Normal pressure hydrocephalus

PURPOSE OF REVIEW Since it was first described in 1965, normal pressure hydrocephalus (NPH) has been a controversial subject. New studies have shed light on its epidemiology and pathogenesis and provided objective ways to measure outcome in patients with NPH. Neuroimaging has improved and allows better recognition of both NPH and the presence of overlapping diseases RECENT FINDINGS Several recent epidemiologic studies confirm that NPH is a rare disease, but the presence of large ventricles is a common finding with aging. NPH may be multifactorial, including congenital causes, vascular disease, and impaired CSF absorption. MRI features of NPH include enlarged ventricular size and CSF fluid collection outside the ventricles not due to atrophy. The term disproportionately enlarged subarachnoid space hydrocephalus (DESH) has been used to describe prognostic MRI features in NPH, including a "tight high convexity" and enlargement of CSF spaces in the sylvian fissure. DESH has been included in the Japanese guideline for the diagnosis and treatment of NPH. A new NPH scale has been published that provides an objective framework for evaluating patients with NPH before and after shunt placement. Programmable shunts can noninvasively manage overdrainage complications. Surgical outcome has been improving over time. Recent studies have led to improved recognition of overlapping diseases such as Alzheimer pathology, which co-occurs in about 30% of NPH cases. Fludeoxyglucose positron emission tomography (FDG-PET) is a promising imaging modality for diagnosing NPH and detecting concomitant degenerative disease. SUMMARY A systematic approach to patients with possible NPH allows recognition of the subset of patients who will respond to shunt surgery and identification of those with alternative diagnoses.