CSF Flow in the Brain in the Context of Normal Pressure Hydrocephalus

Abstract

SUMMARY: CSF normally flows back and forth through the aqueduct during the cardiac cycle. During systole, the brain and intracranial vasculature expand and compress the lateral and third ventricles, forcing CSF craniocaudad. During diastole, they contract and flow through the aqueduct reverses. Hyperdynamic CSF flow through the aqueduct is seen when there is ventricular enlargement without cerebral atrophy. Therefore, patients presenting with clinical normal pressure hydrocephalus who have hyperdynamic CSF flow have been found to respond better to ventriculoperitoneal shunting than those with normal or decreased CSF flow. Patients with normal pressure hydrocephalus have also been found to have larger intracranial volumes than sex-matched controls, suggesting that they may have had benign external hydrocephalus as infants. While their arachnoidal granulations clearly have decreased CSF resorptive capacity, it now appears that this is fixed and that the arachnoidal granulations are not merely immature. Such patients appear to develop a parallel pathway for CSF to exit the ventricles through the extracellular space of the brain and the venous side of the glymphatic system. This pathway remains functional until late adulthood when the patient develops deep white matter ischemia, which is characterized histologically by myelin pallor (ie, loss of lipid). The attraction between the bare myelin protein and the CSF increases resistance to the extracellular outflow of CSF, causing it to back up, resulting in hydrocephalus. Thus idiopathic normal pressure hydrocephalus appears to be a "2 hit" disease: benign external hydrocephalus in infancy followed by deep white matter ischemia in late adulthood. ABBREVIATIONS:ACSV ϭ aqueductal CSF stroke volume; DESH ϭ disproportionately enlarged subarachnoid space hydrocephalus; DWMI ϭ deep white matter

Choroidal fissure acts as an overflow device in cerebrospinal fluid drainage: morphological comparison between idiopathic and secondary normal-pressure hydrocephalus

“…Furthermore, current research suggests that lymphatic drainage via the peri- and para-vascular space233137383940, perineural subarachnoid spaces of the cranial nerves or meninges25264142 is the major pathway for absorption of CSF and interstitial fluid, and venous drainage via the dural arachnoid villi is the minor23242843. Newly developed MRI techniques for assessing CSF dynamics have revealed that CSF moves in a pulsatile fashion and not in a unidirectional bulk flow44454647484950. CSF moves upward and downward around the cranio-cervical junction with cardiac pulsation and respiration as driving forces44454647484950.…”

“…Newly developed MRI techniques for assessing CSF dynamics have revealed that CSF moves in a pulsatile fashion and not in a unidirectional bulk flow44454647484950. CSF moves upward and downward around the cranio-cervical junction with cardiac pulsation and respiration as driving forces44454647484950. These recent findings have negated the classical concept of the CSF bulk flow from the ventricles to subarachnoid spaces through the foramina of Luschka and Magendie.…”

Diffusion imaging of reversible and irreversible microstructural changes within the corticospinal tract in idiopathic normal pressure hydrocephalus

“…The reported prevalence is 0.51–2.9% in the elderly population (Miyajima et al, 2016). The symptoms of iNPH can be improved by surgery to create a ventriculo-peritoneal or lumbo-peritoneal cerebrospinal fluid (CSF) shunt (Kazui et al, 2015, Miyajima et al, 2016), especially in the early stage of the disease (Bradley, 2015). However, the reported degree of improvement has varied widely among different case series (Halperin et al, 2015, Poca et al, 2005, Solana et al, 2012).…”

Quantifying the influence of respiration and cardiac pulsations on cerebrospinal fluid dynamics using real‐time phase‐contrast MRI

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