Axon Loss and Collagen Deposition Confirms Compression Neuropathy in the Ilioinguinal Nerve Resected From Primary Inguinal Herniorrhaphy Patients.

Introduction: Prior studies show pre-operative pain in primary inguinal hernia patients is associated with visible enlargement of the ilioinguinal nerve at the external ring. However, the ilioinguinal nerve has not been previously examined for evidence of axon loss in conjunction with inguinal hernia. This study investigates axon loss and collagen deposition in the ilioinguinal nerve as evidence of compression neuropathy associated with primary inguinal hernias. Methods: Ten male patients with visible ilioinguinal nerve enlargement during primary inguinal herniorrhaphies were enrolled in this prospective study. Resected nerve samples included the proximal (control), canal, and distal segments relative to the external ring. Epoxy resin sections were stained with toluidine blue to assess axon loss, and paraffin sections were stained with trichrome stains to evaluate collagen content. Results: Moderate to severe axon loss was observed in the canal and distal segments in 70% and 80% of patients, respectively. The canal segment demonstrated a significant increase in collagen content when compared to the proximal control (p < 0.02). Fascicular cross-sectional area increased significantly in canal and distal segments compared to control (p < 0.0058, p < 0.0098). The total nerve area of the canal segment was significantly smaller compared to the proximal control and distal segment (p < 0.006, p < 0.04). Discussion: In patients with primary inguinal hernias, the exposure of the ilioinguinal nerve within the canal segment can be associated with moderate to severe axon loss and increased fascicular areas due to collagen fibrosis, consistent with compression neuropathy.