Intramedullary catheter penetration and compressive granuloma from a high-dose intrathecal pain pump: illustrative case

BACKGROUND: Catheter-tip granulomas are a rare complication of intrathecal drug delivery systems, typically associated with high opioid concentrations and usually forming in the intradural extramedullary space. Intramedullary catheter penetration is exceedingly uncommon and may accelerate neurological decline due to cord injury and increased local drug exposure. OBSERVATIONS: A 43-year-old woman with multiple prior spine surgeries and an intrathecal pain pump presented with 8 months of progressive thoracic myelopathy, sensory loss, gait spasticity, and functional decline. MRI demonstrated a rim-enhancing intradural extramedullary mass at T9 causing cord compression with associated edema. Operative exploration revealed a large granuloma spanning T9-10 with the catheter tip embedded in the lesion and penetrating the spinal cord. Microsurgical granuloma resection, catheter extraction, laminoplasty, and device explantation were performed without neuromonitoring changes. The patient experienced postoperative neurological improvement. LESSONS: Intramedullary catheter malposition is a rare but serious mechanism of catheter-tip granuloma formation and should be suspected in patients with progressive myelopathy following pump revision or escalating intrathecal dosing. Early MRI evaluation, prompt surgical decompression, and precise catheter removal are critical for preventing permanent neurological deficits. This case highlights the need for vigilance during intrathecal pump management and recognition of atypical catheter positioning as a driver of compressive granuloma formation. https://thejns.org/doi/10.3171/CASE26362.