Hyperbaric oxygen therapy attenuates neuropathic hyperalgesia in rats and idiopathic trigeminal neuralgia in patients

Background: Neuropathic pain after nerve injury is severe and intrac table, and current drug and non-drug therapies offer very limited pain relief.Hyperbaric oxygen (HBO2) has been clinically used for protection of thenervous system after acute injury. We investigated whether HBO2 treatmentcould prevent and/or attenuate neuropathic pain in animals and in patients.Methods: Mechanical allodynia and thermal hyperalgesia and neuro chemical alterations of neuropathic pain were analysed in male, adult,Sprague-Dawley rats with sciatic nerve injury. Clinical trials were con ducted in patients with idiopathic trigeminal neuralgia.Results: Repetitive HBO2 treatment [a combination of pressure at 3 atmo sphere absolute (ATA) and pure oxygen] greatly inhibited behavioural signsof neuropathic pain manifested as thermal hyperalgesia and mechanicalallodynia. Such an HBO2 treatment also inhibited nerve injury-induced induction of c-Fos and activation of astrocytes and increased phosphoryla tion of NR2B receptor and the subsequent Ca2+-dependent signals in rats.Neither high pressure (up to 3 ATA) nor pure oxygen alone resulted in analgesic effect. In clinical trials, one course of HBO2 therapy (10 consecu tive days) produced a rapid-onset, dose-dependent and long-lasting anal gesic effects evidenced by the decreased doses of carbamazepine required for keeping patient pain at a minimum and decreased scores of visual analogue scales, which was used for patient’s self-evaluation.Conclusions: These findings support that HBO2 therapy is an effective approach for treating neuropathic pain in both animals and human beings and suggest that neural protection, anti-inflammation and inhibition of nerve injury-induced altered neural activity may contribute to the analgesic effect of HBO2 therapy