急性視神経炎における造影MRI所見と疼痛および視力予後の関連

Contrast-enhanced MRI findings as related to pain and visual outcome in acute optic neuritis

要約　目的：広義の急性視神経炎での，MRI所見と，疼痛と視力転帰との関連の報告。

対象と方法：過去8年間に急性視神経炎で初診し，診療録に十分な記録のある29例を対象とした。男性5例，女性24例で，平均年齢は44歳である。16例が特発性，8例が多発性硬化症，5例が視神経脊髄炎またはその関連疾患であった。全例にガドリニウム造影による冠状断のMRIを行い，病巣の局在と長さを評価した。視力はlogMARとして評価した。

所見と経過：病巣の部位は，眼窩内が23例，眼窩外が6例であった。疼痛は20例にあり，そのすべてが眼窩内に病巣があった。眼窩外に病巣がある6例には疼痛がなかった（p＜0.001）。疼痛がある症例は，病巣の範囲が有意に長かった。病巣の長さは治療前後の視力と有意に相関した。病巣長が20mmを超えると，治療後の視力が不良であった。

結論：広義の急性視神経炎に対し，造影MRIにより病巣の局在と長さを検索した。病巣が眼窩内にある症例では疼痛が有意に多く，病巣長が大きいと治療前後の視力が不良であった。

Abstract　Purpose: To report contrast-enhanced MRI findings in acute optic neuritis as related to pain and visual outcome.

Cases and Method: This retrospective study was made on 29 cases of acute optic neuritis who were treated by us in the past 8 years. The series comprised 5 males and 24 females. The age averaged 44 years. Sixteen cases were diagnosed with idiopathic optic neuritis, 8 cases with multiple sclerosis, and 5 cases with neuromyelitis optica. All the cases were evaluated by contrast-enhanced MRI to identify the location of the lesion and its anteroposterior extent. Visual acuity was evaluated in terms of logMAR.

Findings and Clinical Course: The causative lesion was located in the orbit in 23 cases and out of the orbit in 6 cases. Pain was present in 20 cases and all had causative lesion in the orbit. Six cases who felt no pain had causative lesion out of the orbit. The difference was significant（p＜0.001）. Extent of the lesion along the optic nerve was significantly related with visual acuity before or after treatment. Visual outcome was poor when the lesion extended for 20 mm or over.

Conclusion: Cases of acute optic neuritis showed significantly more frequent pain when the lesion was located in the orbit. Cases with extensive lesion showed poor visual outcome.