Local Anesthetic Injections for the Short-Term Treatment of Head and Neck Myofascial Pain Syndrome: A Systematic Review with Meta-Analysis

Myofascial pain syndrome (MPS) affects 13.8% of the US population, with the head, neck, and shoulders being the most common sites. This condition is characterized by deep aching pain arising from trigger points—tender spots in muscle bands that reproduce the patient's pain when pressed. While trigger point injections are considered one of the most effective treatments, it remains unclear whether using local anesthetics provides additional benefits over dry needling (needling without medication). This systematic review aimed to determine whether local anesthetic injections are more effective than dry needling, placebo treatments, or other interventions for head and neck myofascial pain.

The researchers conducted a comprehensive search of four major medical databases through April 2018, finding 324 initial references. After screening, they included 15 randomized controlled trials involving 884 adult patients diagnosed with myofascial pain syndrome. The studies compared local anesthetics (primarily lidocaine 0.5-2% or procaine 1%) to dry needling, saline placebo injections, or other treatments. The primary outcome was pain intensity measured on a 0-10 visual analog scale.

They also examined secondary outcomes including pressure pain thresholds, range of motion, and depression scores. The researchers performed separate meta-analyses for different comparison groups and conducted sensitivity analyses to test the reliability of their findings.

When all studies were included, local anesthetic injections showed a statistically significant pain reduction of 1.585 points compared to dry needling at 1-4 weeks (p = 0.020). However, this advantage disappeared when only high-quality, double-blinded studies were analyzed, with no significant difference found (p = 0.331). Compared to placebo injections, local anesthetics showed a smaller but significant improvement of 0.767 points (p = 0.007). Subgroup analyses revealed that studies with higher bias risk were more likely to show benefits for local anesthetics, and studies that included home exercises showed better results than those without.

No significant differences were found in pressure pain thresholds, range of motion, or depression scores. Adverse effects were generally mild, including soreness, burning sensation, and occasional dizziness.

This review provides only low-quality evidence supporting local anesthetic injections over dry needling for head and neck trigger points. The difference may not be clinically meaningful, and the apparent benefit might be due to study bias or accompanying home treatments rather than the medication itself. For patients, this suggests that dry needling alone may be just as effective as injections with local anesthetics, potentially avoiding the small risks and costs associated with medications. For clinicians, these findings support current practice guidelines that recommend starting with less invasive treatments.

The results highlight the need for larger, well-designed studies with better blinding and standardized protocols to definitively determine whether local anesthetics provide meaningful benefits over dry needling for myofascial trigger points.