Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus (Third Edition): Endorsed by the Japanese Society of Normal Pressure Hydrocephalus

Abstract

Among the various disorders that manifest with gait disturbance, cognitive impairment, and urinary incontinence in the elderly population, idiopathic normal pressure hydrocephalus (iNPH) is becoming of great importance. The first edition of these guidelines for management of iNPH was published in 2004, and the second edition in 2012, to provide a series of timely, evidence-based recommendations related to iNPH. Since the last edition, clinical awareness of iNPH has risen dramatically, and clinical and basic research efforts on iNPH have increased significantly. This third edition of the guidelines was made to share these ideas with the international community and to promote international research on iNPH. The revision of the guidelines was undertaken by a multidisciplinary expert working group of the Japanese Society of Normal Pressure Hydrocephalus in conjunction with the Japanese Ministry of Health, Labour and Welfare research project. This revision proposes a new classification for NPH. The category of iNPH is clearly distinguished from NPH with congenital/developmental and acquired etiologies. Additionally, the essential role of disproportionately enlarged subarachnoid-space hydrocephalus (DESH) in the imaging diagnosis and decision for further management of iNPH is discussed in this edition. We created an algorithm for diagnosis and decision for shunt management. Diagnosis by biomarkers that distinguish prognosis has been also initiated. Therefore, diagnosis and treatment of iNPH have entered a new phase. We hope that this third edition of the guidelines will help patients, their families, and healthcare professionals involved in treating iNPH.

Keywords: clinical guideline; diagnosis; idiopathic normal pressure hydrocephalus; management; treatment.

Fig. 1

DESH. Typical MRI of a patient with iNPH. Narrowing of the CSF spaces near the vertex and widening of the Sylvian fissure are good indicators that iNPH will respond to treatment. The few wide sulci that are seen on the cerebral convexity (white arrow) are all in the vicinity of large, superficial arteries. DESH: disproportionately enlarged subarachnoidspace hydrocephalus, MRI: magnetic resonance imaging, CSF: cerebrospinal fluid, iNPH: idiopathic normal pressure hydrocephalus.

Fig. 2

Classification of hydrocephalus in Relation to iNPH. DESH: disproportionately enlarged subarachnoid-space hydrocephalus.

Fig. 3

Idiopathic normal pressure hydrocephalus: algorithm of diagnosis and management.

Fig. 4

Callosal angle. (A) The callosal angle, which is the angle between the left and right parts of the corpus callosum (superior walls of ventricles) should be measured on the coronal plane, (B) on a slice through the posterior commissure and perpendicular to the anterior commissure–posterior commissure line.

Fig. 5

z-EI and BVR. Evaluation of the z-EI and BVRs should be done on the coronal plane, (A) on a slice through the anterior commissure and perpendicular to the AC-PC line (green). (B) The height of the frontal horns of the lateral ventricles (yellow line) in the z-axis divided by the midline diameter of the skull (magenta line) is defined as the z-EI, with a cutoff value of 0.42. The BVR at the AC levels are measured as the maximum z-axial length of the brain just above the lateral ventricles (yellow line) divided by the maximum length of the lateral ventricles (cyan line). When the coronary plane is through the AC, the value will be below 1.0, and when the plane is through the PC, it is below 1.5. This figure shows z-EI = 46.7/95.0 = 0.49 >0.42, BVR at the AC level = 28.1/46.7 = 0.6 <1.0. AC-PC: anterior commissure–posterior commissure, BVR: brain/ventricle ratio, z-EI: z-Evans index.