Classification

• Primary headache syndromes include migraines with or without aura, the hemicranias and indomethacin-responsive headaches, tension headaches, chronic daily headaches, and cluster headaches.
• Secondary headaches have specific etiologies, and symptomatic features vary depending on the underlying pathology (e.g., SAH, tumor, hypertension, posterior reversible encephalopathy syndrome, reversible cerebral vasoconstriction syndrome (RCVS), analgesic overuse, iatrogenic).
• Migraine without aura: At least five attacks that last 4–72 hours. Symptoms should include at least two of the following: unilateral location, pulsating or throbbing, moderate to severe in intensity, aggravated by activity, and at least one of these associated features: nausea/vomiting, photophobia, and/or phonophobia.
• Migraine with aura: Same as above, except at least two attacks with an associated aura that lasts from 4 minutes to 1 hour (longer than 60 minutes is a red flag). The aura should have a gradual onset, should be fully reversible, and can occur before, with, or after headache onset.
• Cluster headache: Unilateral orbital or temporal pain with lacrimation, conjunctival injection, nasal congestion, rhinorrhea, facial swelling, miosis, ptosis, and eyelid edema.
• Rebound headache (medication overuse headache) occurs in the setting of chronic use of analgesics or narcotics.
• Trigeminal neuralgia presents as episodic sharp stabbing pain that is unilateral. Rule out MS or an alternative etiology with MRI.
• Temporal arteritis presents as a dull unilateral headache with a thick tortuous artery over temporal region. The disease is almost exclusively limited to individuals older than 60 years with jaw claudication, low-grade fever, and an elevated ESR and CRP.

Etiology

Secondary headache etiologies include:

• Subdural hematoma (SDH), intracerebral hemorrhage, SAH, AVM, brain abscess, meningitis, encephalitis, vasculitis, obstructive hydrocephalus, and cerebral ischemia or infarction.
• Idiopathic intracranial hypertension (commonly known as pseudotumor cerebri) presents with headache, papilledema, diplopia, and elevated CSF pressure (at least >20 cm H₂O in relaxed lateral decubitus position). CVST should be ruled out in all patients presenting with suspected idiopathic intracranial hypertension.
• Extracranial causes include giant cell arteritis, sinusitis, glaucoma, optic neuritis, dental disease (including temporomandibular joint syndrome), and disorders of the cervical spine (i.e., “cervicogenic” headache).
• Systemic causes include fever, viremia, hypoxia, carbon monoxide poisoning, hypercapnia, systemic hypertension, allergy, anemia, caffeine withdrawal, and vasoactive or toxic chemicals (e.g., nitrites).
• Depression is a common cause of long-standing, treatment-resistant headaches. Specific inquiry about vegetative signs of depression and exclusion of other causes help support this diagnosis.