A case control study was conducted on 30 patients confirmed to have IIH according to the modified Dandy criteria [7] at the Neurology Department. These patients were either first discovered to have IIH or in a regular follow-up at our outpatients’ clinic. All are females with age range from 18 to 42 years. Ten patients were already on medical treatment only (group II), ten cases were on medical treatment and frequent lumbar tapping (group III) with regular follow-up at our outpatient clinic for 2 consecutive years, and other ten cases were diagnosed with IIH recently but had not yet started any medications (group I). Ten healthy female subjects were subjected to our study as a control with age range from 23 to 41 years (group IV). All patients underwent detailed history, full neurological examination, fundus examination, measurement of CSF opening pressure by lumbar puncture, neuro-imaging, and other laboratory findings. The study received approval from the Institutional Review Board, Faculty of Medicine, with code number MS/17.07.13. Informed consents were obtained from all participants in the study.
We recruited patients with IIH according to diagnostic criteria for pseudotumor cerebri syndrome [8]: (1) papilloedema, (2) normal neurologic examination except for cranial nerve abnormalities, (3) neuroimaging: normal brain parenchyma without evidence of hydrocephalus, mass, or structural lesion and no abnormal meningeal enhancement and magnetic resonance venography for others, (4) normal CSF composition, (5) elevated lumbar puncture opening pressure (> 250 mm H2O).
Those patients who had abnormal magnetic resonance imaging (MRI) findings of space-occupying lesions, hydrocephalus, meningitis, or subarachnoid hemorrhage were excluded from this study. Also, those who had normal CSF pressure or had disc edema from other causes as ischemic optic neuropathy and diabetic papillopathy were excluded from the study. Finally, patients who had contraindication for MRI were excluded from the study such as: presence of cardiac pacemaker or those who had electrically or magnetically activated implants (cochlear implants).
The study was conducted on a 1.5-T MRI scanner (Ingenia, Philips Healthcare 1.5 T S E) using a circular polarized head coil. CSF flow dynamic quantitative study was performed using high-resolution axial phase-contrast protocol with imaging phase perpendicular to cerebral aqueduct. A cine acquisition with sensitivity to velocity in the section-select direction was obtained. The direction of flow encoding was caudocranial. The acquired raw data were interpolated to produce 16 frames equally spaced in the cardiac cycle by means of an MRI-compatible peripheral pulse transducer applied to the subject’s finger with retrospective cardiac gating that means MR data are acquired continuously (not in response to a particular cardiorespiratory “trigger” event).
After the data acquisition, all images were transferred to the workstation equipment with the Q flow software that permits quantification of flow-related physiologic data like CSF. A region of interest was drawn manually to include all pixels that reflected the CSF flow signals of the aqueduct on the phase images after magnification of the images to clarify the aqueduct, after that the CSF flow parameters were automatically extracted.
Firstly, the images were analyzed qualitatively using midsagittal phase and magnitude images which revealed aqueductal CSF flow in both systole and diastole; caudal flow in systole was represented as hyperintense signal, while the diastolic flow (cranial flow) was represented as hypointense signal; the change of flow in the aqueduct during systole and diastole ruled out the presence of aqueductal obstruction [9].
For quantitative assessment, peak systolic and diastolic velocities were extracted from the mean velocity time curve. CSF flow dynamics were analyzed in terms of peak diastolic velocity (PDV) in centimeter per second, peak systolic velocity (PSV) in centimeter per second, and aqueductal area. Aqueductal stroke volume was calculated by summation of forward and backward flow, multiplied by duration of CSF flow. The mean flow (MF) was calculated by multiplying the mean velocity in centimeter per second by the aqueductal area in square centimeters where the mean velocity was automatically determined from the mean value of the measured velocities of each cardiac cycle [10].
Statistical analysis
Data were fed to the computer and analyzed using IBM Statistical Package for Social Sciences (SPSS) software package version 22.0 [11]. Qualitative data were described as numbers and percentages using Chi-square test and Monte Carlo test. Quantitative data were described using mean ± standard deviation (SD) for parametric data using Student’s t test and one way analysis of variance (ANOVA) test. Significance of the obtained results was judged at the (0.05) level. The accuracy of a test to discriminate diseased cases from non-diseased cases is evaluated using receiver operating characteristic (ROC) curve analysis. Sensitivity and specificity were detected from the curve; positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated through cross tabulation.
