The Neurotoxicity of Epidural Hyaluronic Acid in Rabbits: A Light and Electron Microscopic Examination

Because hyaluronic acid (HA) has an antiinflammatory effect and prevents and/or reduces tissue adhesion, we believed it possible that epidurally-administered HA during epidural adhesiolysis procedures could alleviate pain in patients with chronic lower back pain. Therefore, we performed this pre-clinical trial evaluation of epidurally-administered HA neurotoxicity by light microscopy (LM) and electron microscopy (EM) in rabbits. Twenty rabbits were randomly divided into two groups, a normal saline (NS) group (n = 10) and a HA group (n = 10). Saline (0.2 mL/kg of 0.9% solution) and the same volume of HA were injected into the epidural space. No rabbits showed any sensory-motor or behavior change during the 3-wk period, except for one rabbit in the NS group that showed decreased appetite, activity, and weight loss. By LM, two rabbits in the NS group showed abnormal findings considered to be the result of trauma and infection associated with epidural catheterization. EM findings showed no significant neurotoxic findings in either group. In conclusion, epidurally-admmistered HA did not cause neurotoxicity in rabbits.