Visualisation of cerebrospinal fluid flow patterns in albino Xenopus larvae in vivo

The development of Xenopus larval brain ventricles and the patterns of CSF flow were visualised after injection of quantum dot nanocrystals and polystyrene beads (3.1 or 5.8 μm in diameter) into the fourth cerebral ventricle at embryonic/larval stages 30-53.The fluorescent nanocrystals showed the normal development of the cerebral ventricles from embryonic/larval stages 38 to 53. The polystyrene beads injected into stage 47-49 larvae revealed three CSF flow patterns, left-handed, right-handed and non-biased, in movement of the beads into the third ventricle from the cerebral aqueduct (aqueduct of Sylvius). In the lateral ventricles, anterior to the third ventricle, CSF flow moved anteriorly along the outer wall of the ventricle to the inner wall and then posteriorly, creating a semicircle. In the cerebral aqueduct, connecting the third and fourth cerebral ventricles, CSF flow moved rostrally in the dorsal region and caudally in the ventral region. Also in the fourth ventricle, clear dorso-ventral differences in fluid flow pattern were observed.This is the first visualisation of the orchestrated CSF flow pattern in developing vertebrates using a live animal imaging approach. CSF flow in Xenopus albino larvae showed a largely consistent pattern, with the exception of individual differences in left-right asymmetrical flow in the third ventricle.Early investigators studied the role of cerebrospinal fluid (CSF) flow and observed that CSF flow is generated by a balance of fluid dynamics between the CSF pressure and CSF absorption by tissues [1]. More recently, the use of magnetic resonance imaging (MRI) revealed that ciliary movement induces a constant CSF flow in humans [2-4]. Previous investigators also reported the ciliary action of ependymal cells in amphibians [5]. Abnormal CSF flow causes various diseases in mammals, such as communicating hydrocephalus in humans where the CSF flow differs from that of healthy individuals [6-9]. These observations suggest that contin