Objectives We report an unusual presentation of reversible methotrexate (MTX) induced leukoencephalopathy due to a malfunctioning Ommaya reservoir. A subacute presentation of hemiplegia and encephalopathy alerted to the possibility of device malfunction. Expedited reservoir removal and corticosteroids resulted in neurological recovery. We hope to highlight the importance of considering MTX toxicity and Ommaya reservoir device malfunction in patients who receive intrathecal treatment.

Methods A case report describes the evolution of leukoencephalopathy after an instillation of MTX through an Ommaya reservoir. Prior reports suggest direct chemotherapy toxicity from back flow of CSF along the catheter, due to obstruction or malfunctioning devices.

Case A 67-year-old woman with breast cancer carcinomatous meningitis developed subacute onset left sided hemiplegia and impaired sensorium, three days after her last instillation of 12 mg MTX through an Ommaya reservoir. The device was inserted through the right frontal cortex and had four prior MTX instillations (45 mg MTX total) without any reported complications. There was no trauma to the device or changes in the chemotherapy administration protocols. MRI showed a 24 mm×16 mm×27 mm fluid collection in the right sub cortical matter with extensive white matter increased T2 signal change with sulcal and ventricular effacement. Prompt recognition warranted intravenous steroid administration and subsequent reservoir and catheter removal. CSF demonstrated aseptic meningitis. A brain biopsy demonstrated inflammatory changes with reactive gliosis and some haemorrhage. No evidence of malignancy. Testing of the removed Ommaya reservoir ex-vivo demonstrated a small leak from the underside of the reservoir, suggesting needle penetration through the base of the reservoir. The patient made a good clinical recovery and returned home.

Conclusions This report illustrates an unusual presentation of reversible MTX leuknoencephalopathy due to Ommaya reservoir malfunction. Early clinical review and imaging post instillation of chemotherapy through the Ommaya reservoir maybe beneficial to detect early complications.