A 34-year-old gentleman presented to the Emergency Department with drowsiness, agitation and right sided weakness following a 10-day history of constant, holocephalic headache and a 2-day history of photophobia and vomiting. He had received the AZ ChAdOx1 nCoV-19 vaccine 14 days previously. He had a history of bipolar disorder treated with lithium and was otherwise well. On admission the Glasgow Coma Score (GCS) was 10 (eyes 4, voice 3, motor 3), his pupils were equal and reactive and he had a dense right sided hemiparesis. Multiple discrete petechiae were noted on the legs and a bruise was apparent on the left shoulder. Computed tomography (CT) of the brain revealed a superior sagittal sinus hyperdensity associated with a 47 mm intraparenchymal haemorrhage in the left perirolandic region (Fig. 1). A CT venogram confirmed an extensive cerebral venous sinus thrombosis (CVST) in the superior sagittal sinus extending to both transverse venous sinuses, and thrombosis in the left vein of Trolard. Whole body CT revealed a right lower lobe segmental pulmonary embolus. His blood tests revealed a normal haemoglobin 152 g/L and white cell count 11.15 cells x 109/L, but low platelets (23 x 109/L) without platelet clumping or red cell fragmentation on blood film. A clotting screen revealed a raised prothrombin time of 14.8 seconds, a raised international normalised ratio (INR) of 1.5, a normal activated prothrombin time (APTT) of 23.9 seconds and a low Clauss fibrinogen of 0.7 g/L. D-dimer was significantly raised (37,293 mg/L). SARS2-CoV-2 polymerase chain reaction (PCR) from a throat swab was negative. His anti-S titre was 125.2 (≥50 is reported as detected) with a negative anti-N antibody result consistent with recent vaccination. He was found to have a lupus anticoagulant but did not have anticardiolipin or anti-β2 glycoprotein-1 antibodies. ADAMSTS13 activity was normal and AcuStarHIT-IgG was negative. He was sedated, intubated and transferred to the Intensive Care Unit (ICU). He was transfused with 2 adult units of platelets due to his thrombocytopenia and bleeding. He commenced plasma exchange with 1.5 plasma volumes using Octoplas on two occasions and received 1g/kg intravenous immunoglobulins (IVIg). Due to the emerging evidence of a potential association of the ChAdOx1 nCoV-19 vaccine with an autoimmune thrombocytopenia and concurrent bleeding, anticoagulation with heparin was avoided in favour of argatroban, a small molecule thrombin inhibitor with a short half-life of 50 minutes. Later, STAGO Asserachrom HPIA ELISA for anti-platelet factor 4 (PF4) antibodies was positive. Of note, the platelet count incremented and normalised to 191 x 109/L within two days of admission and anticoagulation continued, maintaining APTT at 1.5-3 times baseline. Despite maximal medical therapy, the GCS began to fluctuate and dilatation of the left pupil was noted with intermittently reduced responsiveness to light. Repeat CT brain scanning revealed worsened cerebral oedema with right sided midline shift and early uncal herniation. Anticoagulation was paused 8h before a decompressive hemicraniectomy and insertion of an intracranial pressure (ICP) monitor and restarted 10 h post-operatively and after a satisfactory CT scan. Persistently high ICP recordings necessitated the insertion of an external ventricular drain after stopping anticoagulation, which led to improvement. Ultimately, the monitor had to be removed due to blockage and concerns about ventriculitis, for which he received antibiotics. His condition slowly stabilised and sedation was weaned. Once surgical interventions were no longer anticipated, anticoagulation with apixaban – an oral Xa inhibitor – was commenced at 5 mg twice daily. At present, he is off ventilation with a tracheostomy and has stepped down to a high dependency unit. He has a dense right hemiparesis and aphasia.