髄液の産生・吸収に関する最新の知見—100年にわたる教義的学説の再考と改訂

New Findings and Concepts on Production and Absorption of Cerebrospinal Fluid: Reconsiderations and Revisions of an Unquestioningly Accepted Dogma of 100 Years

脳脊髄液生理学の教義となっているbulk flow説「脳脊髄液は脈絡叢で産生され一方向に流れて，頭頂部のくも膜顆粒から吸収される」の誤謬が近年指摘されており，その再考が必要である。脳脊髄液と脳間質液には自由な水交換があり，一括して脳細胞外液と捉えるべきである。本稿では，脳細胞外液の産生・吸収に関して，従来の仮説の問題点と新しい考え方（毛細血管説，脳リンパ排液経路，脳脊髄液は循環しない）を概説する。

Abstract

It has been recently pointed out that there are fallacies in the bulk flow theory, a dogmatic idea of cerebrospinal fluid (CSF) physiology, which assumes that CSF is produced by the choroid plexus and circulates unidirectionally from the ventricles to the subarachnoid space to be absorbed by the arachnoid villi in the parietal region. Therefore, CSF physiology now needs to be reconsidered. Since there is free exchange of water between the CSF and the brain interstitial fluid (ISF), when considering the dynamics of water in the brain, we should regard these two fluid compartments collectively as brain extracellular fluid. In this review, I discuss the contentious issues in the traditional theory of CSF physiology, and then introduce new understandings of the production and absorption of the brain extracellular fluid, such as the capillary theory asserting that brain ISF is produced and absorbed mainly at the cerebral capillaries, the brain lymphatic drainage pathway, and the non-existence of unidirectional CSF circulation.