Glucocorticoid投与により著明に改善したcentral pontine myelinolysisの1例

A Case of Central Pontine Myelinolysis with Neurological Recovery after Administration of Glucocorticoid

　Central pontine myelinolysis（CPM）は低Na血症の急速な補正後に橋底部などに脱髄をきたす疾患で，未だ適切な治療法がなく，動物モデルで予防効果のあるglucocorticoid（GC）も臨床では否定的見解が多い。最近，頭部外傷例でGCの投与により機能回復したCPMの1例を経験したので報告する。症例は65歳の男性で，入院時に低Na血症［122 mEq／l］が指摘された。受傷2時間後に傾眠になり，右前頭葉血腫を除去して，GC投与下にNaを補充したところ意識が回復した。しかし，2日後に昏睡と四肢麻痺になり，CTで著変はなかったが，臨床経過および神経症状から，CPMと診断された。血清Na値を115から125 mEq／lに維持してGCを継続すると，2週目より神経症状が改善され，8カ月後には日常生活で介助を要しなくなった。MRIで橋底部にT1WIで低信号，T 2 WIで高信号の5mm径の病変が描出された。文献的に報告されているMRIで診断されたCPMの22生存例を検討したが，CPMは必ずしも不可逆的病態とは言えず，自験例ではCPMの初期におけるGCの臨床効果が示唆された。

A survival case of central pontine myelinolysis (CPM) is reported herein with a review of 22 MRI -analyzed CPM survivors in the literature.

A 65-year-old male was struck on the forehead while in a traffic accident. He was almost fully conscious and neurologically free on admission. Laboratory data were normal except hyponatremia [122mEq/l] and hypoproteinemia [5.8g/dl]. 2 hours later he became drowsy and left hemiparesis.The CT scan showed right frontal cerebral hema-toma leading to a remarkable midline shift. Imme-diately, aspiration of the hematoma was performed. On the next day, he returned to the initial neur-ological level. On the third day, however, he again became comatose followed by tetraparesis and ataxic respiration. While the CT scan at that time did not display any abnormality in the pons, the severe dysfunction of the brain stem occurred after the correction of hyponatremia strongly suggesting CPM. The serum Na levels were kept between 110 and 125 [mEq/l]. In addition, 375 mg of methyl-prednisolone had been daily administrated during and after a gradual correction of the hyponatremia, because glucocorticoid proved to be effective in the models of CPM. The neurological condition began to improve on the 14th day after admission. Eventu-ally, he became conscious and independent in his daily activities, the time span being 8 months after the trauma. The trident MRI lesion in the basis pontis was 5 mm in diameter and much smaller than clinically expected.

The 23 MRI-analyzed CPM survivors were revi-ewed in the literature including the present case. There were 7 males and 16 females, with a mean age of 48.5 years. In all but 2 cases, hyponatremia preceded the onset of CPM. Among the 18 cases described neurologically in detail, 15 cases im-proved including 5 cases showing almost full recov-ery.

On the other hand, MRI is more sensitive to detect the CPM lesion than CT scan. The lesion size on MRI was rather diverse, probably because the inter-val between the onset of CPM and the date of MRI was different among the cases. Limited to acute stage, however, the alternations in the lesion on MRI were reported to correlate with the neur-ological conditions.

This clinical study suggests that the nature of CPM lesion is not always irreversible, especially at its initial phase. Glucocorticoid proved to be useful in improving the neurological outcome in our case.