Most of these decisions are made from the pictures. A reported “small aneurysm” or “vascular malformation” tells me very little; the source images tell me almost everything. Second opinions are welcome from anywhere, and the honest answer is often that nothing needs doing.
Acute emergencies — a thunderclap headache, a suspected rupture, or a large-vessel stroke — should come by phone to the emergency line at any hour rather than by message. Whichever route you use, put the patient name and one contact number in the message so the images can be matched to the history.
These are the presentations most often investigated in the wrong direction. None of them needs to be certain before you pick up the phone.
Patients referred for an opinion are returned to you with a written note setting out the reasoning, not just the recommendation — including where surveillance rather than intervention is advised, and what should prompt re-referral.