Is Normal Pressure Hydrocephalus Hereditary?

Normal pressure hydrocephalus is not inherited the way conditions like cystic fibrosis or sickle cell disease are, where a single gene defect passes predictably from parent to child. But the evidence that genetics contribute to NPH risk has grown considerably over the past decade, with studies identifying familial clusters, candidate genes, and common genetic variants scattered across the genome. Roughly 10 to 16 percent of NPH patients have a close relative who also shows symptoms of the disease, which is lower than the family-history rates seen in Alzheimer’s or Parkinson’s but far higher than chance alone would predict.

How Often NPH Runs in Families

For a long time, NPH was assumed to be a sporadic condition, meaning it struck individuals without any clear family pattern. That assumption has been challenged by a growing number of case reports and cohort studies. A recent review tallied at least 32 families in which two or more members developed NPH, drawn from studies in Canada, Finland, Saudi Arabia, and Japan. In a Canadian cohort, about 10 percent of NPH patients had a first-degree relative with at least two of the classic NPH symptoms: gait problems, cognitive decline, and urinary incontinence. A larger Finnish cohort put the figure at 16 percent, with nearly 5 percent of those patients having a relative who had already undergone shunt surgery.¹

A family study that compared relatives of NPH patients against relatives of matched controls found a stark difference. Among first-degree relatives of NPH patients, about 7 percent had two or more progressive NPH-like symptoms, compared with less than 1 percent among relatives of control subjects. That translated to roughly an 11-fold increase in odds. Relatives of NPH patients also tended to develop gait problems and memory trouble at a younger age than relatives in the control group.²

These numbers are meaningful but still modest compared to better-known neurological diseases. Family-history rates for Parkinson’s disease hover around 20 to 25 percent, and for Alzheimer’s roughly 15 to 25 percent. NPH falls a tier below those, which partly explains why its genetic dimension has received less research attention. But the familial signal is real, and when one sibling is diagnosed, the report of two sisters with confirmed NPH has been cited as early evidence that genetic predisposition deserves serious investigation.³

Dominant Inheritance in Some Families

Among the families that do cluster, the inheritance pattern looks surprisingly clear in some cases. One Japanese family had four members across three generations who all developed NPH in later life, with the pattern consistent with autosomal dominant inheritance, meaning just one copy of the relevant gene variant was enough to confer susceptibility.⁴

The most comprehensive analysis to date assembled 30 familial NPH cases, combining 22 pedigrees from the published literature with 8 newly identified patients in a novel case series. The researchers concluded that the overall pattern was “highly suggestive” of autosomal dominant transmission. This subset of familial patients was notable for two features: they responded well to shunt surgery, and their brain tissue showed no signs of neurodegenerative pathology like Alzheimer’s-type plaques or tangles.⁵ That second point matters because many patients initially suspected of having NPH turn out to have an underlying neurodegenerative disease that mimics it. When that confusion is stripped away, the remaining “pure” NPH families show a cleaner genetic signal.

The practical implication of autosomal dominant transmission is that each child of an affected parent would have roughly a 50-50 chance of inheriting the predisposition. But inheriting the variant does not guarantee developing NPH. The condition typically appears in the 60s or later, and factors like vascular health, head injuries, and possibly infections all modify whether the genetic predisposition actually turns into disease. So even in these highly familial pedigrees, some carriers never develop symptoms.

Specific Genes That Have Been Linked to NPH

Researchers have taken several approaches to hunting for NPH-related genes. Some studies focus on rare families with dramatic inheritance patterns, while others scan the genomes of thousands of patients and controls looking for common variants. Both strategies have turned up leads, though no single “NPH gene” has emerged.

SFMBT1 Copy Number Variants

One of the more striking findings involves the SFMBT1 gene. A study of shunt-responsive NPH patients found that about 26 percent of them carried a specific copy number loss within this gene, compared with only about 4 percent of healthy elderly controls. That eight-fold increase in odds was also seen when compared against Parkinson’s disease patients, ruling out a nonspecific association with neurodegeneration in general.⁶ SFMBT1 encodes a protein involved in gene regulation, and the copy number deletion may alter how the brain handles cerebrospinal fluid dynamics, though the exact biological mechanism is still being worked out.

Genome-Wide Common Variants

A genome-wide association study using Finnish and UK Biobank data identified six genomic regions significantly associated with NPH. The strongest signal was near a gene called SLCO1A2, where carrying the protective variant reduced risk by roughly 30 percent. Other associated regions included AMZ1/GNA12, MLLT10, CDCA2, C16orf95, and PLEKHG1. When the analysis was restricted to confirmed idiopathic NPH cases only, four of the six signals held up.⁷ These are common variants, each contributing a small amount of risk on its own. In combination, they may help explain why certain people are more susceptible to NPH even without a strong family history.

CFAP43 and Cilia Defects

A different genetic thread involves motile cilia, the tiny hair-like structures lining brain ventricles that help move cerebrospinal fluid. Researchers identified a loss-of-function mutation in the CFAP43 gene that segregated with NPH in a family. When they knocked out the same gene in mice, the animals developed hydrocephalus along with visibly abnormal motile cilia.⁸ CFAP43 is better known for its role in sperm flagella, and mutations cause male infertility. The connection between sperm tails and brain ventricle cilia may seem odd, but the underlying molecular machinery is shared: both structures rely on the same set of proteins to beat rhythmically.

How These Genetic Defects Might Disrupt Brain Fluid Flow

NPH develops when cerebrospinal fluid fails to drain properly from the brain’s ventricles, causing them to expand and compress surrounding tissue. The question is what goes wrong at a cellular level, and several of the genes implicated in NPH converge on overlapping pathways.

Two genes, MPDZ and CCDC88C, both affect how cells lining the ventricles maintain their structure and polarity. MPDZ mutations weaken the junctions between these cells, while CCDC88C mutations compromise their internal scaffolding. The two proteins actually bind to each other, working together to inhibit a signaling pathway that keeps the cells properly oriented.⁹ When either gene is disrupted, cerebrospinal fluid circulation slows, and fluid accumulates. Mutations in CCDC88C have now been confirmed in four families with severe congenital hydrocephalus, where the condition appears at or before birth rather than in old age.¹⁰

Another piece of the puzzle involves aquaporin-4 (AQP4), a water channel protein found on star-shaped brain cells called astrocytes. In NPH patients, the density of AQP4 channels along blood vessels in the brain cortex is reduced compared to healthy individuals. These channels are thought to facilitate the glymphatic system, a waste-clearance network that flushes metabolic byproducts out of brain tissue while you sleep. When AQP4 is depleted, glymphatic flow may stall, contributing both to fluid buildup and to the accumulation of toxic proteins.¹¹ Whether AQP4 depletion is a cause or a consequence of NPH remains debated, but the finding fits neatly with the broader theme of impaired fluid dynamics.

Congenital Hydrocephalus Involves Different Genetics

It is worth separating NPH, which typically appears after age 60, from congenital hydrocephalus, which is present at or before birth. The two conditions share the basic problem of excess cerebrospinal fluid in the brain, but their genetic landscapes are quite different.

The best-understood genetic cause of congenital hydrocephalus is mutations in L1CAM, a gene on the X chromosome. These mutations account for an estimated 5 to 10 percent of male cases of isolated congenital hydrocephalus and cause a broader condition known as L1 syndrome, which can also include intellectual disability and limb abnormalities.¹² Because L1CAM sits on the X chromosome, the inheritance is X-linked: mothers can be asymptomatic carriers, and affected children are almost exclusively male.

Other congenital hydrocephalus genes, like CCDC88C discussed above, follow a recessive pattern, where a child must inherit faulty copies from both parents. None of these congenital-onset genes have been convincingly linked to the late-life form of NPH. So if your family has a history of a baby born with hydrocephalus, that does not by itself raise your risk for NPH in your 70s. The conditions may share some molecular plumbing, but the genetic wiring is largely distinct.

What Family History Means for Outcomes

One finding that clinicians are starting to pay attention to is that familial NPH patients may have a worse cognitive trajectory than those with sporadic disease. In the Finnish cohort, patients with a family history of NPH had up to a three-fold higher risk of clinical dementia compared to those without affected relatives.¹ This could mean that the genetic variants driving familial NPH also affect brain resilience in ways that go beyond fluid dynamics alone, or it could simply reflect that familial cases tend to be diagnosed later because neither the patient nor the doctor initially suspects a “non-hereditary” condition.

On the flip side, the familial cases analyzed in the autosomal dominant pedigrees tended to respond well to shunt surgery and lacked Alzheimer’s-type pathology.⁵ That is encouraging because one of the biggest clinical challenges in NPH is distinguishing patients who will benefit from a shunt from those whose symptoms are really driven by neurodegeneration. A positive family history for NPH, especially if other relatives improved after shunting, could eventually serve as one clue that shunting is likely to help.

Why NPH Is Probably Both Genetic and Environmental

The emerging picture is that NPH falls into a category alongside conditions like type 2 diabetes or high blood pressure: there is genuine genetic susceptibility, but it interacts with environmental and lifestyle factors to determine who actually develops the disease. Vascular risk factors like hypertension and diabetes are themselves associated with NPH, and so are prior head injuries. Many NPH patients also have white matter disease visible on brain imaging, which is influenced by cardiovascular health. A person who inherits risk variants near SLCO1A2 or carries an SFMBT1 copy number loss might never develop NPH if they maintain good vascular health, or they might develop it decades earlier if they also have uncontrolled blood pressure.

The heterogeneity of NPH genetics reflects this complexity. Some families show clear dominant inheritance of what appears to be a single strong-effect gene variant. Others contribute to the common, polygenic end of the spectrum, where dozens of small-effect variants scattered across the genome collectively raise risk by a modest amount. And many patients fall in between or have no identifiable genetic component at all. One review characterized the situation well: familial hydrocephalus has heterogeneous causes that may result from either monogenic or multifactorial mechanisms, and distinguishing these in an individual patient remains difficult.

Should You Worry if a Parent Had NPH?

There is no genetic test currently available for NPH risk, and no clinical guideline recommends screening relatives of NPH patients. That said, being aware of a family history is worthwhile for a practical reason: NPH is widely underdiagnosed. The classic triad of walking difficulty, cognitive changes, and bladder control problems develops gradually and is easily attributed to “normal aging” or other conditions like Parkinson’s or Alzheimer’s. If you know a parent or sibling was diagnosed with NPH, you might recognize the early signs more quickly in yourself and seek evaluation sooner.

Given that relatives of NPH patients show symptoms at a younger age, the window for early intervention could be meaningful. Shunt surgery is most effective when performed before significant brain tissue damage has accumulated, and the cognitive deficits of NPH, unlike those of true Alzheimer’s, are at least partially reversible with treatment. No one should panic over a single relative with NPH. But filing it away as a possibility, the way you would a family history of heart disease, is reasonable.

MicroRNAs and the Future of Molecular Diagnosis

One area of active research is whether molecular biomarkers in cerebrospinal fluid can help distinguish NPH from conditions that mimic it, like Parkinson’s disease or Alzheimer’s. This matters because misdiagnosis is common: patients referred for NPH evaluation sometimes turn out to have a neurodegenerative disease, and vice versa. A study examining small RNA molecules called microRNAs found that one in particular, miR-4274, was significantly decreased in the cerebrospinal fluid of patients with Parkinson’s-like syndromes compared to those with confirmed NPH. The difference was large enough to separate the two groups with high accuracy.¹³

MicroRNAs regulate gene expression without changing the DNA sequence itself, making them part of the broader epigenetic layer that sits between genetics and environment. Their potential value in NPH goes beyond diagnosis. Researchers have proposed that microRNAs, along with metabolomic profiles and extracellular vesicles in cerebrospinal fluid, could eventually reveal whether a patient’s NPH has a strong genetic component, predict their response to shunting, or monitor disease progression over time.¹⁴ None of these tools is ready for routine clinical use, but they represent a shift toward understanding NPH at a molecular level rather than relying solely on brain imaging and symptom checklists.