Can ct scan without contrast show brain aneurysm?

Unlikely: Due to resolution of a ct scan, many small aneurysms may not be seen, and, by far, the MRI would be far better, but again, it might take gadolinium. However, the cat angio could well detect an aneurysm, and this might work as well or better than a magnetic resonance angio.

Unlikely: Ct scan without contrast is unlikely to show an aneurysm unless it is very large and is calcified. A ct angiogram is a better study to visualize an aneurysm.