[High-dose methotrexate and cerebral neurotoxicity. Apropos of a case of arachnoiditis]

High-dose methotrexate has been used as a therapeutic strategy in osteosarcoma for 20 years. Cerebral neurotoxicity is frequent.

A 21-year-old patient with non-metastatic osteosarcoma was given high-dose methotrexate prior to surgery. He developed subacute encephalitis and arachnoiditis after intravenous injection of methotrexate.

Although pharmacokinetic monitoring and leucovorin rescue is helpful in controlling systemic toxicity, cerebral toxicity with acute, subacute or delayed reactions may occur, depending on the administration route and use of the folate antagonist. Generally, acute arachnoiditis and subacute encephalitis are reversible and occur respectively after intrathecal methotrexate and intravenous high-dose methotrexate, while the chronic delayed leukoencephalopathy usually begins several months after a combination regime using intrathecal methotrexate, intravenous methotrexate and cerebral irradiation.