Can you please explain brain aneurysm and what are the symptoms?

Brain aneurysm: Brain aneurysm is an abnormal swelling of a brain blood vessel. Symptoms may be none, or caused by compression of adjacent brain wherever the lesion is located. If the aneurysm ruptures, headache is fairly universal and severe.

Dilated: One of the named arteries expands size relative to the remainder of that vessel or normal size.( there are many tiny blood vessels ) expansion may press on something and create symptoms. More dangerous is leak, of blood under pressure and damage to, brain by disruption of tissue, or hematoma and pressure. Severe headache!