Short communicationThe effects of the interthalamic adhesion position on cerebrospinal fluid dynamics in the cerebral ventricles
Introduction
The cerebral ventricle is the main route for cerebrospinal fluid (CSF) to flow from within the brain to the subarachnoid space. According to phase-contrast cine magnetic resonance (MR) imaging studies, CSF flows in a pulsatile manner in the cerebral ventricles and its source of pulsation is related to the increase in cerebral blood flow during cardiac systole. The increase in blood flow in the cranium during systole results in expansion of the brain parenchyma and causes slight compression of the lateral ventricles. During systole, CSF flows from the lateral ventricle to the third ventricle through the foramen of Monroe (Feinberg and Mark, 1987; Enzmann and Pelc, 1991). It then flows from the third ventricle to the cerebral aqueduct and exits after the fourth ventricle. During diastole, CSF flow reverses and flows back towards the lateral ventricle.
The third ventricle has a complex geometry, as part of its cavity is fused by the medial border of the left and right thalamus. This anatomical feature is known as interthalamic adhesion (massa intermedia) and is found in approximately 80% of humans. Interestingly, the location of the interthalamic adhesion is highly variable, and its size may be related to the formation of congenital anomalies such as Arnold-Chiari malformation and meningomyelocele (Cooding et al., 1967; Naidich et al., 1980).
The functional implications of the interthalamic adhesion and how it influences CSF dynamics in the cerebral ventricular system remain unclear. In this study, we present 4 three-dimensional computational models of the cerebral ventricles with the interthalamic adhesion modeled at different locations in the third ventricle. We hypothesize that the interthalamic adhesion influences the pattern of CSF recirculation and the level of pressure in the third ventricle. The aim of this study was to emphasize the importance of modeling this anatomical feature and investigate whether its location may increase the susceptibility of developing hydrocephalus.
Section snippets
Reconstruction and meshing of the cerebral ventricles
A three-dimensional model of the third ventricle and the cerebral aqueduct were reconstructed based on a series of coronal and axial images of a human from a magnetic resonance imaging scan. This was achieved by first manually outlining the cross section of the ventricle and aqueduct in each image to obtain the volumetric spline representation (Surfdriver, version 3.5). These splines were then exported to modeling software (Rhinoceros, version 3, McNeel, USA, Seattle) where the surfaces of the
Results
At the beginning of the cardiac cycle, CSF flows from the foramen of Monroe to the cerebral aqueduct and exits after the fourth ventricle. At 25% of the cardiac cycle, the direction of the CSF flow reverses and recirculation is observed in the third ventricle in all the models except for the second model. Fig. 2 shows that the region of recirculation (indicated by *) is different in all of the models. At 25% of the cardiac cycle, two CSF recirculation zones can be observed in model I. One of
Discussion
The location of the interthalamic adhesion was found to play an important role in the distribution of CSF pressure in the third ventricle. In addition, its location influences CSF flow dynamics and the location of fluid recirculation in different regions of the third ventricle at different times of the cardiac cycle. Recirculation occurs when there is a change in CSF flow direction and is dependent on the individual CSF flow characteristics (in the third ventricle) that precede it. Results from
Conflict of interest
No conflicts of interest to declare.
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