A 42-year-old woman presents to the Emergency department with a sudden onset severe headache accompanied by nausea and vomiting. She has also experienced intermittent uncontrollable twitching of her left hand and noticed blurring of vision in the last hour. The patient has a history of psoriatic arthropathy and is recovering from gastroenteritis. She is a smoker and drinks approximately 10 units of alcohol per week. On examination, she appears dehydrated with mild papilloedema and increased tone in the left arm and leg. A CT brain scan reveals an enhancing lesion within the right frontal cortical white matter junction associated with haemorrhage and cerebral oedema. Based on these findings, what is the most likely cause of the patient’s neurological presentation?