Accuracy of MRI CSF Flowmetry in the Diagnosis of Normal Pressure Hydrocephalus

Abstract

BACKGROUND: Normal pressure hydrocephalus (NPH) is one of the few treatable causes of dementia. NPH is diagnosed using the clinical triad of: Gait disturbance, progressive mental deterioration, urinary urgency, or incontinence in association with radiological findings suggestive of NPH, for example, ventriculomegaly, disproportionately enlarged subarachnoid space hydrocephalus, and narrow callosal angles. AIM: The purpose of the present study was to assess the accuracy of MRI cine phase flow studies as a non-invasive modality in the diagnosis, and also for the prediction of improvement of symptoms suggestive of NPH without the need for CSF tapping. METHODS: Twenty-six patients suffering clinically from the triad of NPH, or at least two of them; attending our neurology, psychiatry, and neurosurgery clinics in Cairo University Hospitals, with ages ranging between 50 and 85 years, randomly chosen regarding sex or other comorbidities. All patients underwent a regular MRI in addition to CSF flowmetry studies to correlate the MRI findings that reveal NPH with their known clinical features. Careful clinical assessment was performed to detect severity of symptoms, and patients were classified accordingly, and a disability score was provided. After CSF tapping, patients were reassessed clinically after 6–8 h to detect improvement of symptoms, and the degree of improvement was compared to the result of CSF flow study. RESULTS: CSF flow studies, particularly stroke volume across the aqueduct of Sylvius, provide the highest significance in diagnosing hyperdynamic circulation evident by many radiological studies in cases of NPH. This was also found to be a good prognostic factor which correlates well with the improvement of symptoms following CSF tapping. However, its use to exclude suspicious cases of NPH seems unreliable, that is, not a good negative predictor. Findings of MRI CSF flow studies also show significance in detecting brain atrophic changes, especially peak systolic velocity, which usually accompany or mimic the clinical picture of NPH. CONCLUSION: MRI CSF flow studies are an excellent aid as an adjuvant non-invasive technique in selection of suspicious cases as it shows significance in detecting hyperdynamic circulation, especially high stroke volume results in cases of NPH. Both CSF tapping and CSF flowmetry findings “low stroke volume values” were not found to be a good negative predictor for clinical improvement after shunting.