A type of migraine occurring in clusters – that is, a patient may have an attack daily for several days and then none for weeks or months. The pain is on one side of the head, often centred over the eye. The pain is excruciatingly severe and often associated with tears, nasal discharge and production of thick saliva from the same side of the mouth. It is treated either with drugs such as SUMATRIPTAN or with breathing 100 per cent oxygen.