When to consider normal pressure hydrocephalus in the patient with gait disturbance.

Normal pressure hydrocephalus (NPH) is a chronic adult disorder of unknown cause. It is characterized by gradual onset of gait impairment, cognitive dysfunction, and urinary incontinence in the presence of enlarged ventricles. NPH is a relatively rare cause of these 3 common symptoms. Diagnosis is made based on suspicion of NPH symptoms, the additional finding of ventriculomegaly on imaging, and confirmatory testing with a trial of CSF drainage, which can predict improvement with CSF shunting. The differential diagnosis must consider common causes of each of the symptoms and include Alzheimer's disease (AD), Parkinson's disease (PD), vascular dementia, and spinal stenosis. Treatment involves CSF diversion, usually through implantation of a shunt from the ventricles to the peritoneal cavity. After surgery and in the absence of other contributing factors, the benefit of surgical intervention can be durable over years.