The measurement of CSF flow through the aqueduct in normal and hydrocephalic children: from where does it come, to where does it go?

Despite 100 years of study, the theories of cerebrospinal fluid (CSF) formation and absorption remain controversial. Measuring CSF flow through the aqueduct using magnetic resonance imaging (MRI) provides a unique insight into the physiology of CSF hydrodynamics. The published data in adults tend to refute rather than support the prevailing theories of CSF flow. There are limited data regarding this metric in children. This paper seeks to measure the aqueduct flow in normal and hydrocephalic children to help formulate a more complete theory of CSF flow.

Twenty-four children with communicating hydrocephalus aged from 4 months to 16 years underwent MRI flow quantification of the aqueduct measuring the net flow. The patients were compared to 19 controls.

The controls revealed two different flow patterns: (1) an infantile pattern characterized by flow directed into the ventricular system and (2) a mature pattern with flow directed out of the ventricles, similar to the published findings in adults. In infants with communicating hydrocephalus, the aqueduct flow changed direction but was of similar magnitude compared with the controls (p = 0.001). In the older hydrocephalic children, the flow was elevated 7-fold, but the direction was unchanged compared to the controls (p = 0.002).

There is an abrupt change in the aqueduct CSF flow pattern at the age of 2 years from an infantile pattern to a mature pattern. These findings together with the findings in hydrocephalic children do not support the current theories of CSF hydrodynamics. A new theory of CSF circulation based on capillary absorption is presented.