No specific lab tests confirm a diagnosis of myofascial pain (MP), but lab tests can be helpful in looking for predisposing conditions, such as hypothyroidism, hypoglycemia, and vitamin deficiencies. Specific tests that may be helpful include complete blood count (CBC), chemistry profile, erythrocyte sedimentation rate (ESR), and levels of vitamins C, B-1, B-6, B-12, and folic acid. A thyrotropin level may be helpful if clinical features of thyroid disease are present.

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Imaging Studies

Infrared or liquid crystal thermography can show increased blood flow, which is sometimes noted at trigger points. Other imaging studies are useful only to rule out other sources of pain generation.

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Other Tests

Needle electromyography (EMG) examination of trigger points (TrPs) in humans and rabbits has shown high-voltage spike activity and spontaneous, low-voltage endplate noise, which is considered characteristic but not pathognomonic. Surface EMG has been used in experiment protocols to monitor muscle activity in TrPs. Ultrasonography has been used to visualize the LTR elicited by needle penetration.

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Procedures

Trigger point (TrP) injections sometimes are performed with bupivacaine, etidocaine, lidocaine, saline, or sterile water. [11, 12, 13, 14] Dry needling is occasionally performed, without the injection of any substance. [15, 16]

TrP injection results are better if an LTR can be elicited. Ultrasound guidance can be helpful for recognition of LTR in deeper muscles, but is not helpful in finding TrPs. [17]

Botulinum toxin (BOTOX®) shows promise as a substance that can provide long-lasting relief. [18, 19, 20, 21] Its mechanism of action may be related to the blocking of acetylcholine release at the neuromuscular junction of the dysfunctional motor endplates.

A retrospective study by Avendaño-Coy et al indicated that in combination with physical therapy, intramuscular injections with botulinum toxin type A (BoNT-A) are effective against MP syndrome. The study, which involved the records of 301 patients with persistent MP syndrome, found that at 6 months, positive results were achieved with this treatment combination in 58.1% of patients, including 82.9% of those with primary MP syndrome and 54.9% of those with secondary MP syndrome. The effectiveness of therapy in the latter group was influenced by the disorders associated with secondary MP syndrome. [22]

A report by Affaitati et al indicated that a topical anesthetic patch can also relieve myofascial pain, without the discomfort that can result from TrP injections. [23] Patients in the study were separated into groups of 20, one of which was treated for 4 days with a lidocaine patch applied to each patient's trigger point (with patients receiving a total daily dose of 350 mg). The second group received a placebo patch, and the third group was treated with injections of 0.5% bupivacaine hydrochloride.

In members of the lidocaine patch and bupivacaine injection groups, the investigators found significant decreases and increases in, respectively, subjective symptoms and pain thresholds. Although the effects at muscle TrPs and target areas were more pronounced in the injected patients, the lidocaine patients experienced less therapy-related discomfort. Subjective symptoms and pain thresholds did not improve in the placebo group.

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Histologic Findings

Contraction knots are a characteristic finding in trigger points, and tender, palpable nodules have been recognized since 1951.

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