Normal Pressure Hydrocephalus (NPH / iNPH)

Our Specialists for Normal Pressure Hydrocephalus (NPH / iNPH)

NPH is one of the few neurodegenerative-looking syndromes that can be genuinely reversed — but only if it's correctly identified and treated by a team that sees it often. Our neurosurgeons and neurologists work together on the full workup, from the high-volume lumbar tap test to programmable-valve shunt placement and long-term valve tuning.

Paramita Das, M.D., M.S.

Director, Neurotrauma; Director, Neurosurgical Trauma Fellowship

Dr. Das is Director of Neurotrauma at UChicago's Level 1 Trauma Center and directs the Neurosurgical Trauma Fellowship, one of only a few dedicated neurosurgical trauma fellowships in the country. She manages both head trauma and acute spine pathology and has been named to the Bucksbaum-Siegler Institute for Clinical Excellence. She trained at the University of Minnesota for residency and completed a skull base fellowship at Cleveland Clinic. Dr. Das runs the NPH evaluation pathway at UChicago — she sees a high volume of tap-test referrals, coordinates external lumbar drainage trials for ambiguous cases, and performs VP shunt placement with a programmable valve for patients whose gait or cognition improves with drainage.

P. B. Raksin, M.D.

Associate Program Director, Neurological Surgery Residency

Dr. Raksin is an Associate Professor of Neurological Surgery and serves as Associate Program Director of the UChicago Neurological Surgery residency program. She is a senior clinician within the department and contributes broadly to resident education and general neurosurgical care. Dr. Raksin's practice focuses heavily on adult hydrocephalus and CSF disorders, including idiopathic NPH and secondary NPH after subarachnoid hemorrhage or trauma; she manages shunt placement, long-term valve adjustment, and revisions when they're needed.

Peter Christian Warnke, M.D.

Section Chief, Functional Neurosurgery & Epilepsy

Dr. Warnke is an international leader in functional neurosurgery and has performed over 6,000 stereotactic surgeries and more than 3,000 brain tumor surgeries. He is only the second neurosurgeon worldwide to perform laser hemispherotomy, and he has completed over 400 laser ablation surgeries since arriving at UChicago. He is funded by four NIH grants including the BRAIN Initiative, and he directs the NAUTILUS trial for thalamic stimulation in drug-resistant epilepsy. For patients where the NPH picture is complicated by coexisting ventricular anatomy or prior surgery, Dr. Warnke brings a stereotactic and image-guided approach to shunt catheter placement — his broader work on precision neurosurgery means ventricular catheters are placed exactly where they need to go.

What Is Normal Pressure Hydrocephalus?

Normal pressure hydrocephalus (NPH) is a condition in which the fluid-filled spaces inside your brain — called ventricles — become enlarged even though the pressure of the fluid measures in the normal range. The extra fluid stretches and disrupts the brain tissue around the ventricles, producing a very specific set of problems: a slow, unsteady walk, trouble with memory and thinking, and loss of bladder control. Together, these three are known as the Hakim triad, after the Colombian neurosurgeon Salomón Hakim who first described the syndrome with Raymond Adams in 1965.

The tricky part is that those three symptoms overlap with the two most common conditions of later life: Parkinson's disease and Alzheimer's disease. Many people with NPH are first told they have one of those — or simply told that this is what aging looks like. The difference matters enormously, because NPH is one of the few dementia-like syndromes that can actually be reversed with surgery.

NPH mostly affects people over 60. It's uncommon but not rare — most estimates suggest somewhere between 0.5% and 3% of adults over 65 have it, and the number rises steeply with age. Because it's so often missed, the true number is probably higher than what's in the medical literature.

What Does It Feel Like?

Most people with NPH develop their symptoms slowly, over months to a few years. The three parts of the triad usually do not show up at the same time — gait trouble almost always comes first, and it's also the symptom that responds best to treatment.

The walk changes first

The walking problem in NPH is distinctive. Patients and families often describe it as:

• A "magnetic" gait — feet feel stuck to the floor, as if there were magnets in the soles
• Short, shuffling steps with a wide base
• Trouble starting — the first step feels frozen
• Difficulty turning; patients pivot in many small steps rather than one smooth turn
• Falls backward, or a feeling of being pulled backward
• Legs that feel heavy, weak, or uncoordinated even though strength on exam is normal

This is different from a Parkinson's walk (usually more stooped, with tremor and smaller arm swing) and different from an arthritis walk (which hurts). NPH gait does not hurt — it just doesn't work.

Memory and thinking slow down

• Slower processing — it takes longer to find a word or answer a question
• Trouble with attention and concentration
• Apathy and loss of drive that family members sometimes mistake for depression
• Short-term memory gaps, though classic "can't remember who you are" dementia is uncommon in pure NPH

Bladder control fails

• Urinary urgency — having to go right now
• Frequency, especially at night
• Frank incontinence in later stages
• In advanced disease, some patients lose awareness that they need to go at all

If you or a family member has more than one of these at the same time — particularly the walking change — it is worth asking your doctor specifically about NPH.

How Is It Diagnosed?

Diagnosing NPH takes more than a single test. It's a combination of your symptoms, brain imaging, and a physiologic test that shows your walking or thinking gets better when spinal fluid is drained.

Brain MRI (or CT)

The first step is an MRI of the brain. In NPH, the ventricles are enlarged out of proportion to any brain shrinkage. Radiologists measure this with the Evans index — the ratio of the widest part of the frontal horns to the widest part of the skull — and a value greater than 0.3 is one criterion for the diagnosis.

But the more specific imaging clue is called DESH, short for disproportionately enlarged subarachnoid space hydrocephalus. On MRI, patients with DESH show three things at once: enlarged ventricles, widened Sylvian fissures (the deep grooves on the sides of the brain), and tightly crowded sulci over the top of the head. That unusual combination — lots of fluid in some places, almost none in others — is a strong sign that the problem is NPH rather than generalized brain atrophy. Patients with a clear DESH pattern are significantly more likely to respond to a shunt.

High-volume lumbar tap test

Imaging alone is not enough to commit someone to surgery. The next step is usually a high-volume lumbar tap — a spinal tap in which we drain 30-50 mL of cerebrospinal fluid through a lumbar needle, the same kind used for a standard LP. Before and after the tap, we carefully measure your walking (often with a timed up-and-go test) and test your thinking.

If your gait or cognition clearly improves in the hours to day after the tap, that's a strong argument for going ahead with shunt surgery. A positive tap test has a very high positive predictive value — in studies it exceeds 90% — meaning if you improve, a shunt is very likely to help. A negative tap test is less reliable: many people who don't improve after a single tap still benefit from a shunt, because not enough fluid was drained for long enough.

External lumbar drainage

For patients where the picture isn't clear after a single tap, we use external lumbar drainage (ELD). A thin catheter is placed in the lumbar spinal fluid space and left in for about 2-3 days in the hospital. During that time, 10-15 mL of fluid drains off every hour, and physical and occupational therapy reassess walking and cognition daily. ELD is more invasive than a tap, but it's a more sensitive test — in published series, about 85-95% of patients who improve on ELD go on to improve after shunt surgery.

Ruling out mimics

Because the symptoms overlap so much with Parkinson's disease, Alzheimer's disease, vascular dementia, cervical myelopathy, and B12 deficiency, a careful evaluation also includes a neurologic exam, blood work, and sometimes formal neuropsychological testing. Getting the diagnosis right is the whole game.

Types of NPH

Idiopathic NPH (iNPH)

The most common form — idiopathic means we don't know why it started. It typically appears in people over 60, builds gradually over months to years, and is the form that most of the research and guidelines focus on. When people say "NPH," they usually mean iNPH.

Secondary NPH

In secondary NPH, something specific interfered with the way your brain normally absorbs spinal fluid. Common causes include:

• A previous subarachnoid hemorrhage, often from a ruptured aneurysm, that left behind blood and scarring in the spinal-fluid pathways
• A previous traumatic brain injury
• Past meningitis or other central nervous system infection
• A previous brain surgery, especially for a tumor near the ventricles

Secondary NPH often shows up at a younger age than iNPH and may develop weeks to years after the inciting event. In general, secondary NPH responds to shunting at higher rates than idiopathic NPH, because the mechanism is more clear-cut. The workup and the surgery itself, however, are essentially the same.

How Is It Treated?

NPH is treated surgically, by diverting extra spinal fluid out of the brain. There is no medication that reverses NPH — the core problem is mechanical, and the fix is mechanical.

Ventriculoperitoneal (VP) shunt with a programmable valve

The standard operation is a ventriculoperitoneal (VP) shunt. A soft silicone catheter is placed through a small hole in the skull into one of the ventricles, connected to a valve behind the ear, and then tunneled under the skin of the neck and chest down into the abdominal cavity, where the extra fluid is harmlessly reabsorbed. The surgery takes about an hour, is done under general anesthesia, and most patients go home within 1-3 days.

Modern NPH shunts use a programmable valve — meaning the opening pressure of the valve can be adjusted non-invasively, by holding a magnetic tool over the skin behind the ear. This matters because the "right" amount of drainage is different for every patient and often needs fine-tuning in the months after surgery. Too little drainage, and symptoms don't improve; too much drainage, and fluid can collect on the surface of the brain (a subdural hygroma or hematoma). A programmable valve lets us adjust the setting in clinic, without another operation, if problems come up.

Lumboperitoneal (LP) shunt

In selected patients — particularly those whose ventricles are not large enough to safely catheterize — we place a lumboperitoneal shunt instead, with the proximal catheter in the lumbar thecal sac rather than the ventricle. The SINPHONI-2 trial in Japan showed lumboperitoneal shunting is an effective option for iNPH in carefully selected patients.

What to expect after surgery

• Gait is usually the first thing to get better — often within days to weeks
• Urinary control tends to improve next, over weeks to months
• Cognitive improvement is the slowest and the most variable, and it depends heavily on how much coexisting Alzheimer's-type disease is present
• Valve adjustments may be needed in the first 6-12 months as we find the right setting
• Physical therapy after shunting is very important — the brain has to relearn how to walk normally

Risks

VP shunting is generally safe, but it is still surgery. The main risks include infection (around 3-5%), shunt malfunction requiring a revision, subdural fluid collections from over-drainage, and bleeding. A published American Academy of Neurology systematic review found a serious adverse event rate of about 11% in the first few months after shunting. Programmable valves have reduced overdrainage problems substantially compared with the older fixed-pressure valves.

What Are the Outcomes?

For patients who are carefully selected — meaning the right clinical picture, the right MRI pattern, and a positive response to tap test or external lumbar drainage — a shunt for NPH is one of the more gratifying operations in neurosurgery. Most people improve, and the improvement often lasts for years.

Across published series, shunt surgery helps roughly 70-80% of properly selected iNPH patients in the first year. A large systematic review of shunt outcomes reported an average improvement rate of 71% across all studies — and 82% in studies published in the most recent era, reflecting better patient selection and programmable-valve technology. The American Academy of Neurology's 2015 practice guideline concluded that shunting produces subjective improvement in roughly 96% of patients and objective improvement on a timed walking test in about 83% at 6 months.

What predicts a good result?

• A clear DESH pattern on MRI
• A positive tap test or a positive external lumbar drainage trial
• Gait problems as the dominant symptom — those patients do best
• Shorter duration of symptoms before surgery (years-long untreated NPH is harder to reverse)
• Fewer coexisting vascular or Alzheimer's-type changes on MRI

Even patients whose symptoms came on slowly over years can benefit. But getting treated earlier — before falls, injuries, and full-time care become part of the picture — leads to bigger, longer-lasting improvement. The most important thing you can do is to get an accurate diagnosis from a team that evaluates and treats NPH regularly.

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