Normal pressure hydrocephalus (NPH) is a clinical syndrome of gait abnormality, cognitive impairment, and urinary incontinence. Evaluation of CSF dynamics, patterns of fludeoxyglucose (FDG) uptake, and patterns of brain stiffness may aid in the evaluation of challenging cases that lack typical clinical and structural radiographic features.

In this episode, Katie Grouse, MD, FAAN, speaks with Aaron Switzer, MD, MSc, author of the article "Radiographic Evaluation of Normal Pressure Hydrocephalus" in the Continuum® June 2025 Disorders of CSF Dynamics issue.

Dr. Grouse is a Continuum® Audio interviewer and a clinical assistant professor at the University of California San Francisco in San Francisco, California.

Dr. Switzer is a clinical assistant professor of neurology in the department of clinical neurosciences at the University of Calgary in Calgary, Alberta, Canada.

Additional Resources

Read the article: Radiographic Evaluation of Normal Pressure Hydrocephalus

Subscribe to Continuum®: shop.lww.com/Continuum

Earn CME (available only to AAN members): continpub.com/AudioCME

Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud

More about the American Academy of Neurology: aan.com

Social Media

facebook.com/continuumcme

@ContinuumAAN

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast.

Dr Grouse: This is Dr Katie Grouse. Today I'm interviewing Dr Aaron Switzer about his article on radiographic evaluation of normal pressure hydrocephalus, which he wrote with Dr Patrice Cogswell. This article appears in the June 2025 Continuum issue on disorders of CSF dynamics. Welcome to the podcast, and please introduce yourself to our audience.

Dr. Switzer: Thanks so much for having me, Katie. I'm a neurologist that's working up in Calgary, Alberta, Canada, and I have a special interest in normal pressure hydrocephalus. So, I'm very happy to be here today to talk about the radiographic evaluation of NPH.

Dr Grouse: I'm so excited to have you here today. It was really wonderful to read your article. I learned a lot on a topic that is not something that I frequently evaluate in my clinic. So, it's really just a pleasure to have you here to talk about this topic. So, I'd love to start by asking, what is the key message that you hope for neurologists who read your article to take away from it?

Dr. Switzer: The diagnosis of NPH can be very difficult, just given the clinical heterogeneity in terms of how people present and what their images look like. And so, I'd like readers to know that detailed review of the patient's imaging can be very helpful to identify those that will clinically improve with shunt surgery.

Dr Grouse: There's another really great article in this edition of Continuum that does a really great job delving into the clinical history and exam findings of NPH. So, I don't want to get into that topic necessarily today. However, I'd love to hear how you approach a case of a hypothetical patient, say, where you're suspicious of NPH based on the history and exam. I'd love to talk over how you approach the imaging findings when you obtain an MRI of the brain, as well as any follow-up imaging or testing that you generally recommend.

Dr. Switzer: So, I break my approach down into three parts. First, I want to try to identify ventriculomegaly and any signs that would support that, and specifically those that are found in NPH. Secondly, I want to look for any alternative pathology or evidence of alternative pathology to explain the patient's symptoms. And then also evaluate any contraindications for shunt surgery. For the first one, usually I start with measuring Evans index to make sure that it's elevated, but then I want to measure one of the other four measurements that are described in the article, such as posterior colossal angle zed-Evans index---or z-Evans index for the American listeners---to see if there's any other features that can support normal pressure hydrocephalus. It's very important to identify whether there are features of disproportionately enlarged subarachnoid space hydrocephalus, or DESH, which can help identify patients who may respond to shunt surgery. And then if it's really a cloudy clinical picture, it's complicated, it's difficult to know, I would usually go through the full evaluation of the iNPH radscale to calculate a score in order to determine the likelihood that this patient has NPH. So, the second part of my evaluation is to rule out evidence of any alternative pathology to suggest another cause for the patient's symptoms, such as neurodegeneration or cerebrovascular disease. And then the third part of my evaluation is to look for any potential contraindications for shunt surgery, the main one being cerebral microbleed count, as a very high count has been associated with the hemorrhagic complications following shunt surgery.

Dr Grouse: You mentioned about your use of the various scales to calculate for NPH, and your article does a great job laying them out and where they can be helpful. Are there any of these scales that can be reasonably relied on to predict the presence of NPH and responsiveness to shunt placement?

Dr. Switzer: I think the first thing to acknowledge is that predicting shunt response is still a big problem that is not fully solved in NPH. So, there is not one single imaging feature, or even combination