Subdural fluid accumulation caused by ventriculoperitoneal shunt underdrainage: A rare and paradoxical complication

Background Subdural fluid collection in patients with internal cerebrospinal fluid (CSF) shunts has generally been linked to overdrainage and more rarely to pus accumulation. The authors present a previously unrecognized condition leading to extra-axial CSF accumulation: shunt underdrainage. Treatment of coexisting subdural fluid collection and hydrocephalus, disorders that have previously only been reported concurrently following head trauma or subarachnoid hemorrhage, is controversial. In addition, we intend to provide insight into the physiopathology of abnormal CSF accumulation within both the subdural space and ventricles simultaneously. Case description A 42-year-old female with a history of hypothalamic glioma and obstructive hydrocephalus during childhood presented with headache, vomiting, and gait disturbance. Following the insertion of her first ventriculoperitoneal shunt (VPS) by the age of 8, she underwent several surgeries due to shunt failure, all of them associating ventriculomegaly. Ventricles remained notably enlarged following insertion of her most recent VPS, and the computed tomography scan performed 2 months later at her admission showed a large subdural collection. Afterward, a malpositioned distal catheter causing shunt blockage was confirmed. Both, the subdural accumulation and hydrocephalus, were resolved following adequate placement of the peritoneal catheter. Conclusion This case demonstrates that subdural fluid accumulations may occur following VPS underdrainage with hydrocephalus. Development of such extra-axial collection was probably caused by pressure related to CSF spillage from the ventricles into the subdural space. Our case also supports that a mass-effect subdural accumulation with hydrocephalus can be satisfactorily treated with adequate VPS alone, without directly treating the subdural collection.