COVID-19 vaccine
In March 2021, the European Medicines Agency (EMA) announced that out of the around 20 million people who had received the Oxford–AstraZeneca COVID-19 vaccine, general blood clotting rates were normal, but that it had identified seven cases of disseminated intravascular coagulation, and eighteen cases of cerebral venous sinus thrombosis. It had been proposed that inadvertent injection of COVID-19 vaccine into deltoid muscle vasculature may result in vaccine distribution to distant tissues that may be causing these rare adverse reactions. A causal link with the vaccine, however, had not been proven, but the EMA decided to conduct further analysis and to inform recipients of the remote possibility of such rare syndromes. EMA confirmed that the vaccines benefits still outweigh the risks and later released updated product information. and issued warnings to patients and healthcare professionals. The British Medicines and Healthcare products Regulatory Agency (MHRA) confirmed 79 cases of thrombosis, including 19 fatalities, within the first 20 million vaccinations in Great Britain. Guidelines on management of suspected cases was issued by the British Society for Haematology; it discouraged the use of heparin until it was clearer that heparin would not aggravate the thrombosis. On 13 April 2021 the Centers for Disease Control and Prevention paused the use of the Janssen COVID-19 vaccine in the United States due to six cases of CVST that occurred 6 to 13 days after administration. The recommended pause was lifted on 23 April 2021 following a safety review.
Causes
Disorders that cause, or increase the risk for systemic venous thrombosis are associated with central venous thromboses. In children, head and neck infections and acute systemic illnesses are the primary cause of central venous thrombosis. Cerebral venous sinus thrombosis is more common in particular situations. 85% of people have at least one of these risk factors:
Thrombophilia, a tendency to develop blood clots due to abnormalities in coagulation, e.g. factor V Leiden, deficiency of protein C, protein S or antithrombin, or related problems
Nephrotic syndrome, a kidney problem causing protein loss in the urine
Chronic inflammatory diseases, such as inflammatory bowel disease, lupus and Behçets disease
Pregnancy and puerperium (the period after giving birth)
Particular blood disorders, especially polycythemia vera and paroxysmal nocturnal hemoglobinuria
Use of estrogen-containing forms of hormonal contraception
Meningitis and infections of the ear, nose and throat area such as mastoiditis and sinusitis
Direct injury to the venous sinuses
Medical procedures in the head and neck area
Obesity, especially in combination with oral contraceptive use 
Sickle cell anemia
Dehydration, primarily in infants and children
Homocysteinemia
Homocystinuria

Diagnosis
The diagnosis may be suspected on the basis of the symptoms, for example the combination of headache, signs of raised intracranial pressure and focal neurological abnormalities, or when alternative causes of headache and neurological abnormalities, such as a subarachnoid hemorrhage, have been excluded. Imaging
There are various neuroimaging investigations that may detect cerebral sinus thrombosis.