“The basic facts permit an understanding of the dynamics of cerebrospinal fluid (CSF) circulation and of the various types of hydrocephalus” (Anthony J. Raimondi, 1972).

In 1970s, Raimondi, AJ described the major aspects of hydrocephalus in the CSF dynamics to understand the specificity of various types of hydrocephalus. In our extensive and critical analysis of the previous publications related to the classification/definition of hydrocephalus during the period of 1950 to 2010, the considerable items to characterize the individual type of hydrocephalus were summarized in ten categories, as “Multi-categorical Hydrocephalus Classification (Mc HC)” category I: onset (age, phase), II: cause, III: underlying lesion, IV: symptomatology, V: pathophysiology 1. CSF circulation, VI: pathophysiology 2. ICP dynamics, VII: chronology, VIII: post-shunt, IX: post-endoscopic third ventriculostomy, and X: others (“Multi-categorical Hydrocephalus Classification” by Oi S, 2010). As being described in that publication, the major category to express the characteristic in a single case of hydrocephalus shall be the combination of these categories.

In 2009, I chose to undertake the work of Edior-in-chief, “Journal of Hydrocephalus” (http://wah.kenkyuukai.jp/?l=2), together with an editorial board including the major hydrocephalus researchers worldwide. We have started this work with an exhaustive review of the literature over the past half century, creating a “Hydrocephalus Research World Record Ranking” (HRWRR) as a means of critically analyzing various etiologic, pathogenetic, pathologic, diagnostic, and therapeutic aspects of hydrocephalus in the history of hydrocephalus research. In the critical review of nearly 10,000 publications by the HRWRR committee, it became obvious that the hydrocephalus research has been for a certainty progressing with such numerous research works in that academic road. The “Hydrocephalus Research World Record Ranking 1950–2010” shall indicate the representative hydrocephalus researchers’ personal and worldwide research footsteps in the history.

In this “special issue”, the currently active hydrocephalus researchers worldwide were invited as the author. Each of the authors contributed to delineate the modern concept of the entity, the unique clinical features demonstrated in the most advanced diagnostic procedures, the revolutionary development of the surgical instrumentation/technique, and the outcomes of the treatment in the representative types of hydrocephalus.