I will ask Dr. Jonathan Pace, please, to come up to the podium to present his paper, Lumbar Puncture Feasibility in the Presence of Cerebral Mass Effect. Good afternoon, everyone. Again, my name is Jonathan Pace, and I'll be talking with you about lumbar puncture feasibility in the presence of cerebral mass effect. So, Quinkie first described the lumbar puncture in 1891, and since then it has become a crucial part in the diagnosis and management of many central nervous system infections and other pathologies. The role of lumbar puncture has been challenged by sporadic reports of fatalities secondary to its performance. And really, the support relies upon individual preference or consensus guidelines. It is now the standard to screen for cerebral mass effect prior to the performance of lumbar puncture in most, if not all, patients. And historically, lumbar puncture was and continues to be effective in many different types of pathologies, including the diagnosis and management of pseudotumor cerebri and the workup of suspected CT-negative subarachnoid hemorrhage. However, the question does remain regarding the safety of lumbar puncture in the presence of space-occupying lesions intercranially. So, Cushing, in 1909, asserted that there are some absolute contraindications to performing lumbar puncture, and eventually, he related this to the presence of papilledema and that this was the finding that really should raise concern prior to performing the lumbar puncture. However, many individuals, Schaller, Lubick, and Murata, and then Corian in 1959 even, have continued to discuss this and say that there may be possibilities that lumbar puncture is safe to perform with diffusely raised intracranial pressure, as well as in the presence of space-occupying lesions. Masserman, in 1933, started out by looking at fresh human cadavers, and he tested the pressures throughout the CSF space in the cisterns, as well as intraventricularly, and noted with the withdrawal of fluid, there was an equal decrease in the pressure seen. Without any space-occupying lesions present, he did not note any herniation events or movements intracranially. Now, he also noted that with artificial creation of a space-occupying lesion by infusing paraffin either into the frontal or occipital lobes, and again, withdrawing volume, the pressure decreased equally between all the compartments, and there was also no herniation events identified. However, when injecting the paraffin into the cerebellar hemisphere, obstructing some of the CSF flow and CSF pathways, this may have caused some herniation events, according to his study. So, what this study is looking at is really trying to identify the elastance and compliance of the system. Here, we see Sklar looking at the pressure-volume curve in nine canines, and this is looking at the elastance of the system, the change in pressure for a given change in volume, and initially, you can see that the change is quite linear up to a certain point, and this is something that we know from our clinical experience as well. At that certain point, the change becomes exponential, that a small change in volume can create a large change in pressure. Now, true brain compliance is difficult to measure. It's the reciprocal of the elastance, and many folks have tried to go about this. Marmoreau looked in felines and created a mathematical model looking at this, which really re-demonstrated these findings. So, we have mathematical models and animal models. What we care about is our patient population, and this is where the lumbar-pneumoencephalonogram can give us an idea about what's happening. We heard about this a little bit from Dr. Benzel when he was doing the air myelograms, but with withdrawal of large amounts of spinal fluid, there can be rapid shifts in the pressure, and even with the overt tonsillar herniation being the main contraindication, the historical accounts describe a mortality anywhere from a quarter percent up to 30 percent concerningly. So, this was looked at further in other studies. Pertinently, Karish looked in children, actually, performing lumbar-pneumoencephalograms and noted two percent fatality, although this was unrelated to the lumbar-pneumoencephalogram itself. It was more due to their systemic disease, and most folks more recently have noted a complication rate from, you know, 0.5 percent up to 1.2 percent. Importantly, the lumbar-pneumoencephalogram has been a diagnostic modality for the diagnosis of intracranial mass lesions prior to the CT era and was a diagnostic modality for downward herniations. So, all this to say in one sentence that CSF pressure is independent of brain shift and that the change in the intracranial pressure as measured by lumbar puncture may not predispose to brain shift necessarily. So, Heidelberg Group looked at lumbar puncture in severe TBI and subarachnoid hemorrhage and noted that if the basal cisterns are patent, this may be safe. This is controversial and as was noted in the editorial that discussed this, just as another perspective. Now, this brings us to our patient population. We looked at all of the patients at our institution who received a lumbar puncture from 2007 to 2018 in a retrospective fashion. Of those patients who received lumbar puncture, we looked at those who received intracranial imaging within a week either before or after the lumbar puncture, and that's who we included in our study. That gave us the 1,000 patients. And of those, we screened their intracranial imaging and saw that 132 had evidence of intracranial mass effect, either with midline shift, different types of herniation, subthalasian herniation, onchal herniation, and then ventricular refacement as well. We saw that all of these patients tolerated the lumbar puncture well, and all but four survived for a week afterwards. The four that didn't survive were severely ill and family had elected to withdraw care. So, the conclusions from this retrospective series is that lumbar puncture may be safe to perform in select patients with intracranial mass effect, and the efforts, again, must persist to regain the confidence in this procedure. Now, moving forward, anatomical findings should drive the decision-making process. Low-volume lumbar punctures we think might be safe in subthalasian herniation, again, the midline shift less than four millimeters, and then partial cisternal refacement but not obliteration, again, to ensure the preservation of the CSF communication throughout the entire CSF space. Additionally, lumbar puncture might be safe in other larger supratentorial space-occupying lesions, as well as in specific posterior fossa involvement, such as one of the patient populations that were excluded was a perioperative patient population where these patients received a lumbar drain prior to posterior fossa surgery for acoustic neuroma surgery, for instance, for CSF diversion. Even aside from the surgery itself, this may be a safe population, although we did not specifically look at them. Clearly, there are limitations to this study. It's retrospective in nature, and there are other further limitations regarding space-occupying lesions in the heterogeneous population that we studied. However, going forward, building a prospective consortium may be important so that more patients can benefit from the diagnostic and therapeutic lumbar puncture. So far, 19 centers across the globe have agreed to participate in this prospective consortium, including seven from India, Taiwan, multiple across North America. If there's any interest in this, there's a website and then our e-mails on the next slide that you can contact us with the aims of really establishing the safety of this procedure going forward. I'd like to acknowledge the co-investigators and department at University Hospitals. Thank you. Questions from the audience, please. I submit that your study simply shows that practitioners in Cleveland have been able to select patients for whom lumbar puncture is safe over the years successfully. You don't know what patients didn't get lumbar punctures because their clinicians were intimidated by their CT scans. That's true. I agree. I think that's why, at least going forward, limiting it to what we saw has been safe in the past would be the appropriate place to start, but I agree. Thank you. However, you could look at the patients that had a CT scan after the lumbar puncture, right? This would be the subsection because it was not known beforehand. That's true. Thank you. Very good.

lumbar puncture

cerebral mass effect

central nervous system infections

CSF pressure

intracranial mass effect