Why do inguinal hernia patients have pain? Histology points to compression neuropathy

The purpose of this study is to describe the known soft tissue neuro-histology factors associated with compression neuropathy in relation to the incidence of preoperative pain in primary inguinal hernia. Enlargement of the ilioinguinal nerve occurs in 63% of patients with primary inguinal hernia; compression neuropathy has similar gross features.

Patients completed pain questionnaires pertaining to preoperative pain and the quality of pain experienced. During routine inguinal hernia repair, nerve segments were sampled for histologic evaluation.

Twenty-two thickened nerve segments (63% of total) with proximal and distal specimens were resected for examination and comparison. We quantified various histologic indicators including nerve diameter, fascicle count, myxoid content within the epineurium, perineurium and endoneurium. Increased preoperative patient pain scores correlate with increased nerve diameter, increased fascicle count and increased myxoid material both within the perineurium and endoneurium.

These findings support the concept that preoperative hernia pain is associated with compression neuropathy.