Dr. Aruna Rao at the 2023 Cedars-Sinai Intracranial Hypotension Conference
Dr. Aruna Rao, assistant professor of neurology at The Johns Hopkins University School of Medicine, presented this talk titled “CSF Dynamics: Intracerebral Pressure Monitoring in CSF Hypotension” at the 2023 Cedars-Sinai Intracranial Hypotension Conference on July 8, 2023. The conference was hosted by Cedars-Sinai with generous support from the Spinal CSF Leak Foundation in Kohala Coast, Hawaii.
Transcript
[00:00:12] Hello, everyone. I’m going to be talking about intracerebral pressure monitoring in the diagnosis of cerebrospinal fluid hypotension. I have no disclosures. So, thus far, literature has given us a lot of information about the role of monitoring for non-traumatic settings, primarily traumatic settings but in the non-traumatic domain, there’s been very little data to draw any reasonable conclusions. In non-TBI settings, typically it was strokes or subarachnoid hemorrhages that the data was obtained that showed, um, ICP for above 20 millimeters of mercury for more than five minutes is associated with an unfavorable outcome.
[00:00:51] And these are the numbers that we use today in the ICUs. ICP monitoring, though, has been proposed for ischemic injuries, et cetera. But thus far, there has not been any data. So in our center, we use ICP monitoring and evaluating patients who present with symptomatology suspicious for a CSF pressure related diagnosis where the exam or imaging findings and lumbar punctures are inconclusive.
[00:01:19] And the objective of this study was to look at the utility of elective intracerebral pressure monitoring and the diagnosis of patients being evaluated specifically for cerebrospinal fluid hypotension disorders, and to determine the correlation between imaging markers, the Bern score, particularly, in patients who have confirmed CSF leaks and also to determine outcomes of diagnostic testing and interventions.
[00:01:43] I mean, it is a small study. It’s still a pilot study. We have so much more data to analyze. So keep that in mind when we look at the data. So it is retrospective. We have thus far analyzed 80 patients. Unfortunately, most of, and I shouldn’t say unfortunately, but most of our patients are shunted patients, where we do make a lot of shunt adjustments and changes based on their ICP monitoring data.
[00:02:09] And out of the 80 patients that we’ve analyzed so far, only 25 patients were non-shunted, which are the ones that we chose for this study. And these patients presented with CSF hypotension symptoms based on their clinical presentation, their imaging findings, particularly their Bern score and myelogram positive results.
[00:02:28] So our ICP monitoring is done with a Codman Integra piezoelectric intraparenchymal monitor and we leave it in for about 24 to 72 hours, sometimes longer if we need to make shunt adjustments, etc. It’s connected via an A2D converter and the data is recorded via lab chart software, which we export for analysis.
[00:02:47] In addition to interstitial pressures, we also obtain cardiac monitoring, respiratory monitoring via a pulse oximetry and finger plethysmography. Heart rate and blood pressure are taken manually, particularly during the positional testing, as I’ll show you later. So this is the Codman Integra monitor that we use.
[00:03:06] And this is the output that we get. And this is in a normal patient physiologic ICP with both cardiac and respiratory modulation. I’m particularly interested in respiratory modulation because of my other life in sleep medicine. And we do see quite a lot of changes in patients with sleep apnea and sleep disorder breathing.
[00:03:24] So the way we collect our data, so overnight, we get continuous ICP recordings with patients in the supine position, 8 to 12 hours, and they’re analyzed in 60 second bins. Overnight continuous pulse oximetry, as I mentioned, finger plethysmography and electrocardiography is obtained as well. During the day, after having the patient sitting up for several hours, we’ll do positional testing with the head of bed at several degrees.
[00:03:50] So starting with supine, 10, 20, 30, 45, 60, because that’s how the beds are made—they go to 30 to 45 and then 60 degrees —each position for five minutes. And we collect the data at the end of that five minutes. Sitting, standing ICPs are obtained for a little bit longer time, 15 to 30 minutes and walking typically about 2000 steps.
[00:04:13] We also do other testing. We’ll have the patient valsalva, we’ll have the patient bend forward. Whatever brings on their symptoms, I have them do at the bedside. I also have patients running up and down the stairs, and we look at their ICPs later, we walk them much longer if they look like they’re slow leakers.
[00:04:31] So it can get very creative with this. I’ve had people say, Oh, I lift up my heavy dog. And so we’ll find like beanbags or whatever for them to lift up or sandbags, to try to mimic what they come in with with their complaints.
[00:04:43] So all the values we report as minimum, maximum, and average in all the positions. Of course, we got the demographic and clinical information from chart review, and the Bern score was calculated by two independent neuroradiologists for each patient. So, this is in a patient with no CSF leak but as you can see here the ICP is lower, and it can be anywhere from positive five to negative 10, which are our cutoffs.
[00:05:12] Actually positive 20 for the high number and negative 10 for the low number, but it could really vary in the sitting position, even for normal patients. Um, this is a patient with multiple perineural diverticula. And as you can see here, the numbers are much lower, negative 10 and below. And I’ll show you more.
[00:05:31] This is a patient where there is an orthostatic drop in the ICP in the standing position. In this patient with a CSF venous fistula, again ICP while sitting was in the negative 14 to negative 16, 17 range. Both of these last two patients had normal opening pressures, lumbar punctures. So looking at our data, and our group of patients they were pretty well matched.
[00:06:01] Again, small sample size. Age-wise, pretty similar. More women, as expected, lower BMI in the CSF leak group. We looked at their medical comorbidities, nothing to make out of this here, but all 100 percent of the ones with leak presented with headache as well. Only 84 percent of patients without a leak presented with headache and 91 percent of patients with a leak had a positional headache significant with their symptoms and high rates of migraine headaches as well, as we’ve heard in other talks that the headache can be quite non-specific. And we have here that 75 percent of patients were referred for low ICP did end up having a confirmed leak, so our pre-test diagnostic tools are effective.
[00:06:52] So this is just data looking at the pre-evaluation opening pressure. And again, as other people have shown, it was not significantly less in patients with CSF leak compared to those without, and just indicating that opening pressure is not always a useful marker for CSF hypotension. We did find— this was a little surprising to me— we found the lowest nighttime ICP may be predictive of a CSF leak. So patients with a CSF leak here are shown in the red, and the patients with no leak shown in the black, had much lower pressures. Normally, when I look at these numbers, overnight numbers, we’re looking for the high numbers because we’re looking, we’re looking to identify patients with IIH with the high supine overnight numbers, but normally, I don’t look at the minimum too closely.
[00:07:43] But, you know, after this data, I feel like this is going to be something that I’m going to pay closer attention to. I mean, we collect it; I just didn’t realize the significance. So here again, the minimum ICPs, we looked at a different head of bed positions. And this was also surprising, on the y axis we have the ICP and on the x axis we have the head of bed position. Again the black is patients with no leak and the red is patients with a leak. And we found that patients in the 10 degree angle particularly had lower ICPs. 10 and 20 degrees had lower ICPs than the other head of bed positions. The only explanation I can think of for this is that auto regulation kicks in probably after 20 degrees, and we’ll see further also stops working at standing.
[00:08:39] So that was the minimum ICP. We also looked at the average ICP with different head of bed positions in CSF leak patients. And again, once again, the 10 and 20 degrees, but in this case, particularly the 20 degree position had patients had lower pressures. Again, no statistical significance because of the small sample size, but certainly looked like there was a trend.
[00:09:04] So we’ve heard so much about the Bern criteria. Dr. Parker, I think, did my work for me with this. And so we use this to look at our imaging. The only caveat to this data here is that some of the imaging wasn’t at the time of the monitoring. It may have been days before, weeks before, and even months before.
[00:09:25] I think the latest we saw was six months before. So that might explain some of our data. So, this is just the Bern score pachymeningeal enhancement, venous engorgement, etc. And in our group, some of the studies I looked at said that the major criteria were more significant in patients with CSF leak.
[00:09:44] However, in our group, the supracellar effacement, prepontine effacement, and mammalopontine effacement were much more significant. So that’s something that we’re going to have to look at more closely to see if there’s a difference in the different components of the score. I’m very curious from all the data we’ve heard today to follow some of the speaker’s data.
[00:10:07] So the Bern score is a good metric that we could, that we use. It did not, however, so, um, if you recall, the minimum ICP overnight was lower in patients with CSF leak. However, the Bern score did not correlate with the minimum or maximum ICPs.
[00:10:25] So, we looked at the Bern score. Also, the above, um, three here are sitting, standing, and walking ICPs in patients without a leak, and the below three are Bern score in the sitting, standing, and walking positions in patients with a leak. And the patients’ standing minimum ICPs did correlate with diagnosis of a CSF leak.
[00:10:56] So, this is our treatment algorithm. I have to give credit to Dr. Majid Khan. I borrowed the information for this slide from him. He’s our interventional radiologist. So the way the workflow goes is, suspected intracranial hypotension patients then get an MRI with contrast, spine imaging without contrast, a fat-sat imaging.
[00:11:17] And if they’re positive for brain imaging and spinal collection then they get the dynamic CT myelogram, or DSM with patient in the prone position, and they get a targeted patch. If the brain imaging is positive, but there’s no spinal collection identified, then they get the dynamic CT, a myelogram or DSM in the decubitus position, and a non-targeted patch if there’s no leak seen.
[00:11:43] So thus far for our patients, of the 25 patients, 12 of them had positive myelograms, 11 had targeted fibrin glue patches, and one, not sure why, is being worked up for a skull-base leak at the moment. One of our patients that had the fibrin glue patch did develop rebound hypertension and required a shunt.
[00:12:02] Two had repeated blood patches. One, sadly, on the way home after her admission, like coughed or sneezed and had to come right back. And among the patients that were myelogram negative, only one had a non-targeted patch and most of them were referred to our headache colleagues. However, our headache colleagues are very well versed in CSF disorders and many of the patients get referred back to us, and four had repeat myelograms, which were positive. One CSF venous fistula and one skull base leak were identified.
[00:12:39] So to conclude, in intercerebral pressure monitoring, using that as a tool in patients with CSF leaks, the lower minimum nighttime ICPs were more significant. There’s a possible trend toward lower minimum ICPs at 10 and 20 degree head position and a lower average ICP in supine 10 and 20 degree head positions as well in patients with CSF leak. Higher Bern score in patients with CSF leak inversely correlates with the minimum standing ICPs in patients with CSF leak. So of course, we have limitations because of our sample size. However, the trends seem to be quite promising. And as I mentioned before, the time from between the ICP monitoring and neuro access imaging was variable, um, sometimes in the order of months.
[00:13:29] So, uh, I’d like to thank Dr. Moghekar, uh, and Dr. Solomon, who’s no longer with us, sadly, who taught me everything that I know about cerebrospinal fluid disorders. I’d like to credit Dr. Solomon for some of the slides, the ICP monitoring slides, and, you know, as many of you have shown, this cannot be done without a team.