What is the diagnosis, and why?
Probably a subdural haemorrhage. While its almost-lentiform shape suggests it may be an extradural haemorrhage and there is no obvious underlying contusion, bone windows reveal that it crosses the lambdoid suture. This suggests it is probably a subdural haemorrhage.
Biconvex (lentiform) extra-axial hyperdense collection overlying the left parietal and occipital lobe. On bone window, it can be seen to cross a normal appearing suture (no diastasis or fracture). There is, however, significant overlying scalp haematoma. No definite underlying contusion.
- CT (bone window):