Extensive Cerebral Venous Sinus Thrombosis (CVST) After the First Dose of Pfizer-BioNTech BNT162b2 mRNA COVID-19 Vaccine without Thrombotic Thrombocytopenia Syndrome (TTS) in a Healthy Woman.

BACKGROUND COVID-19 is an acute respiratory disease caused by the SARS-CoV-2 virus, which was discovered in 2019. The high transmission and seriousness of COVID-19 necessitated the development of an effective vaccine to control spread of the disease. Multiple vaccines have been granted emergency use authorization (EUA) by the U.S. Food and Drug Administration, namely, the Pfizer-BioNTech, Moderna (mRNA), and the Johnson & Johnson/Janssen (vector) vaccines. As these novel vaccines have been used, adverse effects have been reported, ranging from mild myalgia to severe anaphylaxis and thrombotic events. Thrombotic consequences raised suspicion for the development of cerebral venous sinus thrombosis (CVST), which is a severe condition associated with occlusion of venous sinuses and disruption of the venous system flow. CASE REPORT A 28-year-old healthy woman presented with a 2-week history of persistent and progressive headache 4 days after receiving an mRNA COVID-19 vaccine (Pfizer-BioNTech). Cerebral computed tomography (CT) and CT venography confirmed the presence of extensive thrombus involving the left transverse and sigmoid sinus as well as the internal jugular vein. Furthermore, other than recent the COVID-19 vaccination, there were no precipitant risk factors in her clinical history or in the detailed laboratory work-up. CONCLUSIONS Headache associated with red flags following administration of any COVID-19 vaccine should prompt urgent neuroimaging to rule out secondary causes and determine the appropriate management. Our patient lacked the typical profile of CVST commonly seen following administration of the Oxford-Astrazeneca vaccine. The findings of low platelet count may indicate the peculiar pathophysiology of a thrombotic event associated with with the Pfizer vaccine.