The Effect of Topical Anesthesia on Pain Perception in Patients with Local Myalgia

Abstract: Temporomandibular disorders (TMD) is a term used to embrace pain and dysfunction in the jaw-, face- and temple region. Myofascial pain is considered the most common condition included in TMD. The diagnostic criteria for myalgia are based on the patient’s symptoms and clinical signs, where pain to palpation of the jaw muscles is vital. The aim of this experimental trial was to examine whether pain perception is influenced by topical anesthesia in patients with local myalgia of the jaw muscles. Our hypothesis was that the pressure pain thresholds (PPT) at jaw muscle sites are affected after topical application of anesthesia in patients with local myalgia. Ten women (median age 36 years) with TMD related to myalgia participated in the study. The PPT at masseter muscle and temporal muscle sites bilaterally and the first dorsal intraossei on the dominant hand were measured using an electronic algometer. After a baseline registration, EMLA or placebo cream was applied on the chosen sites in a randomized order. A new registration was carried out five minutes after the application. The values for each participant before and after the application were compared using Wilcoxon rank sum test. A P-value < 0.05 was considered statistically significant. The PPT increased significantly after application of topical anesthesia, but not placebo cream. The results indicate that the superficial nociceptors were sensitized and sensitive to topical anesthesia in patients with TMD related to myalgia. The interpretation of a pain response to pressure thus seems to be complex and warrant further studies.