Headaches

Dissections and CVST
Computed tomography and LP may miss some uncommon conditions associated with thunderclap headache that require some form of advanced imaging (Table 2).^3,21 The more common of these include dissections and CVST, which appear to be diagnosed with increasing frequency. Both carotid and vertebral artery dissections can present with isolated head or neck pain without any neurological symptoms or signs during the highly variable phase after the intimal tear has occurred, but before downstream ischemia or infarction occurs.²² Approximately 15% of patients with CVST present with thunderclap headache, and roughly half of patients with CVST will show some abnormality on CT; however, CT venography or MR venography is necessary to confirm the diagnosis.²³ These two modalities are probably equivalent in sensitivity.

Other Uncommon Conditions
There is a short list of other uncommon conditions: pituitary apoplexy, cerebellar infarction, and some vascular disorders. Patients with pituitary apoplexy (infarction of the gland usually due to bleeding into a previously undiagnosed adenoma) present with headache, symptoms of endocrine insufficiency, and visual field cuts—classically the bitemporal hemianopia due to the tumor pushing upwards on the optic chiasm.²⁴ Some of these patients will have blood in the CSF, simulating an SAH. Dedicated CT or, preferably, MRI of the sella turcica is diagnostic. Cerebellar infarction can cause thunderclap headache and is generally accompanied by nonspecific symptoms such as vomiting and dizziness.

RCVS AND PRES
Emergency physicians should be aware of two other conditions associated with thunderclap headache: RCVS and posterior reversible encephalopathy syndrome (PRES). Reversible cerebral vasoconstriction syndrome is associated with reversible cerebral arterial spasm.²⁵ Patients often have multiple thunderclap headaches over days to weeks, a pattern which is almost pathognomonic of RCVS. Risk factors include postpartum state, exposure to vasoactive drugs and immunosuppressive agents, catecholamine secreting tumors and others.^3,25

In PRES, patients generally present with headache (thunderclap or otherwise), visual symptoms, and seizures.²⁶ Blood pressure is usually, but not invariably, elevated in PRES, which is strongly related to hypertensive encephalopathy. There is also overlap between RCVS and PRES.²⁷

Pregnant and Postpartum Patients
Lastly, one special circumstance merits discussion. Most headaches in pregnant and postpartum women are migraine and tension-related headaches. However EPs should have a very low threshold for advanced imaging in these patients with severe headache, who are at risk for RCVS, PRES, CVST, stroke, and low-pressure headaches.²⁷ Some, but not all, of these conditions are eclampsia-related, and the risk if highest in late pregnancy or in the weeks afterward. 

Conclusion

Despite the long differential diagnosis for thunderclap headache, most patients have primary headache disorders. As with many high-risk but low-frequency problems in EM, one must develop an organized diagnostic approach. Ideally, EPs should communicate the clinical situation to their radiology consultants to maximize the information to be acquired by imaging.²⁸ Assuming a normal physical examination, one has to use clues in the history and epidemiological context to decide which patients to work up beyond the standard SAH evaluation.

Dr Edlow is a professor, department of medicine, Harvard Medical School; and vice-chair of emergency medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts. 

Unusual Causes of Headache

Allison Tadros MD; Joseph Minardi, MD

In evaluating patients presenting with severe headache, there are unusual and life-threatening etiologies EPs should include in the differential diagnosis.

Providers of acute care have been well educated on the red flags, work up, and treatment of life-threatening causes of headache such as intracranial bleeding and meningitis. However, there are other unusual but important headache etiologies and syndromes of which they also should be aware. For example, one of these conditions, cerebral venous sinus thrombosis (CVST), may have serious morbidity and mortality if not diagnosed and treated promptly. Another, giant cell arteritis (GCA), may lead to permanent blindness if not recognized. Other etiologies, while not quite as serious in nature, are still important to be acquainted with in order to provide relief of patient’s symptoms and appropriate referral. This article discusses the signs, symptoms, workup, and treatment of CVST; occipital neuralgia; short-lasting, unilateral, neuralgiform headache attacks with conjunctival injection and tearing (SUNCT); idiopathic intracranial hypertension (IIH); GCA; and indomethacin-responsive headache syndromes (IRHS).

Cerebral Venous Sinus Thrombosis

Cerebral venous sinus thrombosis (also referred to as cavernous venous thrombosis) represents about 1% of all strokes.^1,2 While this condition is thought to be uncommon, no epidemiologic studies are currently available.² In contrast to other forms of stroke, women and children are more commonly affected, with most patients presenting younger than the age 50 years.^3,4 Thrombosis may occur in the cerebral veins, the major sinuses, or both, and lead to brain edema, venous infarction, and intracranial hypertension.¹