Snapshot A 71-year-old man presents to his neurologist for gait difficulties. He is accompanied by his wife who said that he takes short steps and has had episodes of urinary incontinence. He denies any head trauma or recent infectious symptoms. Physical examination is notable for magnetic gait; however, the rest of the neurological assessment is unremarkable. An MRI brain is performed, which demonstates ventricular enlargement without ischemic changes. He undergoes a large volume lumbar puncture, and 45 minutes after the tap his gait significantly improves. He is referred to neurosurgery for ventricular shunting. Introduction Definition a form of communicating hydrocephalus leading to pathologically enlarged ventricles with normal opening pressure on lumbar puncture Associated conditions Alzheimer disease vascular dementia Epidemiology Incidence idiopathic normal pressure hydrocephalus (NPH) is more common in elderly patients Etiology Idiopathic Secondary causes include subarachnoid hemorrhage meningitis traumatic brain injury neurosurgery brain radiation Pathogenesis Unknown in idiopathic cases In secondary NPH cases reduced cerebrospinal fluid reabsorption secondary to inflammation and subsequent fibrosis of the arachnoid granulations and/or base of the brain Presentation Symptoms cognitive disturbances (occurs months to years after gait dysfunction) impaired executive function (found early) poor attention and concentration psychomotor slowiing apathy Physical exam gait dysfunction wide-based magnetic gait ("glue-footed") urinary incontinence typically urinary urgency first Imaging MRI brain indication superior to CT scan in the evaluation of NPH findings ventriculomegaly (hallmark finding) periventricular white matter changes Studies High-volume lumbar puncture assess gait before the lumbar puncture (LP) and 30-60 minutes after the LP Differential Parkinson disease differentiating factors patients have a resting tremor, bradykinesia, and rigidity Vascular dementia differentiating factors patients have ischemic changes on MRI brain Treatment Operative ventricular shunting indication treatment of choice in patients with clinical and imaging findings of NPH Complications Falls