Patients and Methods
We describe four new cases in our own practice and performed a systematic literature search identifying articles that report persistent or sustained visual aura symptoms. Data were obtained from a search in PubMed from their first availability up to March 2014. Search terms included "migraine" OR "visual" in combination with "aura", AND "persistent" OR "sustained." Furthermore, we conducted an additional search with the terms: "visual disturbance", "visual snow" in combination with "persistent" OR "sustained." There were no search limits considering language. This search led to 26 results. We also searched the reference lists of individual articles. Titles and abstracts of all studies retrieved were examined. We included all case descriptions in which criteria for PMA formulated in the International Classification of Headache Disorders, second edition, were met.
For statistical analysis we used chi-square test for normal distributed data and Mann–Whitney U-test for non-normal distributed data. We used SPSS statistical software package 17.0 (IBM Corporation, Armonk, NY, USA).