Normal Pressure Hydrocephalus: The Brain Condition Often Mistaken for Dementia
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Normal pressure hydrocephalus, or NPH, is a neurological condition caused by a buildup of cerebrospinal fluid in the brain's ventricles. The fluid accumulates faster than the body can absorb it, and the ventricles expand and press on surrounding brain tissue (National Institute of Neurological Disorders and Stroke, NINDS).
Cerebrospinal fluid normally cushions the brain and spinal cord and is continuously produced and reabsorbed in a steady cycle. In NPH, that cycle breaks down. Despite the name, the pressure inside the skull often measures within a normal range on standard testing, which is part of why the condition is so frequently missed (NINDS; Cleveland Clinic).
Who It Affects
NPH is most common in adults over 60, and incidence rises with age. Yale Medicine estimates that more than 700,000 Americans have NPH, and fewer than 20 percent are correctly diagnosed. Most cases have no identifiable cause and are labeled idiopathic NPH. A smaller number develop after a brain hemorrhage, head injury, infection, tumor, or brain surgery, a form sometimes called secondary NPH (NINDS).
The Three Hallmark Symptoms
Clinicians look for a triad of symptoms, though not everyone presents with all three at the same time or severity.
- Gait disturbance: a wide-based, shuffling walk, often the earliest and most noticeable symptom
- Cognitive changes: slowed thinking, memory difficulty, and trouble with attention or planning
- Urinary incontinence: urgency or loss of bladder control, typically appearing later than the other two
This combination is why NPH is so often confused with Alzheimer's disease or another form of dementia. The cognitive symptoms can look similar, and the condition is sometimes referred to informally as a "treatable dementia" because, unlike Alzheimer's, NPH symptoms can improve or reverse with proper treatment when it's caught in time (Cleveland Clinic; Hydrocephalus Association).
How It's Diagnosed
Diagnosis typically starts with brain imaging, an MRI or CT scan, to look for enlarged ventricles out of proportion to any brain atrophy. Because imaging alone isn't definitive, many centers use a high-volume spinal tap or a temporary lumbar drain: removing a measured amount of cerebrospinal fluid and then assessing whether walking and cognitive symptoms improve in the following hours or days. A positive response helps predict whether a permanent treatment will help (Halperin et al., Neurology, 2015).
Treatment
The standard treatment is surgical placement of a ventriculoperitoneal shunt, a thin tube that drains excess fluid from the brain's ventricles to the abdominal cavity, where the body reabsorbs it. The shunt includes an adjustable valve that a physician can tune over time as a patient's needs change. A less common alternative is endoscopic third ventriculostomy, in which a surgeon creates a small opening to allow fluid to bypass the blockage (NINDS).
Recovery after shunt surgery is gradual. Many patients see improvement in gait and cognition over the following months as fluid pressure normalizes, though outcomes vary and are generally best when the condition is identified early, before prolonged pressure causes lasting damage to brain tissue (Halperin et al., Neurology, 2015).
Why It Matters for Caregivers
If a loved one has been told they have dementia, and something about the picture doesn't quite fit, a gait change that came on before the memory problems, or incontinence that showed up early, it's worth asking a doctor directly whether NPH has been ruled out. It is underdiagnosed partly because its symptoms overlap so heavily with more familiar conditions, and partly because clinicians who aren't specifically looking for it may not order the imaging or spinal tap needed to catch it.
A misdiagnosis of irreversible dementia, when the real cause is treatable, costs a family time they cannot get back. Asking the question costs nothing.
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Sources: National Institute of Neurological Disorders and Stroke (NINDS), Hydrocephalus Information Page. Cleveland Clinic, Normal Pressure Hydrocephalus overview. Yale Medicine, Normal Pressure Hydrocephalus patient education page. Hydrocephalus Association, patient and family resources. Halperin JJ, Kurlan R, Schwalb JM, Cusimano MD, Schoenberg BS, Judson I, et al. "Practice guideline: Idiopathic normal pressure hydrocephalus." Neurology. 2015;85(23):2063-2071.