Abstract

Introduction: Long term back pain has been treated with intrathecal drug delivery since 1970. Formation of inflammatory masses at the tips of intrathecal catheters are a known complication and can result in permanent neurologic consequences. Our case represents an uncommon intramedullary granuloma at the T10 level from a morphine pain pump.

Methods: Imaging was acquired using a 3 Tesla MRI scanner (GE HDx, software 14.M5) with spinal 8 channel phase array coils (USA Instruments). Key imaging included pre-contrast axial 3 mm T1 and T2-weighted images, sagittal 5 mm T1, T2 and STIR images, post contrast (20 ml of Multihance gadolinium, IV) axial and sagittal T1-weighted images and high resolution, non-contrast 3D sagittal 3 mm T2-weighted images.

Results: A 43-year-old man with increasing chronic low back pain presented to the ER with additional leg weakness and anterior thigh paresthesias. Physical examination revealed thoracic point tenderness, no skin findings and a normal gait. An outside hospital report described a possible cord mass vs a granuloma. The patient was referred for a neurosurgical evaluation and an MRI of the spine was obtained. An intrathecal catheter entered at the L2 level and extended cephalad to T10. An enhancing mass was located around the distal catheter tip, with enhancement and T2 hyperintensity within the adjacent intramedullary cord. Abnormal high T2 cord signal and generalized cord swelling extended from the T6-T12 levels. Surgical catheter retraction to the T12/L1 interspace and medication dose reduction by 10% resulted in partial resolution of imaging findings. The patient’s symptoms improved on follow-up.

Discussion: Proposed explanations for granuloma formation include abnormal CSF dynamics, catheter positioning and medication-induced inflammation. Histologically, these granulomas are highly vascular, have a peripheral margin of inflammatory cells surrounding a central area of necrosis, and originate from the arachnoid and possibly the dural layers.