Idiopathic intracranial hypertension: priapism of the brain?

It has long been recognized that a clinical syndrome similar to idiopathic intracranial hypertension can occur secondary to venous sinus obstruction with the elevation in sinus pressure causing a reversal in the pressure gradient across the arachnoid granulations and therefore elevated CSF pressure. There remains, however, a group of predominantly obese female patients with elevated CSF pressures who have either no apparent abnormality of venous outflow or a tapering, apparently extrinsic compression, of their dominant transverse sinuses on catheter venography. This suggests that venous collapse may be associated in some way with the cause of the elevated pressure but clearly something else must be initiating the pressure rise or a circular argument ensues. Elevated CSF pressure compresses the veins, which then elevates CSF pressure. However, collapse of the venous sinuses secondary to the elevated CSF pressure once initiated may exacerbate the condition. It has been suggested that the initiating event leading to the elevated pressures in the idiopathic group of patients may be caused by cerebral hyperaemia and cerebral dysautoregulation. Priapism is a condition of pathological elevation of venous pressure of the male genitalia in which there are two forms: (1) venous out flow obstruction and (2) hyperaemia due to a to loss of regulation of blood flow and secondary venous out flow compression. Review of the literature suggests the pathophysiology of idiopathic intracranial hypertension may be analogous to that of priapism.