低ナトリウム血症の急速補正後に発症したcentral pontine and extrapontine myelinolysisの1剖検例

CENTRAL PONTINE AND EXTRAPONTINE MYELINOLYSIS FOLLOWING RAPID CORRECTlON OF HYPONATREMIA:REP0RT OF AN AUTOPSY CASE

　抄録　低ナトリウム血症の短期間の急激な補正後に昏睡と弛緩性四肢麻痺を呈し，central pontine myeli—nolysis （以下CPM）と診断し，剖検にて確認し得た1症例を経験した。症例は61歳，女性。23年前に頭蓋咽頭腫の手術，15年後には同腫瘍再発のため。再手術を受け，以後corticosteroidおよびclofibrate投与を受けていた。尿路感染を契機に副腎不全状態の増悪と低ナトリウム血症をきたし，2日問で血清ナトリウム値は117mEq／lから161mEq／lに急速に補正された。その結果，昏睡と弛緩性四肢麻痺をきたし当科に紹介入院。この間低血圧，低血糖，呼吸不全および肝不全はいずれも認められず，低ナトリウム血症とその急速な補正が意識障害および四肢麻痺の原因と考えられた。剖検にて橋のみならず，大脳，中脳，小脳にも左右対称性の広範な脱髄性病変が確認された。本症例はNorenbergらの指摘するごとく低ナトリウム血症の急速な補正の危険性を示唆する臨床的に注目すべき医原性病態の症例であるとして，文献的検索を加え報告した。

A case of central pontine myelinolysis (CPM) following rapid correction of hyponatremia was reported and literatures were reviewed. The case was 61-year-old nonalcoholic female who had taken an operation of craniopharyngioma 23 years ago. Fifteen years later, she received re-operation for the recurrent tumor, followed by replacement therapy of corticosteroid and clofibrate. She was otherwise well until two weeks before entry, when she noticed abrupt onset of high grade fever, nausea, vomiting and general malaise. She was admitted to an emergency hospital because of weakness, disorientation and a slight impairment of consciousness, but she was able to speak and to take some food per os.

Laboratory studies disclosed urinary tract infec-tion and showed a serum sodium level of 117 mEq/l, pottasium 2.9mEq/l, a serum osmorality 232mO sm/l and urine osmorality 141 mEq/l. She was diagnosed to have an exacerbation of adrenal insufficiency with hyponatremia and hypotonie dehydration triggered by urinary tract infection. Intravenous administration of vitamine B complex, electrolytes including KCL, 5% glucose solution and physiological saline with a large amount of corticosteroid was performed aggresively. Serum sodium concentration was raised to 161 mEq// in two days, and the increased level had been main-tained more than five days, resulting in coma and flaccid quadriplegia. During this period, there was no episode of hypotension, hypoglycemia, hypoxia nor hepatic failure which could have caused brain damage. She was then transferred to our hospital, and nasal tubing nutrition and/or total parenteral alimentation was performed to maintain the balan-ce of electrolytes. After elapsing the acute phase of the neurological disturbance, she remained in a vegetative state and quadriplegia, and died of emaciation six months later.

The autopsy disclosed wide ranged demylinated lesions bilaterally and symmetrically not only in the pons but in the cerebrum, midbrain and cereb-ellum. CT scans were performed four times, which revealed only isodensity mass with partial calcification in the pitritary fossa and suprasellar area. The autopsy proven demyelinated lesions were not detected by CT scans.

This case suggested that CPM might have been caused by a rapid and sustained rise in serum sodium from a hyponatremic baseline, as Noren-berg et al. has emphasized.