Trigeminal autonomic cephalalgias.

The trigeminal autonomic cephalalgias (TACs) are a group of primary headache syndromes all marked by headache and associated autonomic features. The TACs include cluster headache, paroxysmal hemicrania, hemicrania continua, and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing syndrome. Diagnosis is made after looking at headache frequency, duration, and accompanying symptoms. Each TAC has its own unique treatment modality, which is discussed in depth.