This could be a subarachnoid haemorrhage (SAH). The typical presentation is of thunderclap headache, with neurological deficits and/or confusion. The best method to investigate this is by CT.
The GCS can be used to grade severity of subarachnoid haemorrhages. In some units, a GCS >14 with no neurological deficit would be managed by the neurologists, while the rest go to neurosurgical care. In Edinburgh, all SAHs are managed by the neurosurgical team with interventional neuro-radiologists.
Presentation
Sudden onset headache. Disorientation, confusion. No previous imaging.