Corneal confocal microscopy identifies small nerve fibre damage in patients with isolated mesh associated pain syndrome

Introduction Surgery using polypropylene mesh devices was the gold-standard procedure for stress urinary incontinence (SUI). Use of vaginally placed mesh devices has been restricted due to rising rates of complications of which pain is the most prevalent. The aetiology of Isolated Mesh Associated Pain Syndrome (I-MAPS) remains elusive. There is growing evidence to support the involvement of a neuropathically-mediated process with the possibility of systemic effects. Objectives To objectively identify small nerve fibre injury in patients with I-MAPS and correlate this against women with painless devices and a healthy control group. Study design Forty-six women with continence mesh devices were enrolled of which 26 had I-MAPS and 22 were pain-free. These were compared against 22 healthy, mesh and pain-free controls. Participants underwent nerve fibre assessment using Corneal Confocal Microscopy (CCM), Including Corneal Nerve Fibre Density (CNFD), Corneal Nerve Branch Density (CNBD) and Corneal Nerve Fibre Length (CNFL). Neuropathic pain was assessed using the Pain DETECT questionnaire (PDQ). Functional and mental well-being was ascertained using the EuroQol 5-Dimension (EQ5D) and WHO-5 wellbeing questionnaires. Results Women with I-MAPS had significant reductions in corneal nerve fibre health across all 3 morphological parameters compared to pain-free women with mesh and healthy pain and mesh-free controls. This included CNFD (15.85 ± 4.23 vs. 27.46 ± 6.84 fibres/mm 2 , p < 0.0001) (15.85 ± 4.23 vs. 29.43 ± 6.30 fibres/mm 2 , p < 0.0001), CNBD (14.77 ± 6.69 vs. 32.41 ± 14.53 branches/mm 2 , p = 0.0002) (14.77 ± 6.69 vs. 39.68 ± 18.92 branches/mm 2 , p < 0.0001) and CNFL (9.88 ± 2.49 vs. 15.67 ± 3.41 mm/mm 2 , p < 0.0001) (9.88 ± 2.49 vs. 17.21 ± 3.46 mm/mm 2 , p < 0.0001). Conclusions Small nerve fibre injury potentially contributes to the symptomatology of I-MAPS and may highlight a systemic effect of polypropylene mesh implants. These findings warrant further investigation in larger study groups.