Craniectomy-associated Progressive Extra-Axial Collections with Treated Hydrocephalus (CAPECTH): redefining a common complication of decompressive craniectomy.

Extra-axial fluid collections following decompressive craniectomy have been observed in a variety of patient populations. These collections have traditionally been thought to represent extra-axial signs of hydrocephalus, but they often occur even in settings where hydrocephalus has been optimally treated. This study aims to elucidate the phenomenon of extra-axial fluid collections after decompressive craniectomy in patients with treated hydrocephalus, in order to improve identification, classification, prevention and treatment. We retrospectively reviewed all patients at a single institution undergoing decompressive craniectomy for refractory intracranial pressure elevations from June 2007 through December 2009. We identified 39 patients by reviewing clinical reports and imaging. Any patient who died on or prior to the third post-operative day (POD) was excluded. The analysis focused on patients with extra-axial collections and treated hydrocephalus. Twenty-one of 34 (62%) patients developed extra-axial collections and 18 of these developed collections despite ventricular drainage. Subgroup analysis revealed that seven of seven patients (100%) with subarachnoid hemorrhage, and 11 of 14 (79%) with traumatic brain injury developed collections. Extra-axial collections may develop after decompressive craniectomy despite aggressive treatment of communicating hydrocephalus. In these patients, the term "external hydrocephalus" does not appropriately capture the relevant pathophysiology. Instead, we define a new phenomenon, "Craniectomy-associated Progressive Extra-Axial Collections with Treated Hydrocephalus" (CAPECTH), as progressive collections despite aggressive cerebral spinal fluid (CSF) drainage. Our data indicate that early cranioplasty can help prevent the formation and worsening of this condition, presumably by returning normal CSF dynamics.