Introduction: In patients with Intracranial Hypotension Syndrome (IHS), we observed reduction of the angle between vein of the Galen (VOG) and internal cerebral vein (ICV), which returns to the baseline after treatment. We coin the term "venous hinge" to describe this dynamic process and discuss its importance in IHS.
Methods: A midsagittal T1W image showing both VOG and ICV in the same plane was retrospectively analyzed by three different neuroradiologists in 17 patients with IHS. The angle between the lines drawn along the main axis of VOG and ICV (venous hinge angle (VHA)) was measured and documented. This angle measured from the magnetic resonance imaging (MRI) of the 50 normal controls was also recorded. Paired t tests were used to compare the VHA between male and female controls and between patients of IHS and normal controls. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated. The VHA was also calculated after treatment of these patients and paired t test was done to look for significant change in the VHA after treatment.
Results: The mean VHA formed by the veins in the IHS and control groups were 65 degrees (35-98 degrees) and 91 degrees (76-124 degrees) respectively (P < 0.0001). At a VHA of 79 degrees, the sensitivity, specificity, PPV, and NPV for diagnosis of IHS were 88.24%, 92%, 78.95%, and 95.83% respectively. In ten patients, follow-up MRI demonstrated normalization of the collapsing angle following appropriate treatment (p = 0.003).
Conclusion: We report a previously undescribed imaging finding in patients with IHS. Recognition of this sign may aid in the diagnosis of IHS.