[Current State of Diagnosis and Treatment of Idiopathic Normal Pressure Hydrocephalus]

Idiopathic normal pressure hydrocephalus (iNPH) is a common disease with a prevalence of 1 to 3% in the elderly. The Japanese society of normal pressure hydrocephalus has developed clinical guidelines for the management of idiopathic normal pressure hydrocephalus and conducted two multicenter prospective studies for iNPH, which are called SINPHONI and SINPHONI-2. These guidelines define disproportionately enlarged subarachnoid space hydrocephalus (DESH) as iNPH with the specific MRI features of tight high-convexity, the presense of medial subarachnoid spaces and ventriculomegaly. Patients with DESH are known to be highly responsive to shunt surgery. Specifically, 60 to 70% of patients with DESH see improvements in their daily living activities following shunt surgery. While ventriculo-peritoneal shunt surgery (VPS) is most commonly used in western countries, lumbo-peritoneal shunt surgery (LPS) is increasingly used in Japan, as patients with iNPH and their caregivers are more willing to accept lumbar surgery than cranial surgery. LPS does not produce puncture-induced damage to the brain and has been recently confirmed to be effective for the treatment of iNPH. It is important for physicians to consider iNPH while examining patients with dementia, as iNPH is common, treatable, and easy to diagnose using MRI.