Large left cerebellar hemisphere haemorrhage that extends across the midline and results in significant mass effect. There is almost complete effacement of the fourth ventricle, and this results in hydrocephalus. The vermis bulges into the quadrigeminal cistern, but there is no significant cerebellar tonsillar herniation.
Layering of intraventricular haemorrhage within both trigones. Periventricular high FLAIR signal due to transependymal oedema.
Conclusion:
Large posterior fossa haemorrhage, centred in the left cerebellar hemisphere, results in obstructive hydrocephalus and ascending transtentorial herniation.