Periods of excessive amounts of cerebrospinal fluid pressure in and around the brain, despite a normal average pressure of the fluid, have been felt to be a cause of NPH. A clinical concern regarding reasons for referral to a neurologist or neurosurgeon is that normal pressure hydrocephalus is commonly an incidental diagnosis made or mentioned as a differential by a radiologist when interpreting the relative quantity of CSF volume on a CT or MRI scan made for symptoms different than those of NPH itself.
The past published practice standard of the American Academy of Neurology on surgical shunt placement as treatment of normal hydrocephalus has been to refer patients for neurosurgical intervention with shunting if the patient or family desire. What counseling is best regarding the risks and benefits of such surgery has not been clear. This new trial is quite important, since it suggests that such patients can be told there might be a small improvement in gait from the surgery, but that cognition and incontinence issues are unlikely to improve from shunting surgery. In addition, there is a substantial risk of complicating subdural hematoma (internal bleeding around the brain) according to this new study.
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A Randomized Trial of Shunting for Idiopathic Normal-Pressure Hydrocephalus
Authors: Mark G. Luciano, M.D., Ph.D. https://orcid.org/0000-0002-5664-2956, Michael A. Williams, M.D. https://orcid.org/0000-0002-7284-8014, Mark G. Hamilton, M.D., C.M. https://orcid.org/0000-0002-3380-8829, Heather L. Katzen, Ph.D. https://orcid.org/0009-0001-7297-9380, Nickolas A. Dasher, Ph.D. https://orcid.org/0000-0001-5858-5265, Abhay Moghekar, M.B., B.S. https://orcid.org/0000-0001-9464-1551, Jun Hua, Ph.D. https://orcid.org/0000-0001-5481-7380, +13 , for the PENS Trial Investigators and the Adult Hydrocephalus Clinical Research Network*Author Info & Affiliations
Published September 16, 2025
DOI: 10.1056/NEJMoa2503109
Copyright © 2025
Background
Idiopathic normal-pressure hydrocephalus is a neurologic disorder characterized by impaired gait, balance, cognition, and bladder control in older adults. The disorder is treated with shunt surgery, but the effectiveness of shunting is unclear.
Methods
We conducted a double-blind, randomized, placebo-controlled trial involving participants selected for shunt surgery on the basis of gait-velocity improvement with cerebrospinal fluid (CSF) drainage. Participants were randomly assigned to an open-shunt valve setting (opening pressure, 110 mm of water) or a placebo valve setting (opening pressure, >400 mm of water) of a noninvasively adjustable shunt. The primary outcome was the change in gait velocity 3 months after surgery. Secondary outcomes were the change at 3 months in the Tinetti scale total score (range, 0 to 28; lower scores indicate worse gait and balance), Montreal Cognitive Assessment (MoCA) score (range, 0 to 30; lower scores indicate worse cognition), and Overactive Bladder Questionnaire score (range, 0 to 100; higher scores indicate worse urinary incontinence).
Results
A total of 99 participants underwent randomization and received the assigned intervention. At 3 months, gait velocity had increased in the open-shunt group (mean [±SD] change, 0.23±0.23 m per second; assessed in 49 participants) and was unchanged in the placebo group (mean change, 0.03±0.23 m per second; assessed in 49 participants), resulting in a treatment difference of 0.21 m per second (95% confidence interval, 0.12 to 0.31; P<0.001). A significantly greater improvement in the open-shunt group than the placebo group was seen for the Tinetti scale score (mean change, 2.9 points vs. 0.5 points; P=0.003) but not the MoCA score (1.3 points vs. 0.3 points) or the Overactive Bladder Questionnaire score (−3.3 points vs. −1.5 points). The results regarding adverse events were mixed, with more participants in the placebo group reporting falls (46% vs. 24%), an equal percentage having cerebral bleeding (2% in both groups), and more participants in the open-shunt group having subdural bleeding (12% vs. 2%) and positional headaches (59% vs. 28%).
Conclusions
Among participants with idiopathic normal-pressure hydrocephalus who had a response to temporary CSF drainage, shunting resulted in significant improvements at 3 months in gait velocity and a measure of gait and balance but not in measures of cognition or incontinence. (Funded by the National Institute of Neurological Disorders and Stroke and the Trial Innovation Network; PENS ClinicalTrials.gov number, NCT05081128.)
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