Addressing the Devil Within: Normal Pressure Hydrocephalus—A Narrative Review

Abstract Normal pressure hydrocephalus (NPH) is the most frequently occurring form of hydrocephalus among adults. It is characterized clinically by the classical triad, called Hakim's triad, comprising gait issues, cognitive impairment, and urinary problems. NPH may be primary or idiopathic (iNPH) or secondary. Characteristic neuroimaging features occur, which are vital to diagnosis. Diagnostic criteria in the form of Japanese guideline and Congress of Neurological Surgeons 2005 guidelines have been devised, and broadly, are based on a constellation of clinical and neuroimaging features, in association with cerebrospinal fluid (CSF) testing. CSF tap test, extended lumbar drainage, and CSF infusion tests are invasive diagnostic tests. CSF tap test and extended lumbar drainage are used to demonstrate clinical reversibility with CSF drainage, and patients who demonstrate this are candidates for CSF shunting. However, due to the low negative predictive value of these tests, potential response to shunting cannot be negated among patients who do not respond to CSF drainage. Various shunting procedures are used for treatment, including ventriculoperitoneal, lumboperitoneal, and ventriculoatrial shunts. Endoscopic third ventriculostomy has also been attempted with limited success. Among the clinical features, gait abnormalities are most responsive to shunting. Persistent long-term response to shunting has been reported. Patients need to be meticulously followed up after the shunting procedure, to assess clinical and neuroimaging response, and detect possible shunt-related complications, especially CSF over-drainage. Early treatment is associated with better prognosis, and it is crucial to recognize and treat this condition before the development of severe symptoms.