Study on the Use of Visual Evoked Potentials for Early Diagnosis of Subclinical Visual System Impairment

对49例疑似视神经病变患者和28例正常成人进行了持续30分钟的单眼模式逆转刺激。监测每只眼P100的峰值潜伏期为30分钟。在正常对照中，p100潜伏期保持正常（低于118mce） 30分钟。患者组结果分为三类；1)正常，2)1型异常，3)2型异常。只有当P100延迟保持正常（低于118 msec） 30分钟时，结果才被认为是“正常”。当P100潜伏期最初正常，但至少有一个后续反应延迟（超过118 msec）或不存在时，结果称为“1型异常”。当最初的反应已经延迟或缺失时，结果被称为“2型异常”。在传统的模式反转刺激方法中，只有2型异常的情况才会被检测到。我们的研究结果表明，这种新方案提高了视神经病理检测的能力。与提高的检出率相对应的分数似乎以1型异常的眼睛为代表。采用这种新的检测方法，视神经亚临床病变的检出率从29%上升到48%，而传统的方法是测量100-150求和得到的一个或两个诱发电位。22例多发性硬化患者中，21例（96%）表现为1型或2型异常。在12例眼科检查无异常的多发性硬化患者中，9例（75%）显示1型或2型异常。我们的新方案持续刺激30分钟是非常有用的检测亚临床视神经病变。

A new protocol of continuous monocular pattern reversal stimulation for 30 min was applied to 49 patients with suspected optic nerve pathology and 28 normal adults. A peak latency of P100 in each eye was monitored for 30 min. In normal controls, p100 latency remained normal (below 118 msce) for 30 min. Results in the patient group were divided into three categories; 1) Normal, 2) Type 1 abnormality, and 3) Type 2 abnormality. Only when P100 latency remained normal (below 118 msec) for 30 min, the result was regarded as "normal". When P100 latency was initially normal and at least one of subsequent responses was delayed (longer than 118 msec) or absent, the result was called "type 1 abnormality". When an initial response was already delayed or absent, the result was called "type 2 abnormality". In a conventional method of pattern reversal stimulation, only cases of type 2 abnormality are detected. Our results revealed that this new protocol increases capability of detecting optic nerve pathology. The fraction corresponding to the improved detection rate seemed to be represented by eyes with type 1 abnormality. By using this new testing method, the detection of subclinical lesions of the optic nerve rise from 29 % to 48 %, compared to that of the conventional method which is measurement of one or two evoked potentials obtained by 100-150 summations. In 22 patients with multiple sclerosis, 21 patients (96%) showed either type 1 or type 2 abnormality. In 12 patients with multiple sclerosis without abnormality on ophthalmologic examination, 9 cases (75 %) showed either type 1 or type 2 abnormality. Our new protocol of continuous stimulation for 30 min is very useful for detecting subclinical optic nerve lesions.