Hypothesis for intracranial hypertension in slit ventricle syndrome: new concept of capillary absorption laziness in the hydrocephalic patients with long-term shunts.

Many theories have been postulated to date regarding mechanisms involved in intracranial hypertension in patients with long-term, shunt-induced slit ventricle syndrome (SVS), but it still seems difficult to define this entity more clearly. Many hypotheses have attempted to explain the causes of SVS as chronic or intermittent catheter obstruction, brain compliance change, and ventricular herniation and distortion, but this theory does not explain clearly the reason why extraventricular pressure (EVP) is increased and intraventricular pressure (IVP) is low or frequently negative. The authors attempt to postulate a hypothesis by addressing new concept of capillary absorption laziness which results in dissociation of EVP with IVP. We, the authors, propose a concept of 'capillary absorption laziness', which is a tendency of the brain parenchymal extracellular fluid (ECF) not to be absorbed through the brain parenchymal capillary absorption system (BPCAS) that results from the bypass of ECF to shunt in the low or even negative ECF pressure and IVP. If this continues for a prolonged period, the tendency not to be absorbed through the BPCAS, even when the IVP and extracellular fluid pressures increases more than the intracranial pressure (ICP), may be established. This leads to situations of the brain such as parenchymal accumulation of the ECF which results in brain edema or swelling, and eventually distortion or herniation which can act as a functional obstruction and consequent dissociation between the IVP and EVP. Hypothesis of capillary absorption laziness may explain several common phenomena of the SVS such as low or even negative IVP in coexistence with high EVP and high ICP, and in these cases, we expect serious complications of SVS such as brain distortion and herniation. From this hypothesis we attempt to find new shunt management protocols to prevent long-term shunt induced complications.