Melanie Cole, MS (Host): Welcome to UAB MedCast. I'm Melanie Cole, and we have a panel for you today with two UAB Medicine physicians. Joining me is Dr. Will Meador. He's a Neurologist and an Associate Professor. And Dr. Jesse Jones, he's an Interventional Neuroradiologist and an Assistant Professor, and they're here to highlight spontaneous intracranial hypotension for us today.

 Doctors, thank you so much for joining us. Dr. Meador, I'd like to start with you. Please tell other providers that may not have heard of this not very common condition; what is spontaneous intracranial hypotension? The prevalence? What's the scope of what we're talking about here today?

Will Meador, MD: So, spontaneous intracranial hypotension refers to patients who have suffered from headaches typically associated with reduced pressure around the brain causing tension on the dura which leads to headaches. And typically, about 92 percent of these patients will have an orthostatic headache as their presenting symptom, whereby, when they stand up, they have headache that resolves with laying down, typically within about 15 to 30 minutes of laying down. But it is worth noting that in these patients, about 5 percent of them have a non-orthostatic headache, so it needs to be considered in other forms of headache, and about 3 percent have no headache at all.

Host: Dr. Jones, do we know why this happens?

Jesse Jones, MD: The leaks can be from a number of different causes. And that's part of the workup is identifying where the dura has been torn to allow the cerebrospinal fluid to leak out and result in a spontaneous intracranial hypotension or SIH. There's three known mechanisms, which I'd say are the most common. In addition to that, there's some less common ones. But typically the dura can be weakened around the nerve root sleeve of the spine, typically the thoracic spine forming a meningeal diverticulum. And that diverticulum is very weak and it can weep out cerebral spinal fluid. Secondly, if the patient has any kind of degenerative disease of the spine like arthritis they can develop little bony outgrowths or calcifications that will eventually kind of wear away or indent the dura and cause a leak typically ventrally along the thoracic spine.

And finally, there's a more recently understood entity called a CSF venous fistula, in which the cerebrospinal fluid as it's normally filtered into the blood through a regulated pathway; that pathway is somehow injured or destroyed and the cerebrospinal fluid kind of just rapidly fistulizes with the vein and drains out through the vein. And that's also most commonly in the thoracic spine.

Host: Dr. Meador, speak a little bit about diagnostic criteria as a patient would come to you or present in the emergency room. When are you seeing them? And what's the diagnostic criteria? How do we know this is what's going on?

Will Meador, MD: So the patients can present in several different ways. It has been reported that a sudden onset severe headache, kind of often mimicking the thunderclap headache often associated with subarachnoid hemorrhage, can be a form of presentation of this headache. So it can present through the emergency room, but typically these are chronic headache patients who've had headaches for weeks, if not months that are really, quite problematic.

In fact, there was a recent study that came out in March looking at the quality of life of these individuals suffering from SIH. And they had a surprisingly low quality of life rating below that of patients with multiple sclerosis or similar to that of patients with cancer. So it's a very disabling headache and they may present after weeks or months of a lot of misery.

As far as getting to the diagnosis, typically a headache that is orthostatic in nature would then prompt routine imaging such as an MR of the brain to look for evidence of SIH. And I'll let Dr. Jones go into detail of what we look for on that imaging as we're working these patients up, but I would note that about 20 percent of the patients, up to 24 percent, will have normal routine imaging.

Jesse Jones, MD: Yeah, so Dr. Meador, I think the MRI brain can be useful, especially in that population you mentioned, who are not necessarily orthostatic. The classic findings of intracranial hypotension are what you alluded to, just the sagging of the brain. And typically, that can be quantified by measuring some angles relative to the clivus, which is a bone in the interior portion of the brainstem measuring the amount of sag. You can also see this as the cerebellar tonsils herniate down below the foramen magnum, and that can also be measured.

And as you mentioned, routine imaging typically does not include IV contrast. If you do get a study with contrast; what you'll often see is enhancement of the dura, and what's happening there with the so called pachymeningeal, or diffused dural enhancement. There's two layers of dura, and those layers spread apart with SIH because the pressure is so low.

They're not kind of squished together anymore, and so you see a thick kind of rind of enhancement between those dural layers, which is a pretty classic finding. In more severe or prolonged cases, you'll start to see evidence of some brain damage. You can see chronic subdural hematomas form as that low pressure allows blood to collect under the dura, and a phenomenon called superficial siderosis, which is a fine or thin kind of sugar coating of chronic blood products over the brain, typically in the posterior fossa or around the cranial nerves. And this can actually manifest as hearing loss. It primarily involves the acoustic nerves.

Will Meador, MD: And getting, to the acoustic nerve involvement and cranial neuropathies that Dr. Jones mentioned, a lot of these patients will have other symptoms in addition to headaches, such as dizziness or vertigo. They may have hypoacusis because of stretching and involvement of those cranial nerves. Tinnitus and nausea are common, and many of these symptoms actually can overlap with the symptoms of Chiari or of POTS, which is postural orthostatic tachycardia syndrome.

Jesse Jones, MD: Dr. Meador, what's your feeling about lumbar puncture in these cases in terms of measuring? Is that kind of no longer an established criteria or do you think that still has some validity? .

Will Meador, MD: It's a great question. Historically, it was thought, well, if we think this is hypotension, let's prove it, right? And get a spinal tap. But unfortunately, only about a third of patients with SIH actually meet the criteria of having less than three centimeters water of pressure in their CSF. So it's really not that helpful.

And it actually can make it worse because of course, we're introducing trauma to the dura which can lead to further leakage of spinal fluid, which can worsen the headache. So it's really not advised to do that in workup of these individuals.

Host: Dr. Jones, I'd like you to speak about treatments and how the treatment approach varies based on the severity of the condition. Because as Dr. Meador said, this is so quality of life limiting and sometimes more than many other conditions. So speak a little bit about how shared decision making and treatment modalities go together.

Jesse Jones, MD: Well, I think if we're talking about a patient who has presented with say an orthostatic headache and they've got some imaging to verify or to support the fact that they do indeed have SIH, such as some of the MR findings of the brain that Dr. Meador and I just recently described; at that point, if I'm referred a patients such as that, what I'll typically start with is an epidural blood patch, and that's a procedure where we take some of the patient's own blood from IV, and we inject it back into the space just superficial or surrounding their dura, and what that blood will do is it forms kind of a gelatinous like material, and it will seal around the dura over a long segment far from where it's initially introduced, which is typically somewhere in the lumbar spine or occasionally two sites are chosen, one in the thoracic spine and one in the lumbar to get a little larger of a coverage area.

But what that blood will do is it will diffuse out and kind of coat the dura temporarily and hopefully give some time for that dural tear to heal up.

Will Meador, MD: And this is really a standard of care if SIH is strongly considered because the downsides to epidural blood patches are quite low. But the benefit can be tremendous. So about 64 percent of patients with SIH do derive benefit from an epidural blood patch. So it's actually quite effective, but you do want to make sure that you're using large volumes of blood up to 40 milliliters of blood for the epidural blood patch.

And then you want to instruct the patients to be recumbent for about two hours after the procedure and really try to avoid any strenuous activities for six weeks following it. And that can actually be quite effective for most individuals in this situation.

Jesse Jones, MD: Yeah, just to echo Dr. Meador, I think the blood patch is surprisingly efficacious and perhaps more importantly, it can be diagnostic with patients who were a bit struggling with the cause of their headaches and may have a complex presentation. A patient who responds to a blood patch, even temporarily in my mind, actually strengthens the presumptive diagnosis.

Host: Dr. Meador, can you speak about management of SIH with other providers and collaboration in a multidisciplinary way? Because you mentioned bed rest and the patch, and so who else is involved in management of these patients?

Will Meador, MD: So it typically starts with you know, what we refer to as conservative treatment, which is non-interventional treatment. And that can be trying to be recumbent as much as possible during the day, even limited to bed rest. Caffeine intake can actually help with this type of headache by causing vasoconstriction in the dural blood vessels.

And of course, serious hydration, right? So I tell these patients to drink as much water as they can tolerate because we don't want to limit their body's ability to make spinal fluid to replace what is being lost. And up to 28 percent will have spontaneous resolution with that. So that's the first place to start.

But I think quickly getting over to the epidural blood patch and as a neurologist, I'm not trained to administer those. Typically our anesthesia team does those at our facility. So we will reach out to the anesthesia team, explain the situation, and they are usually able to get those patients in pretty quickly for epidural blood patch.

And that really, again, should be considered very early on. It has been shown that the longer we wait to try the epidural blood patch, the less likely it is to be efficacious. So I think doing that early, if you strongly consider SIH, is important. Of course, if you can find a leak and there are advanced imaging techniques which can be used to do that that Dr. Jones can outline. Then surgical options would be next.

Jesse Jones, MD: Yeah, so I think in addition to what Dr. Meador mentioned about the initial management strategies, there's a subset of patients who just either don't respond to conservative measures or they may undergo a blood patch and receive relief for, say, several days or even a few weeks, but the headache comes back, and in those situations, we tend to move on to trying to identify the source of the leak, and they can actually be quite hard to find.

It takes someone who's skilled in the art of myelography, which is the injection of contrast material into the thecal sac and really closely evaluating the images that are obtained following myelography to find these leaks. And that's something that we do at UAB quite regularly. That can be done with a combination of CT scanning, and we've actually got a state of the art neuro CT scanner, which is has protocols on it for identifying leaks, which has been very helpful for us.

That's called a photon counting detector. And there's also, for those CSF venous fistula I mentioned initially, that requires a special kind of myelogram called the digital subtraction myelogram, where a patient will hold their breath for typically around 20 to 40 seconds. And during that time, we'll inject dye into their thecal sac and image typically, about once a second over that 40 to 60 seconds and actually watch like in a movie as that contrast moves through their thecal sac looking for any place that may be leaking out.

Host: This is such an interesting discussion today. Doctors, I'd like to give you each a final thought here. Dr. Meador, what would you like other providers to take away from the criteria that we have discussed today for SIH?

Will Meador, MD: I think having a low threshold to consider SIH in a patient with daily headaches where it may be unclear because especially later in the disease course, these individuals may lose that orthostatic nature of the headache. And so if you have an unexplained daily headache, think about SIH, get the MR of the brain with gadolinium to investigate and then consider referral for a blood patch if there's any findings supportive of it.

Host: Dr. Jones?

Jesse Jones, MD: Yeah, I agree. I think working these patients up early before they become chronic and when the disease becomes perhaps less obvious or less intuitive to diagnose is extremely important. With patients who don't respond to typical measures such as conservative therapy, a referral center such as UAB with more advanced imaging capabilities and also treatment is a great idea.

Host: Thank you both so much for joining us today. And for more information, please visit our website at uabmedicine.org/physician. That concludes today's episode of UAB MedCast. I'm Melanie Cole. Thanks so much for joining us today.