A venographic cryptic stenosis at the junction of middle and lateral third of the transverse sinus has been observed in patients suffering from idiopathic intracranial hypertension. After reviewing the anatomical and embryological literature of the transverse sinus, 20 transverse sinuses were explored (in a pilot study of 10 human cadavers) in order to determine the anatomical basis of this stenosis. The presence of septa of varying sizes was observed. We conclude that the presence of a large septum is one of the causes of venographic cryptic stenosis observed in these patients and might be one of the aetiological factors involved in idiopathic intracranial hypertension.