{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://openvisual.org/schema/migraine-aura/1.0",
  "title": "OVS: Migraine Aura",
  "description": "Visual disturbance caused by cortical spreading depression. Produces scotoma or fortification spectrum (zig-zag expanding crescent).",
  "allOf": [
    { "$ref": "https://openvisual.org/schema/symptom-base/1.0" },
    {
      "type": "object",
      "required": ["subtype"],
      "properties": {
        "ovs_type":     { "const": "ovs:migraine-aura" },
        "subtype":      { "type": "string", "enum": ["scotoma", "fortification"], "description": "scotoma: dark/blind central area. fortification: expanding zig-zag luminous arc (Cortical Spreading Depression)." },
        "duration_sec": { "type": "number", "minimum": 0, "description": "Typical episode duration in seconds" }
      }
    }
  ]
}