MRI AND CSF FLOW DYNAMICS IN EVALUATION OF PEDIATRIC HYDROCEPHALUS

Abstract

Over the past decade, MR CSF evaluation has evolved from the visual qualitative technique (Bradley WG et a/, 1991) into an indispensable quantitative technique, offering the clinician diagnostic and prognostic information for a variety of conditions of which diagnostic imaging can be of little help. With careful consideration and evaluation of the subarachnoid space with cine phase-contrast techniques, flow abnormalities can be detected. These alterations in CSF flow appear to play a significant role in diagnosis of communicating hydrocephalus, They may also be helpful in determining the clinical significance of findings such as arachnoid cysts and Chiari I malformation, and are helpful in evaluating and determining the patency of third ventriculostomies. This technique has already played a major role in the noninvasive study of CSF flow dynamics. (Kizziar Ret a/, 2000)

The production and flow of human cerebrospinal fluid (CSF) has been studied since 'Ie 1940s,however, early investigations were hampered by a lack of noninvasive studies. Magnetic resonance (MR) investigation in CSF flow began with the qualitative observation of the degree of flow void in the aqueduct of Sylvius and adjacent third and fourth ventricles. Although this early MR method was useful in the evaluation of patients with suspected NPH, the clinical success was limited and this observational method was not significantly used because the presence of flow-void phenomenon in the aqueduct is a qualitative measure, which is influenced by many acquisition parameters, and often may be difficult to quantifY. Phase-contrast cine MR flow imaging provides a simple way to better characterize CSF flow. By applying Phase-contrast CSF velocity imaging both the magnitude (speed) and direction along any axis can be determined, it is far more sensitive to areas of slower CSF flow than is magnitude imaging. As a result, phase­ contrast imaging can identifY flow in the basal cisterns when such flow is not apparent on magnitude imaging. (Kizziar Ret a/, 2000), (Quencer RM, 1992)

The application of erne phase-contrast MRI technique m hydrocephalic children holds great promise for improved diagnosis, particularly in those cases where the exact level or levels of CSF obstruction need to be determined In the normal patient. consistent flow patterns are observed and are quite different from those patterns that are seen in