Time to Reconsider the Value of Shunting Procedures for "Idiopathic Normal Pressure Hydrocephalus"

The concept of "normal pressure hydrocephalus" dates back to the description by Hakim and Adams in 1965 of 2 series of patients with enlarged lateral ventricles, high normal cerebral spinal fluid (CSF) pressure and a triad of cognitive impairment, urinary incontinence, and gait apraxia. The validity of this concept is based upon the reversal of its symptoms by a shunting procedure. However, all of these patients had secondary communicating hydrocephalus after previous episodes of meningitis, brain trauma, or subarachnoid hemorrhage. Nevertheless, shunting procedures for "idiopathic normal pressure hydrocephalus" with similar symptoms but no antecedent cause for communicating hydrocephalus became widely performed, although they were not tested by randomized, placebo-controlled trials for their value until a series of recent publications. These trials do not find improvement in either cognitive function or continence after shunting, and show that there is a small (approximately 25%) improvement in gait speed. They also confirm earlier studies that these patients suffer an approximately 10 to 15% incidence of severe adverse events in the first year after shunting, which may further accumulate with time. In the absence of value for shunting in reversing cognitive impairment and incontinence, the entire concept of "idiopathic normal pressure hydrocephalus" is called into question. ANN NEUROL 2026;99:838-843.