Initial presentation with left ICH - non hypertensive patient on no antiplatelet or anticoagulant medications - should prompt consideration of underlying lesion.  Additional information regarding prior brainstem hemorrhage (another institution) with no cause identified.  Underlying vascular malformation (AVM, cavernoma), less likely tumor.  More anterior than venous sinus thrombosis related hematoma,  but warrants exclusion if no other cause is identified.

Next investigation should be with contrast enhanced MRI/MRA.  This did not explain the temporal lobe hematoma, and there was no evidence of microbleeds or multiple cavernoma syndrome.  The prior bleed in the left posterior midbrain is well shown.  Catheter angiography should be performed as next investigation.  In this case confirming an unruptured AVM in the contralateral hemisphere, but also identifying the AVM responsible for the current bleed, and also the brainstem bleed a decade prior.

Unexplained parenchymal hemorrhage after CT and MRI should always be considered for catheter angiography.  Both carotid and vertebral arteries need to be injected; selective ICA and ECA injections are also required in most cases.