CASE REPORT

A 23 year old moderately obese white woman with a recent diagnosis of BIH three days previously presented to another rural ED with worsening headaches, confusion, and new onset seizure. On arrival to that ED she was noted to be febrile, slightly disoriented, but able to follow commands. Diagnostic testing at that facility included a head CT, interpreted as negative by that institution’s radiologist. Therapeutic interventions included the administration of ceftriaxone and acyclovir. The treating physician wanted to perform a lumbar puncture but the family refused and requested transfer to our facility stating they wanted “the experts”. The patient was transferred to our facility, a tertiary care referral centre, via aeromedical transport with a suspected diagnosis of worsening BIH versus meningitis. The time from presentation to the transferring facility to arrival in our emergency department was less than three hours. The patient arrived at our hospital unable to provide any additional history because of her decreased mentation. Family members gave some insight into the patient’s recent history. The patient three days previously had visited an emergency department with complaints of headache. At that visit she was diagnosed with BIH based on the results of a negative head CT, and a lumbar puncture showing raised intracranial pressure; a magnetic resonance imaging (MRI) study was not performed or scheduled for in the near future. An outpatient neurology appointment was to be made by the patient. The family stated that the patient had been having increased headache over the past two days as well as subjective fevers. She was an otherwise healthy young woman, the only drug she was taking was oral contraceptives, and her social history was noticeable only for being a smoker of one pack a day.

Examination on arrival in our emergency department revealed a lethargic woman, a definite change from the report given to the accepting physician before transfer. The patient did not follow any commands, opened eyes to physical stimulation, localised to pain, and spontaneously moved all extremities. Secondary to concerns that the patient was suffering from a significant neurological insult, as well as concerns for airway protection, a decision was made to undergo rapid sequence intubation and provide mechanical ventilation. A repeat non-contrast head CT was immediately performed showing thrombosis in the superior sagital sinus (SSS), both transverse sinuses (fig 1), and straight sinus. There was also diffuse cerebral swelling. Both our neuroradiologists and neurosurgeons felt the head CT was consistent with a diagnosis of DST. A review of a copy of the CT scan performed at the transferring facility brought by the aeromedical transport team demonstrated subtle findings suggestive of DST, specifically some hyperdensities seen within the SSS. Of note there was demonstration of maxillary sinusitis on both the CT done at the referring facility as well as our facility. Clinically, the patient’s neurological examination continued to deteriorate. Neurosurgery did not start heparin treatment as they thought the heparin would not be beneficial at this late stage of illness. Their plans were to perform cerebral angiography and possible lysis of clot. The cerebral angiogram, unfortunately, showed no cerebral blood flow. The family withdrew support and no necropsy was performed by the family’s request. The cause of death listed on the death certificate was dural sinus thrombosis.

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Figure 1

Unenhanced axial CT showing thrombosis of the transverse sinuses.

DISCUSSION

Although described in the neurology and neurosurgery literature, DST is not well described in the emergency medicine literature. Major emergency medicine textbooks contain little if any information on this topic. To the best of our knowledge there are only two papers describing DST in the emergency medicine literature: a case report from 1991¹ and a brief case report/discussion in 2002.² Emergency physicians are called upon daily to evaluate severe headaches and other neurological complaints and must know the clinical presentation and the diagnostic tests to make the diagnosis of DST. Furthermore, they must resist the urge to diagnose or believe a diagnosis of BIH without a confirmatory MRI/magnetic resonance venography (MRV) study.

The true incidence of DST is unknown because the generally good prognosis (less than 10% mortality) and heterogeneous clinical signs probably result in a good percentage of clinically undetected cases. Because of heightened awareness and better diagnostic testing it is being diagnosed more frequently. DST has over 100 recognised aetiologies that encompass all causes of deep vein thrombosis as well as a number of local and regional causes.^3,4 The proportion of cases of unknown cause is about 20%–30%.³ Important distinction is made between infective aetiologies, which comprise 8% of DST, and non-infective causes. Infective aetiologies are usually staphylococcal infections of the face such as sinusitis. The non-infective aetiologies are principally inflammatory processes such as lupus, Behçet’s disease, inflammatory bowel diseases, and any hypercoagulable state such as pregnancy, malignancy, and Factor V Leiden.⁵ It appears the aetiology of DST in our patient may have been infectious given the maxillary sinusitis seen on CT scan, or it may have been the result of hypercoagulability from oral contraceptive use and smoking.

Presentations are very diverse in DST. Headache is the most frequent symptom and often the presenting one, being present in 70% to 90% of patients. Focal motor or sensory deficits, dysphagia, seizures, and abnormal mentation each occur in 50% to 75% of cases. Papilledema occurs in 12% to 43% of patients.³ Mode of onset of symptoms is also highly variable ranging from acute presentations (less than 48 hours) to subacute presentations (48 hours to 30 days) and finally chronic presentations (greater than 30 days). The most homogeneous pattern of presentation is isolated intracranial hypertension with headache and papilledema, mimicking BIH, and is present in 37% of cases.³ Outcomes are unpredictable. There are acute cases, as ours was, which can have a fulminating course leading to death in a few days whereas others can recover rapidly either with or without sequelae. There are chronic cases that can result in neurological sequelae and others that can recover spontaneously.⁶

In suspected DST, a CT scan with and without contrast injection should be the first neuroimaging study to be performed. Direct signs of DST include the cord sign, the dense triangle, and the empty delta sign. The cord sign, rarely seen on unenhanced CT scan, represents the visualisation of a thrombosed cortical vein. The dense triangle is also rare and represents the spontaneous SSS opacification by freshly congealed blood. The empty delta sign is seen in 30% of cases on enhanced CT scans and is the result of opacification of collateral veins in the SSS wall, contrasting with the non-injection of the clot inside the sinus. Indirect and non-specific abnormalities include intense contrast enhancement of falx and tentorium, the presence of small ventricles with swelling, the presence of diffuse low density suggestive of oedema, and haemorrhagic and non-haemorrhagic venous infarcts.³ The CT scan is normal in up to 26% of patients with verified DST³ and up to 54% of patients that present with isolated intracranial hypertension.⁷ Examination of the cerebral spinal fluid is not terribly helpful in establishing the diagnosis of DST as there is no pathognomonic finding. Abnormalities include raised pressure (>200 mm), increased protein content, presence of red blood cells, and pleocytosis.⁶ Furthermore, cerebral spinal fluid studies are negative except for raised pressure in 75% of patients with DST who present with isolated raised intracranial pressure.⁷ MRI combined with MRV have become the radiographic tests of choice for the diagnosis of DST and have replaced the more invasive and expensive cerebral angiography.^8,9 MRI alone may result in false positive and false negative readings and the addition of MRV can result in added confidence in the inclusion or exclusion of the diagnosis.¹⁰ Another option is cerebral CT venography, which has a sensitivity at least as great as MRV.¹¹

There are few therapeutic trials of DST resulting in a lack of any clear benefit of any specific treatment option. Although somewhat controversial in efficacy given mixed results from two prospective randomised trials,^12,13 heparin is considered first line treatment in the initial management of DST. This is based on the results of a meta-analysis as well as several retrospective and prospective case series, and influenced by the fact that it seems to be very safe even in the presence of haemorrhagic lesions.⁴ Another option gaining some support is thrombolysis via selective catheterisation of the occluded sinus. It obviously can only be performed in very select centres and it carries an undetermined benefit to risk ratio. It may be indicated in those cases where clinical condition is worsening despite adequate anticoagulation and optimal treatment of the possible causative factors.⁴

DST carries an amazingly diverse array of clinical presentations. It must be in the differential diagnosis of anyone who presents with headaches or other neurological complaints. The emergency physician must maintain a high degree of suspicion for this disease especially in the setting of a patient that may easily be diagnosed as simply having BIH—a patient presenting with complaints of headache, with a normal head CT and raised intracranial pressure on lumbar puncture. It has been reported that DST can be identified in 26% of patients presenting with symptoms and signs typical of BIH.¹⁴ As CT results are often non-specific, MRI with MRV should be the imaging modality of choice, and the diagnosis of BIH should be highly questioned if these studies have not been performed. Treatment begins with unfractionated heparin or low molecular weight heparin as these seem to be safe and effective. Perhaps the outcome of our patient may have been different if DST would have been suspected or diagnosed at the initial hospital visit and appropriate treatment started. Even if a MRI/MRV study was not able to be obtained that day, starting heparin treatment until a definitive diagnosis could be made could have been potentially life saving as there are no reported contraindications to anticoagulating patients with BIH. It is difficult to say if heparin treatment would have been beneficial if started at the transferring facility beause it was so late in the patient’s course of illness, however there are reports of dramatic improvement the day after starting heparin treatment in patients with DST who were clinically deteriorating.⁶ This case and subsequent discussion should hopefully convince the emergency physician to strive for early diagnosis and treatment of this illness that is unpredictable in both its presentation and its outcome.