| Transcript |
Today we're going to be talking about pseudo-papilledema. Pseudo means false, so pseudo-papilledema means it looks like the disk is swollen, but it's not swollen. And so, what could make the disc look swollen, but it isn't swollen? So, before you can decide if something is pseudo, you kind of have to know what makes it real edema. So, in patients who have real papilledema, that term we generally reserve for increased intracranial pressure. Any other cause of optic disc edema we just call that optic disc edema, but if you know that it's from increased intracranial pressure, we call that type papilledema. And in papilledema, the patients normally have symptoms of increased intracranial pressure. And the symptoms of increased intracranial pressure are headache, double vision from a non-localizing sixth-nerve palsy, transient visual obscurations lasting seconds at a time, and they may have pulse-synchronous tinnitus, nausea, and vomiting. Those are the major symptoms of increased intracranial pressure. Any time you have any other symptoms, then you have to find some other cause for that. These are the symptoms of ICP. And, the distinctive signs of increased intracranial pressure, in addition to papilledema, are the visual field might show an enlarged blind spot because the optic nerve is the blind spot. If the blind spot is bigger, that's from swelling of the disc, papilledema, or any type of nerve fiber layer defect is a papilledema visual field. And you can have a sixth-nerve palsy as a non-localizing finding of increased intracranial pressure. Any other finding would probably mean you have to find another reason for them to have it. You cannot blame the ICP for a seventh or a hemiparesis. There has to be some other cause. And then we're going to be looking for the radiographic signs of increased intracranial pressure.And the MRI scan is better than the CAT scan for looking for these radiographic signs and also,it's better for excluding the causes of papilledema. In general, we would recommend an MRI of the head, the orbit, and an MR-venogram to look for venous sinus thrombosis in every patient with papilledema. The radiographic signs of increased intracranial pressure are fluid in the sheath, flattening of the globe, empty sella, narrowing of the transverse sinus at the transverse sigmoid junction.Any other finding that you have radiographically cannot be really attributed to increased ICP. And then we're going to do the lumbar puncture, of course. And if idiopathic intracranial hypertension, the CSF better be normal. And in other causes of increased intracranial pressure, the CSF might show meningitis or red cells from subarachnoid hemorrhage, but in IIH, the idiopathic form of intracranial hypertension, we want the CSF to be normal and we have to document an elevated intracranial pressure on the opening pressure on the spinal tap. The reason that's important is that's kind of the first step in determining whether someone has pseudo-papilledema, not looking at their optic nerve. That's the last. We have to think about these other things first. So, the first thing we're going to do in a pseudo-papilledema patient is see if there are any symptoms of intracranial pressure. So, they really shouldn't have headache or double vision. Now what they can have though is the transient visual obscurations lasting seconds at a time. So, both pseudo and true papilledema can have the transient visual obscurations. The signs of increased intracranial pressure, so we don't want to see a sixth or we don't want to see any of the distinctive features of increased intracranial pressure from papilledema. And those pathologic features are hemorrhage, exudate, subretinal fluid. If we see any of those features, those are not really features of pseudo-papilledema. So those are what we would call obligatory signs of increased intracranial pressure. So, the obligatory signs would be hemorrhage, exudate, cotton wall spot, subretinal fluid. Those things do not occur in the pseudo-papilledema patient. And we might be looking for the radiographic findings of increased intracranial pressure if the patient has already had an MRI. However, a CT scan might show that there's calcium in the disc and that calcium is one of the markers of pseudo-papilledema because the most common cause of pseudo-papilledema is optic disc drusen. Ultrasound also might show either drusen, calcified drusen, Hyperechoic signal on ultrasound versus fluid in the sheath, especially when we do the 30-degree test, that's a sign of increased ICP. So, these imaging things can help differentiate pseudo from real papilledema. And if you need to, you could do a spinal tap but normally you can just tell by looking. So, in the absence of the obligatory signs of true papilledema, we're going to be looking for drusen. If we see the drusen, then we don't to keep doing anything for that person. And the main thing that we're looking for is in the Frisén scale, which is the most commonly used scale for papilledema, elevation of the peripapillary nerve fiber. So, in the Frisén scale in grade one papilledema, we're going to see elevation of the disc in a nasal-crescentic pattern like this. And over time, the Frisén scale shows increasing obscuration of the nerve fiber layer. And that obscuration of the nerve fiber layer blocks the blood vessel as it crosses the margin. And so, in a Frisén grade one, we have a ring, a crescent of elevation nasally. In a two, the ring goes all the way around, 360 degrees. And in a three, we have the distinctive sign, which is obscuration of the blood vessel as it passes over the margin. So, when we're looking at true disc edema, we want to look right here at the margin of the disc to see if the blood vessel is obscured. If the blood, the blood vessel is obscured, it tells they have true obscuration of the peripapillary nerve fiber layer from true edema. In pseudo-papilledema like drusen, the obscuration is under the blood vessel. In true edema, the nerve fiber layer is on top of the blood vessel. So, if we lose the blood vessel here, that's a three. If we lose it here in the center, that's a four. So, a three and a four are kind of what we're looking for to differentiate true papilledema based on obscuration of the nerve fiber layer. A two and a one are a little bit harder. And so, a two and a one probably need to have both symptoms, signs, and the radiograph to help us differentiate. And by radiograph, I usually mean ultrasound for drusen and fundus fluorescein angiography because true disc edema will cause leakage of the fluorescein from breakdown of the blood-optic nerve barrier versus pseudo-papilledema will just stain. And it turns out that fluorescein probably is better, but ultrasound is good if it's positive. If it's negative, we're going to need fluorescein. And if you need to, we'll go to the MRI, looking for the radiographic findings. And then if, ultimately, you might still have to do a lumbar puncture. So, in general, pseudo-papilledema is defined by looking for symptoms, the obligatory signs, and using the imaging to help us confirm that we have true or pseudo-papilledema. The most common cause is drusen. If it's calcified drusen that's easy. If it's non-calcified drusen, you might have to use fluorescein. And some of the cases we still have to do a lumbar puncture on. Look at the Frisén scale, and if we see a three or a four or a 360-degree of elevation with any obligatory sign, those are easy. The hardest one is grade one or grade one-half to grade one. True papilledema can look exactly like pseudo-papilledema even to trained experts, and for that, I would go back to the imaging studies that we have. And, one day, OCT will be able to tell us this. OCT can see the nerve fiber layer, it can see the thickening, and with enhanced depth OCT we can see the actual drusen. I'm not sure if OCT is good enough to make the diagnosis yet, but we're using it more and more. So, in summary, you should really consider the whole picture, not just looking at the disc itself, in determining whether someone has pseudo or true papilledema. |
