An attempt to develop a model to study the effects of intrathecal steroids

An attempt has been made to develop a chronic inflammatory arachnoiditis model in the rat to study the influence of subarachnoid or epidural steroids. Through chronically implanted catheters in Wistar rats (250-350 g), either triamcinolone (3.5-350 micrograms) or methylprednisolone (3.5-350 micrograms) was injected intrathecally, daily for 7 days or weekly for 7 weeks. Some rats also received 100 mg kg-1 cefoxitin and 0.5 mg deoxycortone by intramuscular injection. Equivalent control groups were included. High doses of intrathecal steroids caused marked weight loss and infection and many rats died. These effects were mitigated at a lower dosage especially by the addition of cefoxitin and deoxycortone. The effects of triamcinolone were more marked than those of methylprednisolone. No systematic histological evidence of neurotoxicity was observed after either steroid. Injections of talc failed to cause arachnoiditis or meningitis probably because sufficient particulate talc could not be injected through the narrow catheter.