1 Headache Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, USA.
Brain. 2014 May;137(Pt 5):1419-28. doi: 10.1093/brain/awu050. Epub 2014 Mar 18.
Patients with 'visual snow' report continuous tiny dots in the entire visual field similar to the noise of an analogue television. As they frequently have migraine as a comorbidity with ophthalmological, neurological and radiological studies being normal, they are offered various diagnoses, including persistent migraine aura, post-hallucinogen flashback, or psychogenic disorder. Our aim was to study patients with 'visual snow' to characterize the phenotype. A three-step approach was followed: (i) a chart review of patients referred to us identified 22 patients with 'visual snow'. Fifteen had additional visual symptoms, and 20 patients had comorbid migraine, five with aura; (ii) to identify systematically additional visual symptoms, an internet survey (n = 275) of self-assessed 'visual snow' subjects done by Eye On Vision Foundation was analysed. In two random samples from 235 complete data sets, the same eight additional visual symptoms were present in >33% of patients: palinopsia (trailing and afterimages), entoptic phenomena (floaters, blue field entoptic phenomenon, spontaneous photopsia, self-light of the eye), photophobia, and nyctalopia (impaired night vision); and (iii) a prospective semi-structured telephone interview in a further 142 patients identified 78 (41 female) with confirmed 'visual snow' and normal ophthalmological exams. Of these, 72 had at least three of the additional visual symptoms from step (ii). One-quarter of patients had 'visual snow' as long as they could remember, whereas for the others the mean age of onset was 21 ± 9 years. Thirty-two patients had constant visual symptoms, whereas the remainder experienced either progressive or stepwise worsening. Headache was the most frequent symptom associated with the beginning or a worsening of the visual disturbance (36%), whereas migraine aura (seven patients) and consumption of illicit drugs (five, no hallucinogens) were rare. Migraine (59%), migraine with aura (27%), anxiety and depression were common comorbidities over time. Eight patients had first degree relatives with visual snow. Clinical investigations were not contributory. Only a few treatment trials have been successful in individual patients. Our data suggest that 'visual snow' is a unique visual disturbance clinically distinct from migraine aura that can be disabling for patients. Migraine is a common concomitant although standard migraine treatments are often unhelpful. 'Visual snow' should be considered a distinct disorder and systematic studies of its clinical features, biology and treatment responses need to be commenced to begin to understand what has been an almost completely ignored problem.
患者出现“视觉雪”现象时，会报告称整个视野中出现连续的微小光点，类似于模拟电视的雪花噪声。由于他们经常伴有偏头痛，且眼科、神经科和放射科检查均正常，因此会被诊断出各种疾病，包括持续性偏头痛先兆、幻觉后闪光或心因性障碍等。我们旨在研究“视觉雪”患者，以明确其表型特征。为此，我们采用了三步法：（i）对转诊至我们处的患者进行病历回顾，共发现 22 例“视觉雪”患者。其中 15 例伴有其他视觉症状，20 例伴有偏头痛，其中 5 例伴有先兆；（ii）为了系统地识别其他视觉症状，我们对 Eye On Vision Foundation 进行的、由自我评估“视觉雪”患者参与的互联网调查（n=275）进行了分析。在 235 个完整数据集的两个随机样本中，同样的 8 种附加视觉症状在>33%的患者中存在：后像（拖尾和余像）、内视现象（飞蚊症、蓝点内视现象、自发性闪光、眼内自发光）、畏光和夜视障碍（夜间视力受损）；（iii）对进一步的 142 例患者进行前瞻性半结构式电话访谈，确定了 78 例（41 例为女性）经证实的“视觉雪”患者和正常的眼科检查结果。其中，72 例至少有 8 种附加视觉症状中的 3 种。四分之一的患者从记忆开始就出现“视觉雪”现象，而对于其余患者，发病的平均年龄为 21±9 岁。32 例患者的视觉症状持续存在，而其余患者的症状表现为逐渐恶化或阶段性恶化。头痛是与视觉障碍开始或恶化最相关的症状（36%），而偏头痛先兆（7 例）和非法药物滥用（5 例，无致幻剂）较为罕见。偏头痛（59%）、偏头痛先兆（27%）、焦虑和抑郁是随时间推移的常见共病。8 例患者有一级亲属患有“视觉雪”。临床检查结果无明显异常。仅有少数针对个别患者的治疗试验取得了成功。我们的数据表明，“视觉雪”是一种独特的视觉障碍，在临床上与偏头痛先兆不同，可能会使患者丧失能力。偏头痛很常见，但标准的偏头痛治疗往往无效。“视觉雪”应被视为一种独特的疾病，需要对其临床特征、生物学和治疗反应进行系统研究，以开始了解这一几乎完全被忽视的问题。
