Apkarian P, Bour L J, Barth P G, Wenniger-Prick L, Verbeeten B
Department of Physiology I, Medical Faculty, Erasmus University, Rotterdam, The Netherlands.
Brain. 1995 Oct;118 ( Pt 5):1195-216. doi: 10.1093/brain/118.5.1195.
We report a newly identified syndrome in which nasal retinal fibres fail to decussate due to the inborn absence of an optic chiasm. Visual evoked potential (VEP) assessment and neuro-opththalmic evaluation in two unrelated, non-albino children revealed the unusual visual pathway anomaly in the form of misrouted retinal-fugal projections. Monocular VEP responses across the occiput, regardless of stimulus mode (full- or partial-field pattern onset, pattern reversal, luminance flash or high temporal frequency luminance flicker) showed unequivocal evidence of pathological VEP ipsilateral asymmetry. Marked attenuation of primary visual evoked responses from the occiput contralateral to the eye of stimulation, indicative of aberrant contralateral retinal-fugal projections, was confirmed by MRI which depicted the remarkable achiasmatic condition. MRIs and neurological evaluation also confirmed the absence of accompanying congenital or acquired brain malformations or anomalies. Ophthalmic evaluation revealed that both achiasmatic children had reduced distance acuity for age, alternating esotropia, torticollis, head tremor and ocular motor instability; visual fields were normal. Eye movements were also monitored and indicated congenital nystagmus waveforms in the horizontal plane; see-saw nystagmus was observed in the the horizontal plane; see-saw nystagmus was observed in the vertical and torsional planes. The age range of the two children during evaluation and follow-up, over a 6-year period, was about 4-15 years. Comparisons of VEP responses from age-matched normal, albino and idiopathic congenital nystagmus controls, recorded under the same VEP test conditions, were also performed. In contrast to the achiasmatic ipsilateral inter-ocular asymmetry, the albinos showed the expected monocular VEP topography pattern of contralateral asymmetry. Also as expected, VEP profiles from the normal controls and those with congenital nystagmus, evinced no aberrant asymmetry patterns. In general, the results indicate that the VEP misrouting protocol is indispensable for the non-invasive electrophysiological detection and differential diagnosis of optic pathway mutations and may well identify individuals with purported idiopathic congenital nystagmus or albinism that are, in fact, achiasmatic.
我们报告了一种新发现的综合征，其中由于先天性缺乏视交叉，鼻侧视网膜纤维无法交叉。对两名无亲缘关系的非白化病儿童进行视觉诱发电位（VEP）评估和神经眼科检查，发现了视网膜-视束投射路径异常这种不寻常的视觉通路异常。无论刺激模式如何（全视野或半视野模式起始、模式反转、亮度闪光或高时间频率亮度闪烁），枕部的单眼VEP反应均显示出病理性VEP同侧不对称的明确证据。MRI证实了刺激眼对侧枕部的初级视觉诱发电反应明显减弱，这表明对侧视网膜-视束投射异常，MRI显示出明显的无交叉视路情况。MRI和神经学评估还证实没有伴随的先天性或后天性脑畸形或异常。眼科检查显示，两名无交叉视路的儿童年龄相关的远视力下降、交替性内斜视、斜颈、头部震颤和眼球运动不稳定；视野正常。还对眼球运动进行了监测，发现水平面上有先天性眼球震颤波形；在垂直和扭转平面上观察到了跷跷板样眼球震颤。在6年的评估和随访期间，两名儿童的年龄范围约为4至15岁。还在相同的VEP测试条件下，对年龄匹配的正常、白化病和特发性先天性眼球震颤对照的VEP反应进行了比较。与无交叉视路的同侧眼间不对称不同，白化病患者显示出预期的对侧不对称单眼VEP地形图模式。同样如预期的那样，正常对照和先天性眼球震颤患者的VEP图谱没有异常不对称模式。总体而言，结果表明VEP路径异常检测方案对于视路突变的非侵入性电生理检测和鉴别诊断必不可少，并且很可能识别出实际上是无交叉视路的所谓特发性先天性眼球震颤或白化病患者。
