Headache is one of the most common medical complaints encountered in ambulatory care and emergency departments worldwide. When evaluating a patient presenting with acute or recurrent head pain, clinicians must first distinguish between primary headache disorders—where the headache itself is the underlying condition—and secondary headache disorders, which stem from underlying systemic or structural pathology.
Epidemiological data reveals clear distribution patterns among primary headache types in clinical practice:
Tension-Type Headache: Represents the most prevalent primary headache disorder, accounting for approximately 69% of primary headache presentations.
Migraine: Comprises approximately 16% of primary headache cases, characterized by episodic, pulsating pain often accompanied by photophobia, phonophobia, and nausea.
Idiopathic Stabbing Headache: Accounts for approximately 2% of presentations.
Exertional Headache: Represents roughly 1% of primary cases.
Cluster Headache: Represents a rare primary entity, accounting for roughly 0.1% of the overall headache population.
Conversely, secondary headaches arise from identifiable underlying organic pathologies. Common causes include systemic infections, which account for up to 63% of secondary headache presentations. Head injuries contribute approximately 4%. Vascular disorders represent about 1%. Subarachnoid hemorrhage—a critical medical emergency—accounts for less than 1%. Brain tumors or intracranial space-occupying lesions represent roughly 0.1% of secondary presentations.
Differentiating between primary TACs and secondary conditions requires careful clinical screening. Because TACs feature prominent cranial autonomic signs, clinicians must rule out secondary structural lesions located in the anterior fossa, parasellar region, or cavernous sinus that can mimic primary TAC presentations. Red flag symptoms—such as late age of onset, sudden onset "thunderclap" presentation, focal neurological deficits, papilledema, or underlying systemic illness—warrant immediate diagnostic neuroimaging to rule out life-threatening secondary causes prior to establishing a primary diagnosis.