特発性正常圧水頭症の神経病理と最近の動向

Neuropathology of Idiopathic Normal Pressure Hydrocephalus: A Study of Three Autopsy Cases and a Literature Review

特発性正常圧水頭症に特異的な神経病理所見は確立されていない。剖検脳では血管壁の硬化性変化や脳実質の虚血性変化が高頻度に認められることが報告されており，臨床病理学的にビンスワンガー病との異同が議論されている。生検脳組織ではアルツハイマー病の病理所見が年齢調整した一般人口における頻度と同程度に認められることやアクアポリン4の発現変化が報告されており，後者は髄液循環動態の異常に関連する現象と考えられる。

Abstract

We present neuropathological findings in three autopsy brains from patients diagnosed clinically with idiopathic normal pressure hydrocephalus (iNPH) in Japan; still, specific findings of iNPH remain unclear. Comorbid atherosclerosis and hypertensive microvascular diseases, including arterio- and arteriolosclerosis and ischemic changes in the brain parenchyma, are frequently (65%) observed in autopsy brain tissue from patients with iNPH, which has drawn attention to the clinicopathological similarities and differences between iNPH and Binswanger's disease. Additionally, Aβ protein deposition and phosphorylated tau-positive neurofibrillary tangles and neuropil threads are observed in cerebral cortical biopsy specimens obtained during intracranial pressure monitoring or shunt surgery among a subset of patients with iNPH. These findings are as frequent as those reported in autopsy data of the age-matched general population. Alterations in aquaporin-4 expression in the cerebral cortex have also been reported, suggestive of a possible association with altered volume or composition of the interstitial fluid in the microenvironment, particularly in the vicinity of capillaries, or glymphatic system dysfunction and consequent altered interstitial fluid drainage. Greater understanding of the normal anatomical structures and pathways involved in cerebrospinal fluid circulation, particularly in absorption and drainage, in the craniospinal region is essential for better clarity regarding iNPH neuropathology.