This is subacute meningitis (headache, neck stiffness, Kernig sign) in a likely immunocompromised prisoner (weight loss, diarrhoea, cough – think TB/HIV) with blurred vision suggesting raised ICP. Before the lumbar puncture, a CT head is indicated when there are signs of raised ICP (optic disc swelling) or an immunocompromised state, to exclude a mass lesion and herniation risk. CXR, sputum ZN and CD4 are useful later but do not come before making the LP safe.