Teaching Case

A 14-year-old girl admitted with complaints of fever and headache. An MRI was performed as part of evaluation for meningitis.

Brain MRI was performed on admission. T1-weighted images showed an extra-axial mass in the interhemispheric fissure which was hypointense to grey matter except for a few small T1 hyperintense foci. The lesion is hyperintense on T2-weighted-Fluid-Attenuated Inversion Recovery (FLAIR). Susceptibility weighted imaging (SWI) showed numerous linear and serpiginous hypointense structures coursing towards the hypointense interhemispheric mass.

On sagittal contrast-enhanced venogram and contrast-enhanced T1-weighted images, numerous small veins were noted draining into the intensely enhancing interhemispheric lesion.

The falcine sinus is a normal structure located in the falx cerebri that drains the cerebral venous system to the superior sagittal sinus in the fetus. It usually arises from the vein of Galen or the anterior part of the straight sinus, coursing through the posterior third of the falx cerebri[1]. Persistent falcine sinus after birth has been reported in 2-5% of individuals. It may be associated with other intracranial anomalies, most commonly with vein of Galen aneurysmal malformation in children. Other associated conditions with persistent falcine sinus included corpus callosal dysgenesis, osteogenesis imperfecta, Apert’s syndrome[2].

Falcine sinus may co-exist with other venous anomalies like developmental venous anomalies[3]. Recanalization of falcine sinus is an acquired condition that occurs commonly with tumours like meningioma when the tumour compresses adjacent venous structures, followed by venous thrombosis. Patients may present with complaints of headache due raised intracranial pressure by large tumour or venous thrombosis[4,5]. In the absence of other venous anomalies or tumours, persistent falcine sinus is an incidental finding.

Persistent falcine sinus is more commonly noted in the posterior aspect of interhemispheric fissure. Utilization of thick-slab minimum intensity projections of susceptibility-weighted imaging and contrast-enhanced MR venography to identify the small veins draining into the interhemispheric mass and drainage to the superior or inferior sagittal sinuses helps in identification of this rare anatomical variant[5,6].

The absence of intracranial tumour causing venous compression or venous thrombosis in this patient contributed to the decision to treat the persistent falcine sinus as an incidental imaging finding which warranted no further imaging or treatment. This case report serves to report the rarely noted anterior location of persistent falcine sinus and prevent diagnostic dilemmas.

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