Duane症候群Ⅲ型のMRI所見

Magnetic resonance imaging findings in Duane's retraction syndrome typeⅢ

要約　目的：40歳の女性で幼少時から左眼外斜視と眼球運動障害を自覚し，Duane症候群Ⅲ型と診断された症例のMRI所見の報告。症例と経過：家族歴はなく，両眼とも視力は1.2で眼底にも異常は認めなかった。脳幹部MRI T2-強調の斜軸像で患側の外転神経の欠損を橋レベルで認めたが，動眼神経については両側とも確認できた。眼窩MRI T1-強調の矢状断画像で患側眼窩後方の左眼外直筋筋腹が上下に2つに分離する所見を認めた。この所見を支持するように冠状断画像でも眼窩後方での外直筋の分離を認めた。結論：外直筋の2分離所見は，Duane症候群における異常神経支配が関係していると推察される。

Abstract.　Purpose：Magnetic resonance imaging（MRI）was used to demonstrate extraocular muscles（EOMs）and associated motor nerves in Duane's retraction syndrome type Ⅲ in a 40-year-old woman with longstanding strabismus and abnormal eye movement in left eye. Case and Course：The patient had no family history of ophthalmic problems. Visual acuity was 1.2OU with correction. Fundus examination showed no abnormalities. Heavily T2-weighted axial images at the level of the pons, the left abducens nerve was not demonstrated, but the oculomotor nerves were identified. Structural abnormalities of the left lateral rectus（LR）muscle included splitting of the left LR belly into superior and inferior portions on quasi-sagittal T1-weighted MRI. Consistent with this finding, quasi-coronal MRI planes of the left orbit demonstrated that the LR muscle became bifid in the deep orbit. Conclusion：These findings suggest that dysinnervation is atrophic factor in the deep bellies of LR muscle in Duane retraction syndrome.