Haemorrhagic intracranial complications associated with vaccine-induced thrombocytopenia or central venous thrombosis after COVID-19 vaccination: postulated underlying mechanisms with literature and case review.

Despite the unequivocal medical and social advantages of introducing vaccines against the novel coronavirus SARS-CoV-2, there were also some concerns regarding possible post-vaccination adverse events. Most of these are mild. But in rare cases, severe neurological symptoms including ischaemic stroke, intracranial haemorrhage (ICH), cerebral venous and sinus thrombosis (CVT), and thrombosis with thrombocytopenia (TTS) have been observed. Literature data suggests that thrombosis with thrombocytopenia was the major underlying cause of the ICH; dural venous sinuses/cerebral veins were indicated as the primarily affected sites of thrombosis. Our review confirms the previously documented suspicion that CVT and TTS are most likely to occur following vector-type, rather than mRNA, vaccine administration. The postulated mechanism of TTS is similar to heparin-induced thrombocytopenia (HIT) both clinically and serologically. Although ICH and VITT are very rare side effects of the COVID-19 vaccine, for patients with risk factors for thrombosis (e.g. pregnancy), physicians should carefully consider the benefit/risk ratio of vaccination.