Comparative study of nerve fiber density between adenomyosis patients with moderate to severe pain and mild pain

Background: Since some retrospective studies have given inconsistent findings about innervation in adenomyosis, its role in the pain mechanism is still inconclusive. Objective: Define the nerve fiber density in adenomyotic tissue as it correlated to pain symptoms.

Material and Method: A cross-sectional study was performed in twenty-five uterine samples from reproductive age women with adenomyosis who underwent either laparotomy or laparoscopic surgery. The nerve fiber density from hysterectomized specimens as measured by immunohistochemistry staining for Protein gene product (PGP) 9.5 and Neurofilament (NF) were compared with the level of pain in the patients as defined by a visual analogue scale and a verbal rating scale.

Results: Nerve fibers as detected by PGP9.5 and NF staining in the myometrium were significantly increased in the group of women with adenomyosis experiencing moderate and severe pain as compared to the group experiencing less pain (4 (0, 7) vs. 1.55 (0, 7)/mm², p-value <0.001, and 6 (3, 10) vs. 0 (0, 4)/mm², p-value <0.001 respectively). At both phases of the menstrual cycle, the densities of nerve fibers stained with PGP9.5 and NF showed no significant difference. Conclusion: These results suggested that the increased of nerve fibers shown in the more severe pain group might play a role in the pathogenesis or symptoms of adenomyosis.