Falcine sinus and occipital encephalocele: a magnetic resonance venographystudy

Object. Occipital encephaloceles are relatively frequently encountered Many investigators have addressed the embryogenesis of these formations, but th e dural system has never before been studied. In this retrospective analysi s the authors sought to gain a better understanding of the origins of these defects. Methods. The charts and radiological examinations, especially the magnetic resonance venography studies, were reviewed in seven patients. In six patie nts the straight sinus was absent. Drainage of the galenic system took plac e through a sinus within the falx, also known as a falcine sinus. The tento rium was not seen in five patients. Conclusions. The combination of an absent straight sinus and dysplastic ten torium is no coincidence: both develop within the same mesenchyme in the me sencephalic flexure. Distortion of the mesenchyme by a neural tube defect, causing an occipital encephalocele, will lead not only to disorders of the tentorium but also of the straight sinus.