Idiopathic Intracranial Hypertension (IIH)

Today I'm going to be talking to you a little bit about IIH, which is idiopathic intracranial hypertension and the key part of idiopathic intracranial hypertension is that has to be idiopathic. And, there are videos already on IIH so we're not going to be covering that ground. What I want to tell you about is this word idiopathic means that you have exceeded other causes of intracranial hypertension and so that's why I prefer this term idiopathic intracranial hypertension - the alternative term which is pseudotumor cerebri because pseudotumor cerebri just means it's not a tumor. It acts like a tumor but it's not a tumor. And, you can have secondary causes of pseudotumor cerebri that are not idiopathic. And, so when we use that word idiopathic intracranial hypertension there are some conditions that we have to consider even though you have met that modified Dandy criteria. So, as you know in the modified Dandy criteria we have to have symptoms only of increased ICP, we have signs only of increased ICP, we have to have an MRI and an MRV enogram that are negative except for the signs of ICP which is flattening in the globe fluid in the sheath, empty sella, and venous sinus stenosis, usually at the distal transverse sigmoid sinus junction, and we can only have a lumbar puncture that shows increased intracranial pressure of the CSF-content has to be normal. But there are patients who meet these criteria symptoms-signs, radiograph, and spinal tap - that still aren't idiopathic and that's why I prefer the term secondary rather than idiopathic for those patients and the things you want to think about the non-idiopathic category our patients who have had medicines that are associated with increased intracranial pressure. So even though theirs can is going to be normal, their CSF is going to be normal, they have all the symptoms and signs their medicines should be stopped if they are the cause. And so, the most common medicines of course are vitamin A analogues, tetracycline derivatives, but also weird medicines - nalidixic acid, steroids but only steroid withdrawal, and those medicines-and there's a long list of medicines - that have been associated with increased intracranial pressure should be stopped even though technically you met the definition of IH by the modified Dandy criteria. Then there are conditions that are also associated with increased intracranial pressure through a variety of different mechanisms and those patients I would also call secondary I don't like to call them idiopathic. And, there's a whole long list of them but one of the most common is severe anemia, not a regular anemia, but severe anemia patients can have that and in case control studies the anemia is kind of iffy because people that get an anemia are the same people to get pseudotumor cerebri because they're young females who are menstruating and so they're going to have iron deficiency anemia. I'm talking about severe anemia here like after chemotherapy or after blood loss-those kind of patients have a secondary form. And the reason that's important is just transfusing this person or getting their hematocrit up might make their pseudo tumor go away. There are also systemic conditions that are inflammatory like Lupus and Bechet's disease and a whole bunch of inflammatory diseases where we really don't want to be giving idiopathic to these patients because they have a primary diagnosis. And then patients who have cancer of any kind. So if you've got cancer you really should avoid giving the diagnosis idiopathic. And so, the predominant secondary causes that we see here with negative imaging studies are hypercoagulable even see causing venous sinus thrombosis for which you need an MRV, paraneoplastic optic neuropathies that can mimic papilledema, and IIH and the medicines-either side effects of the medicines causing ICP directly or causing disc edema and mimicking that. And so, those cancer patients, especially if they're on immunosuppressive agents, can have optic neuropathies that look like pseudotumor cerebri. So, I personally prefer the term IIH over pseudotumor if you're going to call it anon-idiopathic, you can call it a secondary pseudotumor syndrome or a secondary intracranial hypertension. Beware of the medicines, think about anemia and inflammatory diseases, and cancer.