血清Na値は正常範囲を示し，振戦せん妄に伴ってcentral pontine myelinolysisを来したアルコール依存症の1症例—MRI所見とその成因について

Central Pontine Myelinolysis (CPM) Following Delirium Tremens in a Case of Alcohol Dependence with Normonatremia: MRI findings and its etiology

　【抄録】　アルコール離脱後，振戦せん妄に伴ってcentral pontine myelinolysis（CPM）が発症したと考えられたアルコール依存症の1症例を報告し，その成因について考察した。これまでCPMは剖検で診断されていたことが多いが，本例は頭部MRIのT₁強調画像で橋底部中央に円形の低信号域，T₂強調画像で同部に高信号域を認め，CPMと診断された。頭部CTでは橋底部に異常所見を認めず，本疾患の診断にMRIは有力な検査法と考えられた。

　現在，CPMの成因として低Na血症の急速補正，ないしは過剰補正が重要視されている。本例の血清Na値は経過中つねに正常範囲を示し，その成因に低Na血症の急速補正，過剰補正を考えることは難しく，アルコール離脱それ自体が発症に関与したことが推測された。また，本例に認められた貧血，肝機能障害，高アンモニア血症，低K血症などが多因子的に関与した可能性も考えられた。

　We reported a case of central pontine myelinolysis (CPM) following delirium tremens in a 46-year-old male with alcoholic dependence.

　Although there have been many reports of CPM, most of them were diagnosed by post-mortem examinations. Our case was diagnosed by magnetic resonance imaging (MRI). T₁-weighted images demonstrated a small, round low signal intensity area in the center of the basis pontis. T₂-weighted images showed a corresponding high signal intensity area. The CT scan revealed only cortical atrophy. We stressed that MRI was valuable for the diagnosis of CPM.

　Hyponatremia, especially its rapid or over-correction is considered as an important etiology of the CPM. However, since normal serum sodium concentration (from 141 to 146 mEq/l; normal range 138-147 mEq/l) was revealed by frequent laboratory examination, our case was not associated with hyponatremia and its rapid or over-correction. Two possible mechanisms were considered as the pathogenesis of CPM in our case : (1) Sudden withdrawal of alcohol intake might have produced the CPM, (2) Multifactorial interrelation between anemia, liver dysfunction, hyperammonemia and/or hypopotassemia might have been the cause of the CPM.