P eriventricular lucency (PVL) refers to the decreased attenuation level, or "blurring," around the periventricular area on CT, or T2 hyperintensity on MRI. This radiological phenomenon is a common finding not only in various neurological or cardiovascular disorders, but also in the general elderly population. 21,22,29,47 Although widely researched and documented, the pathogenesis and clinical significance of PVL are still inconclusive, especially for PVL associated with hydrocephalus. Hydrocephalus is defined as the excessive accumulation of CSF in the brain due to various causes. The disease is considered to be caused by an imbalance between the formation and reabsorption of CSF, due to the disturbance in CSF dynamics. 28 Considering the site of the obstruction in the flow of CSF, two types of hydrocephalus have been defined: communicating and noncommunicating. PVL in hydrocephalus was first documented by Naidich et al. 27PVL and enlarged ventricles are typical radiological signs of acute or noncommunicating hydrocephalus.30 However, these two signs also exist in chronic or communicating hydrocephalus, although the prevalence is relatively lower. 25,34 In either case, the pathogenesis of PVL remains abbreviatioNs FE = finite element; ICP = intracranial pressure; ISF = interstitial fluid; PVL = periventricular lucency; TPG = transmantle pressure gradient. obJective Periventricular lucency (PVL) is often observed in the hydrocephalic brain on CT or MRI. Earlier studies have proposed the extravasation of ventricular CSF into the periventricular white matter or transependymal CSF absorption as possible causes of PVL in hydrocephalus. However, there is insufficient evidence for either theory to be conclusive. methods A finite element (FE) model of the hydrocephalic brain with detailed anatomical geometry was constructed to investigate the possible mechanism of PVL in hydrocephalus. The initiation of hydrocephalus was modeled by applying a transmantle pressure gradient (TPG). The model was exposed to varying TPGs to investigate the effects of different geometrical characteristics on the distribution of PVL. The edema map was derived based on the interstitial pore pressure. results The model simulated the main radiological features of hydrocephalus, i.e., ventriculomegaly and PVL. The degree of PVL, assessed by the pore pressure, was prominent in mild to moderate ventriculomegaly. As the degree of ventriculomegaly exceeded certain values, the pore pressure across the cerebrum became positive, thus inducing the disappearance of PVL. coNclusioNs The results are in accordance with common clinical findings of PVL. The degree of ventriculomegaly significantly influences the development of PVL, but two factors were not linearly correlated. The results are indicative of the transependymal CSF absorption as a possible cause of PVL, but the extravasation theory cannot be formally rejected.

The model simulates all the clinical features in correlation with the MR images obtained in patients with hydrocephalus and IIH, thus providing support for the role of the transmantle pressure gradient and capillary CSF absorption in CSF-related brain deformation. The finite element methods can be used for a better understanding of the pathophysiological mechanisms of neurological disorders associated with parenchymal volumetric fluctuation.

Hydrocephalus and idiopathic intracranial hypertension (IIH) are neuropathies associated with disturbed cerebrospinal fluid dynamics. Several finite element (FE) brain models were suggested to simulate the pathological changes in hydrocephalus, but with overly simplified assumptions regarding the properties of the brain parenchyma. This study proposes a two-dimensional FE brain model, capable of simulating both hydrocephalus and IIH by incorporating poro-hyperelasticity of the brain and detailed structural information (i.e., sulci).