Scientific Session 01 — SS01: Neuroradiology - Head, Neck, and SpineMonday, May 6, 2019
1226. The Interpeduncular Angle: A Practical and Objective Marker For Detection and Diagnosis of Intracranial Hypotension on Brain MRI
Wang D1,2*, Pandey S1,2, Lee D1,2, Sharma M1,2 1. Western University, London, Canada; 2. London Health Sciences Centre, London, Canada
Address correspondence to D. Wang (email@example.com)
Objective: Findings of intracranial hypotension on MRI, such as brainstem slumping, can be subtle, bringing subjective variability and potentially making the diagnosis difficult. Therefore, a more objective measurement can be valuable. We hypothesize that the angle between the cerebral peduncles will correlate with the volume of interpeduncular cistern fluid, and thus, will be decreased in cases of intracranial hypotension. We aim to investigate its use as a practical and objective measurement for MRI detection of intracranial hypotension.
Materials and Methods: We retrospectively selected patients with a clinical diagnosis of intracranial hypotension and age-matched controls. Clinical data including presenting symptoms and response to treatment were reviewed. MRI images were reviewed by two fellowship-trained radiologists from our institution to assess for classical findings of intracranial hypotension, including subdural collections, brainstem slumping, pachymeningeal thickening or enhancement, and venous engorgement. The interpeduncular angle was measured on routine axial T2 images and analyzed between groups with Student’s t-test. ROC analysis was performed to identify an ideal angle threshold to maximize sensitivity and specificity. Interobserver reliability was assessed for classical findings of intracranial hypotension by use of Cohen’s kappa value and the interpeduncular angle with intraclass correlation.
Results: Thirty patients with intracranial hypotension and 30 controls were examined. The most common clinical presentation was headache (88% in the study group and 78% in the control group). Pachymeningeal thickening or enhancement was the most sensitive sign of intracranial hypotension (86.7%). The average interpeduncular angle was significantly lower in the study group than in the control group (25.3 degrees vs 56.3 degrees; p < 0.0005). Significant correlation was found between the interpeduncular angle and the presence of brainstem slumping (p < 0.0005) as well as severe cases, defined as having 3 or more classical features of intracranial hypotension (p = 0.013). ROC analysis for the interpeduncular angle demonstrated an area under the curve of 0.92. With a threshold of 40 degrees, sensitivity for the test was 80% and specificity was 96.7%. Excellent interobserver reliability for the interpeduncular angle was shown (ICC value = 0.833).
Conclusion: The interpeduncular angle is an easily and reliably measurable parameter on routine clinical MRI scans for detection and diagnosis of intracranial hypotension, with high sensitivity and specificity. It serves not only as a good adjunct marker in classical cases but can also be the first detectable sign in subtle cases. The narrowed interpeduncular angle may reflect a decrease in basal cisternal fluid and may serve as an objective proxy for brainstem slumping, a hypothesis supported by its significant correlation with brainstem slumping and with severe cases of intracranial hypotension.