[A Rare Case of Communicating Hydrocephalus with Intraparenchymal Pericatheter Cyst and Surrounding Edema in an Adult due to Accidental Change in the Pressure Setting of the Programmable Shunt System]

A 59-year-old woman suffering from memory impairment visited our hospital. She was discharged nine years ago without complications after undergoing neck clipping surgery for intracranial aneurysm rupture and a right ventricular peritoneal shunt using the CODMAN^® HAKIM^® programmable valve system(CHPV)for hydrocephalus. Initial CT/MRI revealed a cystic lesion with surrounding edema in the right frontal lobe around the proximal catheter, and a left frontal subacute subdural hematoma. The right ventricle was shown as a slit as before. The cystic portion presented with an MRI signal of the same intensity as the cerebrospinal fluid(CSF), and no enhancement effect was observed. It was thought to be a CSF cyst around the shunt catheter with interstitial CSF edema. Skull radiographs showed an accidental change in the CHPV pressure setting(100 to 190mmH₂O), possibly due to head impact. We concluded that the newly set valve pressure caused sudden shunt dysfunction, resulting in CSF cyst formation and surrounding edema. Image findings and her symptoms were immediately improved on adjusting the shunt valve. This complication in adults associated with shunt dysfunction is very rare and only 10 cases have been reported to date. This is the first report of this complication due to an accidental reset of CHPV. To prevent the risk of misdiagnosing this condition as a tumor or abscess and performing unnecessary surgery, it is always necessary to suspect the possibility of this complication. For that purpose, detailed images, including diffusion-weighted images and contrast-enhanced MRI, should be done early in clinical practice.