Cerebrospinal fluid is an ultra-filtrate of plasma which circulates in the subarachnoid space, located between the pia and arachnoid maters. It is mainly produced by the choroid plexuses, while lesser amount produced by the ependymal cells lining the ventricles. The function of the CSF includes cushioning and lubrication of the central nervous system, circulation of nutrients and waste collection.
The aim of our study was to determine the value of cine phase contrast MRI in characterizing CSF flow in patients presenting with changes in normal CSF flow dynamics which is divided into two groups the first one for those presented with dementia, gait disturbance and urinary incontinence to differentiate NPH from involutional brain changes and the second are fore those presented hydrocephalus either communicating or non-communicating, Our study population included 74 patients, 51 case with overlapping symptoms of normal pressure hydrocephalus versus involutional brain changes ,23 cases of obstructive and communicating hydrocephalus.
The protocol of examination used to assess CSF flow dynamics at the level of the aqueduct of Sylvius both quantitatively using an axial imaging plane perpendicular to the aqueduct and qualitatively with a sagittal in plane assessment and for certain circumstances at the level of foramen magnum.
The control population included 9 healthy volunteers that were examined according to this protocol. Phase contrast cine MR flow imaging provides a simple way to better characterize CSF flow. The application of cine phase-contrast MRI technique in patients with NPH holds great promise for improvement of the diagnosis, especially in those cases where the differentiation from atrophy on clinical and conventional radiological basis is difficult. In the normal patient, consistent flow patterns are observed and are quite different from those patterns that are seen in CSF flow disorders.
The information obtained by cine phase-contrast MRI is often not apparent on routinely acquired MR images and may help to answer the question of whether the ventriculomegaly observed on routine MR is associated with patent or obstructed CSF pathways and to determine the exact level of obstruction.
In NPH cases, CSF diversionary procedure gives great results and improves the condition, a cine phase contrast MR may provide valuable evidence that such surgery is indicated or not as it provides a mapping of CSF velocity and measures the CSF stroke volume in any region of interest along the CSF pathway. So cine phase contrast MR imaging provides the potential for non-invasive CSF flow quantification,
The patients of hydrocephalus could be examined by CT or conventional MR determining the level and cause yet the CSF drive (heavy T2) added high resolution image for differentiation CSF from surrounding tissue ,detecting any obstructing agent even thin septations or web ,cine phase Quantitive and qualitative assessment helped the understand of flow dynamic ,evaluating the flow across the aqueduct and foramen magnum helping choice of surgical or conservative treatment ,it also helped the assessment of spontaneous ventriculostomy and evaluation post-operative cases .
Considerable information on the physiology of the normal CSF circulation is gained from the results of these measurements and it permits the reassessment of our understanding of human physiology. We, indeed observed that in normal individuals, the normal to and fro movement of the CSF flow could be qualitatively appreciated in the aqueduct, foramen of Magendie, and in the dorsal and ventral subarachnoid space at the cervico-medullary junction: . during CSF mid systole, there is caudal flow in all CSF spaces. During CSF diastole, there is cranial flow in all CSF spaces.
Pathological CSF flow dynamics in normal pressure hydrocephalus, The systolic peak velocity and the systolic stroke volume values were statistically significantly higher than those of the normal controls, these results indicate that patients with normal pressure hydrocephalus have hyper dynamic aqueductal CSF flow.
In cerebral atrophy, blood flow to the brain is decreased; we found lower systolic peak velocity, systolic mean velocity and stroke volume values in comparison to healthy volunteers indicating a hypo dynamic CSF circulation. This should allow for exclusion of other patients with similar symptomatology resulting in dementia caused by vascular, toxic or other causes. So Increased CSF mean and peak velocities above the normal values strongly suggest NPH, on the other hand if these values are decreased; this favors the diagnosis of atrophy.
In communicating hydrocephalus ,flow is assessed showing free passage of CSF ,peak systolic velocity and stroke volume showed variable values being hyper dynamic ,hypo dynamic and normal ,which helps the treatment choice
In obstructive hydrocephalus ,flow is assessed showing obstructed passage of CSF evaluating the etiology and degree ,peak systolic velocity and stroke volume showed variable values being hyper dynamic ,hypo dynamic or absent and normal ,which helps the treatment choice
IN CONCLUSION, assessments of CSF flow as described and illustrated before indicate the potentials of using phase contrast imaging for quantitative and qualitative CSF flow analysis. It is a useful adjunct to routine MR for clinical study of CSF related diseases as well as for CSF physiology research, and as an aid for differential diagnosis in certain conditions. In our opinion all patients was suspected, or diagnosed obstructive or communicating (including NPH) should be examined by MR CSF Flowmetry.
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