Cluster headaches and other trigeminal autonomic cephalgias (TAC)

Cluster headaches are a type of nervous system disorder that causes severe, short-lived, but extremely painful headaches that happen in groups or 'clusters.' These episodes can last for weeks or months, followed by long periods of being pain-free.

The condition specifically involves the trigeminal nerve, a large nerve pathway that carries sensation from your face to your brain. When these headaches occur, the body's autonomic nervous system—which controls automatic functions like heart rate and sweating—becomes overactive, leading to physical changes on one side of the face.

While the exact trigger is still being studied, scientists believe the issue starts in the hypothalamus, the part of the brain that acts as your internal clock. Because this area regulates sleep and daily rhythms, it explains why these attacks often happen at the exact same time every day.