Headache is a very common chief complaint in emergency department (ED) presentations. Of these patients, 98 percent will have a benign etiology. Of the remaining two percent, one percent will be reliably diagnosed on unenhanced CT or lumbar puncture (LP), however the other one percent cannot be ruled out on unenhanced CT or LP.1 One example of a potentially life-threatening condition that most often presents with headache and cannot be ruled out with unenhanced CT and LP is cerebral venous thrombosis (CVT). Unenhanced CT has only a 41 percent to 73 percent sensitivity for the diagnosis of CVT, with CT venogram being the diagnostic test of choice in the ED, and MRI venogram being the gold standard.2 This is just one reason the diagnosis is difficult to make in the ED. Another reason is that clinical manifestations are highly variable and nonspecific, as there are a multitude of possible locations of thrombosis that do not follow a typical arterial ischemic stroke distribution, and evolution over time is variable. The median time to diagnosis between initial presentation and diagnosis is seven days, however, CVT can present like a subarachnoid hemorrhage with a “thunderclap” headache, or gradually over days to weeks.3 In fact, the headache of CVT has no specific characteristics, most often being diffuse, progressive, and severe, but sometimes unilateral, sudden, or mild, and sometimes migraine-like. Pain can originate from tension on the vein itself or from raised intracerebral pressure which causes diffuse headache. It may be positional (worse in the supine position) and may be aggravated by Valsalva, reflecting raised intracerebral pressure. Features that make the diagnosis of CVT less likely include purely unilateral pain, scintillating scotoma, and recurrent or episodic headache. Return visits to the ED for the same headache should be considered a risk factor. While headache is the most common chief complaint, others include seizure, encephalopathy, and focal neurologic symptoms.4
An understanding of the pathophysiology helps to explain the myriad clinical possibilities. When a venous clot forms, venous and cerebrospinal fluid drainage suffer, leading to upstream increased pressures. Raised intracranial pressure, cerebral edema, hydrocephalus and decreased cerebral perfusion pressure may lead to brain ischemia and subsequent hemorrhagic transformation, which are often devastating. With this pathophysiology in mind, it is no surprise that CVT can present with various clinical findings including vision changes, diplopia, nausea and vomiting, papilledema, cranial nerve deficits, encephalopathy, neck pain, proptosis, chemosis, mastoid pain, hemiparesis, dysarthria, aphasia, seizures, bilateral motor deficits and pulsatile tinnitus.5 Nonetheless, CVT can be divided into four recognized syndromes, from most common to rarest: isolated elevated intracranial hypertension, focal neurologic syndrome, diffuse encephalopathy, and cavernous sinus syndrome, which may help the clinician in assessing pretest probability.