Normal Pressure Hydrocephalus

Normal pressure hydrocephalus (NPH) is a condition, most common in older adults, in which cerebrospinal fluid (CSF), the fluid that normally surrounds and cushions the brain and spinal cord, builds up in the brain’s fluid-filled chambers (the ventricles), causing them to enlarge. Despite this build-up, the fluid pressure measured on a standard test is often within, or close to, the normal range, which is where the condition gets its somewhat misleading name.

NPH is frequently under-recognized because its symptoms overlap with other, more common conditions of aging, including Parkinson’s disease and other causes of memory decline. Correctly identifying NPH matters because, unlike most causes of cognitive decline in older adults, a meaningful proportion of patients improve with treatment.

NPH is classically associated with three groups of symptoms, though not every patient has all three, and they may not all appear at the same time:

• Gait disturbance: a broad-based, shuffling, or “stuck to the floor” walking pattern, often with difficulty turning; this is typically the earliest symptom and the one most likely to improve with treatment
• Cognitive decline: slowed thinking, reduced attention and difficulty with planning and organizing, which can resemble other forms of dementia
• Urinary symptoms: urgency and, later, incontinence

Diagnosis combines the clinical pattern of symptoms with brain imaging showing enlarged ventricles out of proportion to any shrinkage of the brain’s surface, and, in most cases, a CSF tap test: a controlled, larger-volume lumbar puncture in which a measured amount of spinal fluid is removed, with gait and, where relevant, cognition assessed before and shortly afterward. Improvement following the tap test supports the diagnosis and is a reasonably good predictor of benefit from shunt surgery. A tap test that does not show clear improvement does not completely rule out benefit from surgery either, and in some cases an extended period of spinal fluid drainage over several days is used when a single tap test is inconclusive; this nuance is discussed individually rather than treated as a strict pass-or-fail test.

Shunt surgery is generally considered once the diagnosis of NPH is reasonably well supported by the pattern of symptoms, imaging, and, typically, a positive response to a tap test (or extended drainage trial), and the patient’s overall health is suitable for a shunt procedure.

The standard treatment is a ventriculoperitoneal (VP) shunt; a thin tube that continuously drains excess fluid from the brain to another part of the body, where it is reabsorbed. Full detail on the shunt procedure, the adjustable valve, and follow-up is provided on our VP Shunt Surgery page.

• Detailed history and neurological examination, including formal gait assessment
• Cognitive assessment
• Brain MRI or CT, assessing ventricle size and other supporting imaging features
• CSF tap test, or an extended lumbar drainage trial where appropriate
• General health assessment for a shunt procedure

Gait is the symptom most likely to improve, often the most noticeably and the most quickly, after shunt surgery. Urinary symptoms and cognitive function may also improve, but less predictably and often less completely than gait. Treatment goals vary between patients: for some, the aim is regaining safe, independent walking; for others, particularly with more established cognitive decline, the aim is a more modest but still meaningful improvement in function. Shunt surgery is not presented as reversing all symptoms or as a treatment for other causes of dementia that may coexist with NPH.

Risks include infection, shunt blockage or other mechanical problems requiring a further procedure, and, because the valve controls how much fluid drains, either over-drainage (which can rarely cause bleeding around the brain’s surface) or under-drainage (insufficient symptom improvement); both of which are managed by adjusting the valve setting. Because NPH often occurs in older adults who may have other age-related conditions, some symptoms may not improve fully even with a well-functioning shunt.

Most patients stay in hospital for a short period after surgery for initial recovery and imaging to confirm shunt position. The valve setting is checked and adjusted during follow-up as needed, based on symptom response. Full detail on ongoing shunt care, valve adjustment and MRI precautions is provided on the VP Shunt Surgery page.