American Journal of Neuroradiology 29:215-216, February 2008
© 2008 American Society of Neuroradiology
Letter
Reply:
a Department of Neuroradiology
University of Schleswig-Holstein Campus Kiel
Kiel, Germany
Because venous sinus stenoses in idiopathic intracranial hypertension (IIH) can be reversed by lowering the intracranial pressure, I believe that these stenoses are caused primarily by elevated intracranial pressure. I think there might, furthermore, be a feedback mechanism in IIH such that an increase in intracranial pressure (due to impaired absorption of CSF?) leads to stenoses of the transverse sinuses and that these stenoses lead to an increase in intravenous pressure proximal to the stenoses (which can be measured directly by a catheter). This again could hamper absorption of CSF, leading to a further increase in pressure. (In theory, pressure would then rise infinitely, but in reality it does not. Therefore, the mechanisms must be somewhat more complex.) We saw cases of secondary intracranial hypertension demonstrating narrowing of large segments of the intracranial sinuses, whereas in IIH, there seems to be a predilection for the development of the stenoses in the lateral parts of the transverse sinuses. Therefore, patients with IIH probably have some pathoanatomic change in this region of the sinus ("vulnerable segments" may be secondary to hormonal changes).
I agree with Bateman that patients might profit from stent angioplasty, which interrupts the feedback mechanism. However, the problem is—as he stated and as our first patient demonstrated—that stent angioplasty might be necessary for all the "vulnerable" segments of the intracranial sinuses. Moreover, we probably tackle only a part of the problem with this procedure. On the other hand, there might be a subgroup of patients with IIH who have fixed sinus stenoses (eg, originating in venous sinus thrombosis) predisposing them for stent angioplasty. We have to prove though that these groups of patients really exist.
I also think there is a need for a randomized controlled multicenter trial in which the performance of stent angioplasty versus shunt surgery procedures is compared in patients with pharmacoresistant IIH. In such a study, subgroups of patients with fixed and reversible stenoses should be analyzed separately. Until then, I do not favor performing stent angioplasty in patients with reversible stenoses.
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