Condition	Characteristics
Acute glaucoma	Associated with blurred vision, nausea, vomiting, and seeing halos around lights; ophthalmologic emergency
Acute or chronic subdural hematoma	Antecedent trauma; may have subacute onset; altered level of consciousness or neurologic deficit may be present
Acute severe hypertension	Marked blood pressure elevation (systolic > 210 mm Hg or diastolic > 120 mm Hg); may have confusion or irritability
Benign intracranial hypertension (pseudotumor cerebri)	Often abrupt onset; associated with nausea, vomiting, dizziness, blurred vision, and papilledema; may have cranial nerve V1 palsy; aggravated by coughing, straining, or changing position
Carbon monoxide poisoning	May be insidious or associated with dyspnea; occurs more commonly in colder months
Carotid artery dissection	Cause of stroke; can be spontaneous or follow minor trauma or sudden neck movement; unilateral headache or face pain; ipsilateral Horner syndrome
Cervical spondylosis	Worse with neck movement; posterior distribution; pain is neuralgic in character and sometimes referred to vertex or forehead; more common in older patients
Cluster headache	Uncommon; sudden onset; duration of minutes to hours; repeats over a course of weeks, then may disappear for months or years; unilateral lacrimation and nasal congestion; severe unilateral and periorbital pain; more common in men; patient is restless during episode
Encephalitis	Neurologic abnormalities, confusion, altered mental status or level of consciousness
Frontal sinusitis	Usually worse when lying down; nasal congestion; tenderness over affected sinus
Greater occipital neuralgia	Occipital location; tenderness at base of skull; pain is neuralgic in character and referred to vertex or forehead
Intracranial neoplasm	Worse on awakening; generally progressive; aggravated by coughing, straining, or changing position
Medication-induced headache	Chronic headache with few features of migraine; tends to occur daily; hormone therapy and hormonal contraceptives are frequent culprits; includes analgesic rebound
Meningitis	Fever; meningeal signs
Postconcussion syndrome	Antecedent head trauma; vertigo, lightheadedness; poor concentration and memory; lack of energy; irritability and anxiety
Subarachnoid hemorrhage	Explosive onset of severe headache; 10% preceded by sentinel headaches
Temporal arteritis	Almost exclusively in patients older than 50 years; associated with tenderness of scalp or temporal artery and jaw claudication; visual changes
Temporomandibular joint disorder	Pain generally involves the temporomandibular joint and temporal areas; associated with symptoms when chewing
Tension-type headache	Common; duration of 30 minutes to seven hours; typically bilateral; nonpulsating; mild to moderate intensity without limiting activity; no nausea or vomiting
Trigeminal neuralgia	Brief episodes of sharp, stabbing pain and trigeminal nerve face distribution