An incidental persistent falcine sinus with dominant straight sinus and hypoplastic distal superior sagittal sinus.

An incidental persistent falcine sinus was detected in an otherwise normal brain on MRI in a 12-year-old girl who underwent imaging after clinical suspicion of acute disseminated encephalomyelitis. The falcine sinus was associated with a hypoplastic posterior third of the superior sagittal sinus and a dominant straight sinus. Generally, atresia or hypoplasia of the straight sinus is associated with a persistent falcine sinus in postnatal life; otherwise, the falcine sinus disappears before birth. We discuss the embryological basis for such an association in this case.