| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York |
| Transcript |
" Okay, so I want to talk to you a little bit about IIH. You can watch the video on the regular version of IH, what I want to talk to you about is when we would do a bolt intracranial pressure monitoring in IIH, and the two circumstances that we do this in is if we don't have documented increased intracranial pressure on the opening pressure with the lumbar puncture. So as you know, the modified dandy criteria required that we have an elevated ICP documented on the spinal tap but sometimes the patient's pressure come back 20 or 18 and then you're like, well that doesn't technically meet the criteria. In these patients we're going to have to rely on both the radiographic features of increased intracranial pressure, and so on MRI, what we're going to be looking for is fluid in the sheath, flattening of the globe, empty sella and stenosis of the distal transverse sigmoid sinus. So if we have a 20, plus the MRI features of increasing ICP, that's kind of good enough. On the eye exam we're going to be looking for sixth nerve palsy and papillary edema, so if we have evidence of increased intracranial pressure radiographically or clinically, as long as the CSF is normal, we can accept a borderline ICP of 20 to 25. The problem is when you get numbers like 18 and 16, it's hard to use even with these criteria and so that is one of the indications for the voltage cranial pressure monitoring. The other is if they already have a shunt in place; so normally we're just testing the integrity of the shunt with the normal things: shunt series to make sure it's connected, shunt to gram with nuclear medicine, but sometimes we have to do the spinal tap, but even with the spinal tap and the shuntogram and the nuclear medicine, there's some question in some of these patients for which a bolt monitor is necessary to see what the pressure is doing over time. And so when we have intracranial pressure monitoring, we have these waves that correspond with both the arterial phase of the blood pressure as well as the compliance of the brain and the aortic valve closure, so that blood pressure pushes the CSF along and so when we have the systolic, the diastolic, and the in-between thing, the brain compliance, these produce pressure waves that we can measure on intracranial pressure monitoring P1, P2, and P3. It's this P2 one that represents the brain compliance and that's the one we're looking for on the ICP monitor. So as you know when we're doing ICP monitoring we need neurosurgery, they're going to put the bolt in, the bolt can go right into the ventricle with a transducer or we can have epidural - you have to let neurosurgery decide on whether they're going to put the bolt and how far down the bolts going to go. Various different types of these bolt monitors but they're basically direct transducer measurements of the intracranial pressure. So, when we do both ICP measuring in patients who have elevated ICP but we didn't get to see it, the p waves might look like this where the P2 is markedly elevated all of a sudden because we have something wrong with our brain compliance, and that might document that the person whose spinal tap was 18 actually has a pressure of 32. And so sometimes they get really big spikes and even though these are spikes, not plateaus, they're called plateau waves. So the plateau wave is when you have an intermittent, very short lived, rapid elevation in the intracranial pressure and the bolt monitor can record this spike in the pressure. And during these pressure spikes the patient might be markedly symptomatic, they might have a seizure or a transient ischemic event and that cannot be detected on a regular spinal tap. So, normally we just do the regular spinal tap in IIH but sometimes we have to have a direct transducer measurement with a bolt intracranial pressure monitor, the two circumstances are when we have a normal spinal tap or two or three even, or if we have a shunt in place and we are still wondering about the pressure, we're looking at measurements of the pressure that measure the brain compliance and that is the presumed mechanism of increased intracranial pressure on an idiopathic basis, and we might see marked elevations of the intracranial pressure, the so-called plateau waves and all of those would support that even though the ICP was normal in the spinal tap, it really is idiopathic intracranial hypertension." |
