Rania Habib, MD, DDS (Host): The Hydrocephalus Association estimates that 700,000 adults are living with normal pressure hydrocephalus in the US, but less than 20 percent of them are properly diagnosed, and it is often misdiagnosed as Alzheimer's or Parkinson's. Welcome to MDCAST by Tampa General Hospital, a go to listening location for specialized physician to physician content and a valuable learning tool for world class healthcare.

I'm your host, Dr. Rania Habib. Joining me today is Dr. Naomi Abel, Assistant Professor and the Director of Normal Pressure Hydrocephalus Clinic at the University of South Florida, and Dr. Kunal Vakharia, an Assistant Professor of Neurosurgery at the University of South Florida. They are here to discuss the symptoms, diagnosis, and treatment options for idiopathic normal pressure hydrocephalus.

Welcome to the show, Dr. Abel and Dr. Vakharia. It is so wonderful to have you today.

Naomi Abel, MD: Thank you so much. Glad to be here.

Kunal Vakharia, MD: Thanks so much for having us on today.

Host: We are very excited about this panel discussion, so we'll jump right in. How is adult hydrocephalus defined?

Naomi Abel, MD: Adult hydrocephalus is defined as an active enlargement of the cerebral ventricles, differentiating it from ex vacuo or atrophy, which happens to all of us as a normal process of aging. So adult hydrocephalus has to be an active process.

How

Host: is chronic adult hydrocephalus in adults, abbreviated CHIA, classified? And where does wobbly, wacky, and wet fit I'm sure we can all remember that mnemonic from way back in med school.

Naomi Abel, MD: Yes, that's right. Most of us remember that from med school, but chronic adult hydrocephalus is much more than wobbly, wacky, and wet. That refers to gait disturbance, dementia, and urinary urgency or incontinence, which was first described by Dr. Solomon Hakim in 1965 and is referred to as idiopathic normal pressure hydrocephalus, now proposed to be called Hakim's disease.

But there are other forms of adult hydrocephalus. Transitional hydrocephalus is defined as hydrocephalus, which is diagnosed before the age of 18. Patients are treated with either an ETV or a shunt and then age out of the pediatric system and are now adults.

Then there is acquired or secondary hydrocephalus, which has a known cause such as meningitis or a subarachnoid bleed, trauma. Then the third category is compensated, and compensated includes not only the idiopathic normal pressure hydrocephalus, but also congenital hydrocephalus, in which patients have hydrocephalus before the age of 18, but it does not manifest until adulthood. That is divided into early and late adulthood diagnoses.

Host: And how are those diagnoses of the congenital hydrocephalus, how are they missed?

Naomi Abel, MD: They're not necessarily missed but the patients are asymptomatic, and even though they may have had hydrocephalus all their lives, they've compensated for that until they reach a certain point. We don't know all of the pathophysiology behind why patients at some point become symptomatic, but in early midlife, patients may present with high pressure symptoms such as headaches, nausea, visual symptoms, and when patients present with the same condition in later adult life, they present with symptoms more like idiopathic NPH, the gait disturbance, the bladder urgency, incontinence, and cognitive decline.

Host: Okay. So it's more just they're asymptomatic early on and it manifests later in life.

Naomi Abel, MD: Correct. Then you get imaging, the imaging is differentiated from idiopathic NPH by the ventricles, the size of the ventricles, measurements, and other radiographic features of the brain imaging.

Host: Now, we wanted to focus a little bit more on idiopathic normal pressure hydrocephalus. Why is there a resurgence of interest in VPS specifically for INPH?

Naomi Abel, MD: It's the combination of an aging population and technical advances, specifically programmable valves. The availability of programmable valves have decreased the complication rates very significantly. Only a few years ago, the complication rate was up to 30%. Now it's much lower, closer to 10 percent, and the complications at the 10 percent frequency are less severe. So, it's the combination of the two.

Host: No, that's fantastic. I mean, a complication rate of less than 10 percent is wonderful in any surgery, so that's great. What is the prevalence of INPH, also known as Hakim's disease?

Naomi Abel, MD: Well, the estimated prevalence ranges between 300 to 700,000 in the United States.

Host: We hear a lot about overlap with other neurodegenerative diseases, specifically, misdiagnoses with Alzheimer's or Parkinson's. What do you recommend to ensure proper diagnosis?

Naomi Abel, MD: Those diseases are more common than idiopathic NPH, and the challenge is differentiating them from idiopathic NPH. So,a very detailed history and physical exam, as well as correlation with brain imaging and then putting the constellation of symptoms together with the abnormal imaging, a lumbar puncture or a high volume lumbar puncture sometimes known as the Miller-Fisher test with very detailed gait and balance testing before and after, is helpful to predict which patients will get better with shunting.

Host: Now, what are the primary clinical and imaging features that are supportive of congenital versus idiopathic NPH?

Naomi Abel, MD: So in congenital hydrocephalus, clinically patients may present either early adulthood or late adulthood. The early adulthood presents with headaches, visual problems, and the late adulthood presents with symptoms closer to NPH, the gait disturbance, bladder, and cognitive decline. The Evans Index, which is a radiographic feature, is much greater in congenital hydrocephalus, usually greater than 0.4 as opposed to 0.3. In addition, many patients who have congenital also have aqueductal stenosis or a partial aqueductal stenosis. So there is a tri ventriculomegaly with the congenital patients.

Host: Okay. And for our listeners who aren't as aware of the imaging that is actually obtained to differentiate between these two, are we specifically speaking about radiographic features on CT scans or MRIs?

Naomi Abel, MD: Either. Either. More more features are discernible on MRI, but we can use either.

Host: Okay. And could you describe a little bit more of what that Evans scale is for our listeners who may not be familiar with that scale?

Naomi Abel, MD: Yes, so the Evans Index is a ratio of the diameter of the frontal horns to the skull, to the maximum width of the skull. So it's simply a ratio.

Host: Okay. And what should that ratio be that would sort of push them towards a diagnosis of either congenital versus idiopathic or are they the same for normal pressure hydrocephalus?

Naomi Abel, MD: So, with normal pressure hydrocephalus, the ratio is 0.3 or greater, but that does not differentiate between normal pressure hydrocephalus and ex vacuo, because those conditions can both have 0.3 or greater. Congenital usually has a larger Evans Index, closer to 0.4 or greater.

Host: Okay. Thank you for that clarification. What tests are utilized to determine whether a patient is a candidate for treatment and what treatment options are available?

Naomi Abel, MD: So, the tests are generally the high volume lumbar puncture or extended lumbar drainage, either one. Here at USF, we prefer the high volume lumbar puncture. The treatment is a shunt, whether it's a ventriculoperitoneal, a ventriculoatrial, ventriculopleural shunt, or, in the case of aqueductal stenosis, patients may be a candidate for endoscopic third ventriculostomy, or ETV.

Host: Okay. And how do you as the surgeon make the determination for which patient might undergo one of those options?

Kunal Vakharia, MD: Yeah, so that's actually, the question there is really based on the anatomy that we see on the MRIs. Part of it, especially for an endoscopic third ventriculostomy, is dependent on the location of critical arteries and the cisterns and our approach to opening up an area that allows for a new CSF drainage pathway.

So what we actually do is we put an endoscope in through the brain and create a new pathway for flow whenever we have an obstruction of our normal flow.

That's not always the case, though, and sometimes it's not obstruction that's the issue. And in those situations, sometimes a ventriculoperitoneal shunt is really your only best option.

And so looking at those anatomical features really helps us distinguish the best surgical option.

Host: And what are typically the surgical outcomes for idiopathic NPH? I'd love to hear a little bit more about the risks, the benefits, and just overall outcomes for their quality of life.

Kunal Vakharia, MD: Yeah, so like Dr. Abel mentioned earlier, we have a lot of advancements and granted in the grand scheme of hydrocephalus, there aren't dramatic changes in how we get CSF out of the head into another sterile compartment. But there have been a significant number of advancements in how we are able to program shunt valves and really it gives us a lot more control in how much fluid we drain and at what level we drain it. So historically, we usually say that patients usually have a 24 to 96 percent improvement, but that's largely because there was such variability in the patients we picked, understanding the disease process, understanding how it related to anatomy.

And also understanding how a shunt valve actually played a role in this situation. Nowadays, I think we have a much higher rate of favorable outcomes because our patient selection and our anatomical understanding of what we see on imaging is so much better.

The other thing is like you said earlier, the wet, wacky, wobbly. We have to kind of temper expectations, make sure everyone understands what is the most likely thing to improve, versus the least likely thing to improve and kind of expect that there's going to be a spectrum of results from that.

Host: So specifically, when we talk about those three symptoms, how often do, does surgery actually improve specifically the gait disturbances, the memory loss and the incontinence?

Kunal Vakharia, MD: I think probably in the last decade or so we've seen an increase in how many patients improve from it largely because of patient selection and largely because of those tests and evaluations that we do after large lumbar punctures and large CSF drainage trials. Typically for gait abnormality, that's the one that we see the most dramatic improvement.

Motor function gait abnormality is typically where patients see immediate improvement and also start seeing dramatic changes in their lifestyle. And so that's what we see reportedly the most. Beyond that bladder incontinence is probably 30 to 50 percent and cognitive improvement is probably around 50 to 60 percent as well.

Host: Wow. Those numbers are still fantastic considering those are very difficult symptoms to live with, especially in the elderly. What are the main surgical risks especially in the elderly that we see with these surgical treatments?

Kunal Vakharia, MD: Yeah part of it is the older the patient, the higher the risk from an anesthetic from any sort of procedure. But there are the obvious risks that we tell everyone. But the big ones in this situation are the risk of what we call a symptomatic ICH or hemorrhage because we are putting a catheter with navigation with a GPS system that we have in the OR, but it is still a semi blind procedure.

And then we add that with the fact that you have a risk of infection. And a risk of any sort of injury to the brain whenever that catheter is being placed. In the grand scheme of things, I'd say the risk to a procedure like this is probably closer to about 1 to 2 percent overall, and that includes that rate of infection, but mortality is pretty low.

Host: What about postoperative complications when we look at EVH or the shunting procedures? Could you highlight a few of those?

Kunal Vakharia, MD: Yeah, so complications after surgery from a shunt placement can be related to either over drainage, meaning we have a tube that's draining fluid from the brain, and we drain more than we initially anticipated, and that's part of the benefit of having these new valves. But in those situations, you can develop a blood clot that develops on the outside of the brain. It's like deflating a balloon a little bit. And so that's one potential risk, and that's what we call CSF overdrainage, but we have a lot of new devices, including anti-siphon devices and valves that help prevent that. Along with that, you always have that risk of infection, which is one of the things we always watch out for.

And then the last thing after surgery is, the shunt may actually fail. So they may actually see an immediate improvement, and then a couple weeks later, a tubing or something gets disconnected, we might see that their symptoms start to recur and we have to recognize when that happens.

Host: How often on those patients do you have to reoperate?

Kunal Vakharia, MD: It's not common. It's not common. Shunts in general have a pretty good durability and they last pretty well and they give these patients, particularly the elderly patients, a pretty good result.

Host: Well, you guys have really highlighted all of the clinical features of normopathic pressure hydrocephalus. Is USF involved in research specifically geared towards hydrocephalus?

Naomi Abel, MD: Yes, we are. There have been multiple prospective non randomized studies showing 60 to 85 percent improvement of patients with idiopathic NPH. However, until now, we've not been able to have a placebo controlled trial. Surgical studies, double blind studies are very difficult to design. However, now with the use of programmable valves, we have the ability to actually turn off a valve.

So, the study that we're involved in is a multi center study with the primary being at Johns Hopkins. We are one of 20 centers, 18 in the United States, one in Canada, one in Sweden in which patients are selected for surgery and have improved with the lumbar puncture. So they've been screened, they've been evaluated, they go to surgery.

All patients have the same surgery, but in half the patients we turn the valves on and in the other half we leave them off so that they are blinded for a total of three months. Only myself and the surgeon know which patients are on and which patients are off. So we do a lot of testing, particularly gait, bladder, cognitive testing during that time. And at the end of three months, all patients have their valves turned on.

Host: Well, thank you so much for this detailed information. Is there anything either of you would like to leave for the audience? And I'll start with you, Dr. Abel.

Naomi Abel, MD: We support the Hydrocephalus Association. which is probably the largest association in the world focused on patient education, focused on research. They have a bi annual conference. That conference is going to be in Tampa this July, and we look forward to being the host for the conference.

Host: Congratulations. That's wonderful. And Dr. Kunal Vakharia, would you like to leave any last minute tidbits of information on normal pressure hydrocephalus with our audience?

Kunal Vakharia, MD: It's not necessarily tidbits per se, but this field is evolving and it keeps on evolving with all the new technology coming out there. So definitely stay in tune and you'll see that there's a lot more non-invasive stuff that's going to happen in the future as well.

Host: Well thank you both so much for your time, and thank you to our audience for listening to MDCAST by Tampa General Hospital, which is available on all major streaming services for free. To collect your CME, please click on the link in the description. For other CME opportunities, including live webinars, on demand videos, and local events offered to you by Tampa General Hospital, please visit cme.tgh.org. I'm your host, Dr. Rania Habib, wishing you well.