Cluster headache

Nervous system and special senses

Adverse effects of drugs on the nervous system

Global cerebral dysfunction

Metabolic disorders

Neurologic pain syndromes

Summary

Cluster headache is a type of headache that is extremely painful and occurs in clusters. They usually affect one side of the head, typically around one eye. Some people experience a "cluster period" of several weeks or months where they get multiple cluster headaches daily, while others only experience a cluster period once every few years.