Intracranial granuloma: a rare long-term complication of retained shunt catheter. Illustrative case.

BACKGROUND: Ventriculoperitoneal shunt placement is the most commonly used treatment for hydrocephalus. However, its malfunction frequently presents a challenge in clinical practice, necessitating shunt revision. In certain instances, intracranial catheter revision may pose difficulties due to severe intraluminal adhesions, necessitating the surgeon to leave the catheter in situ. However, retained catheters can lead to severe complications. OBSERVATIONS: A 17-year-old male presented with headache and unsteady gait for several weeks. He had a cystoperitoneal shunt for hydrocephalus associated with Dandy-Walker malformation during infancy. However, at the age of 12 years, the shunt was found to be nonfunctioning and was removed, except for the intradural catheter, due to severe adhesions. Brain MRI revealed a large mass encasing the catheter. Craniotomy and gross-total resection of the mass, including the catheter, revealed a granuloma, but no organisms were isolated from the specimen. The postoperative recovery was uneventful, and there was no recurrence for 10 years. LESSONS: This case highlights a potential complication associated with retained intracranial catheters and their neurosurgical management. Our literature review identified a limited number of comparable cases of retained catheter-related granuloma, and the pathophysiology and treatment were elucidated within the review. https://thejns.org/doi/10.3171/CASE25557.