乳児視覚障害のVEPによる視覚系発達過程の検討—重度精神運動発達遅延を伴う症例

Course of VEP during visual development in infants with severe mental retardation

　重度の精神運動発達遅延を伴い，視反応が認められない乳児（明らかな眼病変を伴う症例は除外）の視反応出現の判定は少なくとも2歳までの経過観察が必要であり，後頭部視中枢での障害の程度および発達のモニターにVEPは有用と考えられた．2歳を過ぎてもVEPが認められない場合は視反応出現は期待できないのではないかと考えられた．2歳以前にVEPが記録された症例では，VEP上の発達過程において網膜皮質路は最終的にはほぼ正常の発達を示した．さらに，高振幅でかつ多相性の波形が認められれば少なくとも後頭部視中枢での処理反応の発達が期待でき，全身的な精神運動発達遅延が改善されれば視機能の発達が期待できる．しかし，VEPが低振幅のままでかつ持続時間の長いN70およびP100成分のみの場合は，後頭部視中枢でいわゆる反応が停滞していることが考えられ，たとえ精神運動発達遅延が改善しても必ずしも視反応の出現は期待できないか，または出現しても良好な視反応の発達は期待できないと考えられた．

We observed 8 infants with suspected cerebral blindness and documented the course of visual development by means of visual evoked potential (VEP) over an average of 6-year period. The mental retardation was caused by hydrocephalus 2 cases, cerebral hemorrhage 2, acute encephalitis 1, Reye syndrome 1, and cerebral palsy 1.

Signs of visual recovery appeared in 4 cases about 2 years after the initial episode. The course of visual recovery was usually very slow and paral-leled that of improvements in mental retardation. The other 4 infants showed noobvious visual response in spite of recovery in the state of mental retardation. Two of the infants showed no detectable VEP. In the other two, we observed improvements in VEP responses, which were characterized by very low amplitude in earlier components and absence of later components. The recovery of mental retardation in the former group with apparent visual response was better than in the latter with no visual response. In visu-ally disturbed infants, visual development can be expected in cases with VEP responses with higher amplitude and multiphased wave form, provided that the mental retardation starts to recover within 2 years after the original episode.

Rinsho Ganka (Jpn J Clin Ophthalmol) 42(6) : 671-674, 1988