Researchers at University College London conducted a study of people with cerebral venous thrombosis (CVT) following the COVID-19 vaccination, to provide a clearer guide for clinicians trying to diagnose and treat such patients.

For our comprehensive coverage and latest updates on COVID-19 click here.

The research, published in The Lancet, is the most detailed account of the characteristics of CVT, when it is caused by the novel condition vaccine-induced immune thrombotic thrombocytopenia (VITT). VITT is a condition characterised by a blockage of the veins and a marked reduction of platelets, blood components that are an important part of the blood clotting system. The commonest and severest manifestation of VITT is CVT, in which veins draining blood from the brain become blocked.

The study looks in detail at 70 patients with VITT-associated CVT following vaccination, who were then compared to 25 patients with CVT but without the evidence of VITT. The study provides support for the three principles of treatment established so far by the Expert Hematology Panel, based on early work at UCL and two other European sites. The use of non-heparin-based anticoagulation; give treatments to try to reduce the level of the abnormal antibody that is implicated in this condition, and avoid the strategy of trying to bring the platelet count back up to normal levels by giving platelet transfusions.

"We found that those patients who were given intravenous immunoglobulin -- the treatment in which the body is flooded with normal antibodies to try to reduce the effects of the abnormal one -- were more likely to leave hospital alive and able to live an independent life rather than depending on carers or family to look after them," Dr Alastair Webb, consultant neurologist at the John Radcliffe Hospital in Oxford said.

On the other hand, platelet transfusions were associated with a worse outcome in patients with VITT-associated CVT. Although observational data cannot prove harm from this treatment approach, the study provides support for the concern that has already been raised about the potential harm of platelet transfusions.

However, the researchers also suggest that some treatments such as intravenous immunoglobulin seem to be associated with better outcomes but caution against reading too much into the findings of the observational study, saying that reliable evidence about treatments can only be obtained in a randomised clinical trial.