Reversible tactile hypoesthesia associated with myofascial trigger points: a pilot study on prevalence and clinical implications

Abstract

Introduction: Tactile hypoesthesia observed in patients with myofascial pain syndrome (MPS) is sometimes reversible when pain is relieved by trigger point injections (TPIs). We aimed to investigate the prevalence of such reversible hypoesthesia during TPI therapy and topographical relations between areas of tactile hypoesthesia and myofascial trigger points (MTrP) in patients with MPS.

Methods: Forty-six consecutive patients with MTrP were enrolled in this study. We closely observed changes in areas of tactile hypoesthesia in patients who had tactile hypoesthesia at the first visit, and throughout TPI therapy. Tactile stimulation was given using cotton swabs, and the areas of tactile hypoesthesia were delineated with an aqueous marker and recorded in photographs.

Results: A reduction in the size of hypoesthetic area with TPI was observed in 27 (58.7%) patients. All the 27 patients experienced a reduction in pain intensity by more than 50% in a numerical rating scale score through TPI therapy. In 9 patients, the reduction in the sizes of hypoesthetic areas occurred 10 minutes after TPI. Complete disappearance of tactile hypoesthesia after TPI therapy was observed in 6 of the 27 patients. Myofascial trigger points were located in the muscles in the vicinity of ipsilateral cutaneous dermatomes to which the hypoesthetic areas belonged.

Conclusion: Our results indicate a relatively high prevalence of reversible tactile hypoesthesia in patients with MPS. Mapping of tactile hypoesthetic areas seems clinically useful for detecting MTrP. In addition, treating MTrP with TPI may be important for distinguishing tactile hypoesthesia associated with MPS from that with neuropathic pain.

Keywords: Muscle pain; Myofascial pain syndrome; Tactile sensory abnormalities; Touch; Trigger point injection.

Figure 1.

Identification of MTrP and delineation of tactile hypoesthesia areas. Tactile hypoesthesia and MTrP observed in a 41-year-old female patient at the first visit are shown in A and B. She was referred to our pain clinic due to head (occipital) and neck pain lasting 7 months with a NRS score of 7 to 8/10, after negative findings in both CT and myelography. At the first visit (A), she had severe MTrP (X) in the right trapezius muscle and tactile hypoesthesia around the right shoulder (delineated with a blue line). Ten minutes after TPI to MTrP, there was a reduction in the size of the tactile hypoesthesia (B). She was treated in 3 sessions of TPI over 3 weeks and concomitant oral medications with nortriptyline and acetaminophen for 4 weeks. Two weeks later at the second visit, the tactile hypoesthesia had already disappeared (C) along with decrease of pain with an NRS of 5/10 before the second TPI. The NRS became 2/10 or less at 4 weeks after consultation. Left: photograph. Right: tactile hypoesthesia and MTrP depicted on 3-D dermatomes. MrTP, myofascial trigger points; NRS, numerical rating scale.

Figure 2.

Reduction in the size of tactile hypoesthesia in association with a decrease of myofascial pain by TPI: A typical case. A 63-year-old male patient was referred to our pain clinic with complaints of severe right lateral chest pain. He had no pathological findings such as rib fractures in CT, nor abnormal laboratory data. At the first visit, we found an area of tactile hypoesthesia of 20 cm × 11 cm with an NRS score (degree of hypoesthesia) of 5/10, and MTrP of external oblique muscles (A, the left photographs). Ten minutes after TPI, the hypoesthetic area reduced in its size as shown in A with arrows (the right photograph). He was treated with a total of 8 sessions of TPI with a concomitant oral medication of nortriptyline for 10 weeks. Progressive reductions in the size of hypoesthetic area were observed in parallel with decreases in pain intensity, during TPI therapy (A–E, the left side of photographs and 3-D dermatomes). Note that the areas of tactile hypoesthesia were round or oval and changed plastically without following the dermatomal distribution. MrTP, myofascial trigger points; NRS, numerical rating scale.