Etiology- and region-specific characteristics of transependymal cerebrospinal fluid flow

OBJECTIVE Transependymal flow (TEF) of CSF, often delineated as T2-weighted hyperintensity adjacent to the lateral ventricles on MRI, is a known imaging finding, usually in the setting of CSF flow disturbances. Specific radiological features of TEF and their relationships with clinical markers of hydrocephalus and underlying disease pathology are not known. Here, the authors describe the radiological features and clinical associations of TEF with implications for CSF circulation in the setting of intracranial pathology. METHODS After obtaining IRB review and approval, the authors reviewed the radiological records of all patients who underwent intracranial imaging with CT or MRI at St. Louis Children’s Hospital, St. Louis, Missouri, between 2008 and 2019 to identify individuals with TEF. Then, under direct review of imaging, TEF pattern, degree, and location and underlying pathology and other radiological and clinical features pertaining to CSF circulation and CSF disturbances were noted. RESULTS TEF of CSF was identified in 219 patients and was most prevalent in the setting of neoplasms (72%). In 69% of the overall cohort, TEF was seen adjacent to the anterior aspect of the frontal horns and the posterior aspect of the occipital horns of the lateral ventricles, and nearly half of these patients also had TEF dorsal to the third ventricle near the splenium of the corpus callosum. This pattern was independently associated with posterior fossa medulloblastoma when compared with pilocytic astrocytoma (OR 4.75, 95% CI 1.43–18.53, p = 0.0157). Patients with congenital or neonatal-onset hydrocephalus accounted for 13% of patients and were more likely to have TEF circumferentially around the ventricles without the fronto-occipital distribution. Patients who ultimately required permanent CSF diversion surgery were more likely to have the circumferential TEF pattern, a smaller degree of TEF, and a lack of papilledema at the time of CSF diversion surgery. CONCLUSIONS CSF transmigration across the ependyma is usually restricted to specific periventricular regions and is etiology specific. Certain radiological TEF characteristics are associated with tumor pathology and may reflect impaired or preserved ependymal fluid handling and global CSF circulation. These findings have implications for TEF as a disease-specific marker and in understanding CSF handling within the brain.