Cerebral Venous Thrombosis - a new diagnosis in travel medicine.

Dr. Pfausler and colleagues report in this issue of Journal of Travel Medicine a series of patients with an interesting and potentially fatal neurovascular disorder; they raise the question, is this condition more frequent in travelers? Over a period of 18 months, Dr. Pfausler and colleagues identified five of fifteen consecutive patients presenting with occlusion of the cerebral veins who had been traveling on long distance flights. Some of these patients also had a history of diarrhea, and exposure to heat or dehydration associated with their air travel. It is important to note that their air travel experience was also associated with other precipitating factors in several of the cases. One patient had been mountaineering at high altitude and also had donated plasma. Another had severe diarrhea. A third patient was taking oral contraceptives. Whereas more than a coincidental link appears to be related to air travel, some of the authors' statements implying causality should be qualified in the absence of a larger, more formal, epidemiologic analysis. How might air travel lead to cerebral venous thrombosis? In clinical practice, thrombosis of the cerebral veins most commonly occurs after trauma or infection of the head and neck. However, thrombosis is also seen in conditions of heightened coagulability or viscosity. One could conjecture that prolonged air travel in a cabin, pressurized to the equivalent of high altitude, might lead to compensatory hemoconcentration and heightened blood viscosity, which could be aggravated further by other conditions such as diarrhea or oral contraceptive use. A critical point made by the authors is that the clinical presentation of cerebral venous thrombosis differs from that of conventional stroke. Patients with venous occlusion often present with headache and behavioral abnormalities, which often lead to a mistaken diagnosis of psychogenic illness before seizures or signs of increased intracranial pressure become obvious. Neurologists are trained to have a high index of suspicion for this condition in patients with trauma, infection, or in the peri-partal period. If the observations of Pfausler et al are confirmed, we should add prolonged air travel to the list of predisposing conditions. Cerebral venous thrombosis is a very treatable type of stroke. Major morbidity is due to increased intracranial pressure, which can be relieved by steroids or dehydrating agents. Treatment of underlying infection or hypercoagulability is critical. In the past, most patients were given anticoagulants, despite the risk of hemorrhage into a venous infarct. If the major draining veins of the brain are affected - in particular, the sagittal sinus - a malignant form of increasing intracranial pressure with high morbidity ensues. Recently, direct infusion of thrombolytic agents in the venous sinuses through a retrograde placed catheter has been used in patients with this condition. Cerebral venous thrombosis can be diagnosed readily with magnetic resonance imaging and angiography, which have largely replaced conventional angiography in suspected cases. The development of thrombolytic therapy for acute occlusive stroke and the demonstration of its efficacy and relative safety in carefully selected patients1 have focused attention on the need for ultra-fast recognition and treatment of cerebrovascular disease. As stroke enters the era of emergency therapy, all health professionals, including those who care for air travelers, should be aware of the various presentations of stroke syndromes and the need for urgent therapy.