What is the burden of cerebral venous thrombosis in British Columbia?

A doctor talks to a young woman holding her head as if in pain

Cerebral venous thrombosis (CVT) is a rare cause of stroke that predominantly affects younger patients and women, especially around the peri-partum period. Because of its rarity, it is a challenging disease to study using traditional methods. A new study, using administrative data to study Canadian incidence, patient demographics, prognosis and current treatment patterns, aims to shine a light on this rare disease and help guide physicians when providing counselling and considering treatment.

The study aims to provide an improved understanding of the burden of CVT in Canada. Characterizing who is affected by CVT, how it is diagnosed and treated, and its prognosis, will allow for the refinement of Canadian care standards and clarification of system-level performance measures for this stroke type. During the COVID-19 pandemic, interpreting baseline rates of CVT obtained from administrative data amidst new and evolving information on vaccine-induced prothrombotic immune thrombocytopenia from the AstraZeneca and Johnson and Johnson vaccines took on new importance and urgency.

Lily Zhou, a post-doctorate research fellow at the Vancouver Stroke Program, is undertaking the study under the supervision of Dr. Thalia Field, Neurologist and Associate Professor in the Faculty of Medicine at the University of British Columbia. The project is funded by the Canadian Institutes for Health Research.

Presentation of CVT can include severe headache, seizures, vision changes, focal neurological deficits, confusion, coma and death. Rates of death and disability are ~15%; over half of patients may experience lasting neurological and neuropsychiatric issues, and 25% unable to return to work. As the disease disproportionately affects young patients, its impact on quality of life, lifetime earnings and productivity can be substantial. A significant contributor of disability among CVT survivors is secondary epilepsy, reported in up to 10% of patients.

Current treatment of CVT includes initiation of anticoagulation in those without contraindications such as trauma. Depending on the anticoagulation agent selected, this treatment path can be resource-intensive and to this point the healthcare resource utilization and cost of CVT and how treatment can have an impact on this has not been characterized in the published literature.

“Given the rarity of the condition compared to other VTEs, such as deep vein thrombosis and pulmonary embolism, there is still a dearth of high-quality evidence regarding optimal choice and duration of anticoagulation therapy,” says Dr. Zhou. “Treatment strategies within the country have been variable and we are only beginning to formulate Canadian Best Practice recommendations.”

A further concern is that diagnosis of CVT is not always timely, and late diagnosis is associated with worse neurological presentation, and possibly a worse prognosis. As CVT generally affects younger, healthier people than other causes of stroke and can present with non-specific symptoms such as isolated headache, visual blurring and malaise. In addition, CVT can be difficult to diagnose without dedicated vascular neuroimaging, which can be missed in the “first-line” workup of refractory headache.

These factors, combined with the rarity of the condition, often lead to frequent delays in diagnosis. “In our own clinical experience, many CVT patients we encounter have presented to medical attention multiple times in the days to weeks preceding diagnosis, sometimes worsening clinically with the development of seizures or focal deficits before their CVT is identified,” says Dr. Zhou.

By clarifying patterns of health care usage of people with CVT prior to their diagnosis, the project also aims to develop dedicated educational materials to improve the clinical index of suspicion for CVT amongst “frontline” clinicians. This will help to reduce preventable neurological morbidity, and unnecessary health-care utilization.

PopData will link five data sets from the BC Ministry of Health with BC Cancer and Perinatal Services BC data for the project.