- BACKGROUND AND PURPOSE: The IJVs are considered to be the main pathway draining the intracranial venous system. There is increasing evidence for the existence of alternative venous pathways. Studies using extracranial sonography techniques have demonstrated a nonjugular venous system. In the current study, we used MR images to investigate the NJV drainage system and its components (vertebral plexus, pterygopalatine plexus). The exact visualization and measurement of the intracranial NJVs could be of diagnostic importance and may have clinical importance. MATERIALS AND METHODS: A total of 64 participants with no history of neurologic disease were included in the study. All participants underwent scanning with a 2D time-of-flight, multisection sequence in the supine position. Image processing software was developed to identify and quantify the size of the IJVs and NJVs in the plane of the internal JF. For evaluation of software accuracy, all images were reviewed by a neuroradiologist experienced in neurovascular imaging preprocessing and postprocessing. RESULTS: The CSA of the NJVs correlated inversely with the CSA of the IJVs ( r 2 = 0.25; P r 2 = 0.19; P = .0004; pterygopalatine plexus: r 2 = 0.11; P = .0069). Furthermore, only NJV cumulative CSA correlated inversely with participant age ( r 2 = 0.2; P = .0002). CONCLUSIONS: Our study indicates that the NJVs might serve as a compensatory drainage mechanism in the intracranial compartment. This mechanism appears less significant as the age of the patient progresses.