Falcine Sinus: Incidence and Imaging Characteristics of Three-Dimensional Contrast-Enhanced Thin-Section Magnetic Resonance Imaging

Objective: To evaluate the incidence, characteristics, and variations of the falcine sinus with contrast-enhanced three-dimentional (3D) thin-section magnetic resonance (MR) images. Materials and Methods: A retrospective review identified 1531 patients (745 males and 786 females, 2 months to 85 years) who underwent cranial MR imaging including T1-weighted imaging, T2-weighted imaging, T2-weighted fluid-attenuated inversion recovery, contrast-enhanced 3D thin-section sagittal scans, and MR venography, from June 2014 to January 2016. The incidence, characteristics of the falcine sinus, and coexisted intracranial lesions were confirmed by two neuroradiologists. Results: Falcine sinuses were identified in 81 (38 males and 43 females) cases (5.3%, 81/1531, 5 months to 76 years of age) with calibers ranging from 2.3 mm to 17.0 mm. Three major forms of falcine sinuses were defined: arch-like (n = 47), stick-like (n = 22), and bifurcated (n = 12). Persistent falcine sinuses were found in 57 cases, among which 3 cases showed complicated cerebral anomalies, and 2 cases showed smaller straight sinuses. Recanalization of falcine sinuses were found in 24 cases, including 17 cases with tumor compression, 6 cases with cerebral venous sinus thrombosis, and one case with hypertrophic meningitis. Conclusion: Falcine sinus is not as rare as has been reported previously. Most falcine sinuses are not associated with congenital cerebral abnormalities. Diseases that cause increased pressure in the venous sinus may lead to recanalization of falcine sinus. Illustrating the characteristics of falcine sinus may prompt a more comprehensive understanding and diagnosis of associated diseases, and avoid potential surgical damage in the future.