Patient 1. A 49-year-old woman presented with headache and nausea on awakening which progressively worsened over the course of a few hours. She also noticed right arm clumsiness. CT head on admission showed subarachnoid blood predominately in the vertex. CT angiogram and venogram were normal but right transverse sinus thrombus was found on digital subtraction angiography. Patient 2. A 48-year-old woman was woken with a severe headache and neck pain. CT head on admission showed subarachnoid blood in the chiasmatic cistern, sylvian fissure and pre-pontine cistern. CT angiogram and initial digital subtraction angiography were normal. Repeat digital subtraction angiography a week later showed a filling defect in the left lateral sinus and internal jugular vein. Both patients were anticoagulated and improved clinically. The likely mechanism for sub-arachnoid blood in this context is increased pressure in the subarachnoid cerebral venous system transmitted from the dural system via veins including the veins of Labbé and Galen.Conclusion
Venous sinus thrombosis is a rare but treatable cause of subarachnoid haemorrhage and should be considered in cases of non-aneurysmal subarachnoid haemorrhage.