This patient has known PLA2G5 associated neurodegeneration, accounting for cerebral and cerebellar volume loss. 

Global hypoxic-ischemic brain injury, also known as hypoxic ischemic encephalopathy, due to a variety of reasons that resulted in prolonged brain ischemia with catastrophic neurological outcome.

The deep grey-matter and cortex are especially affected by ischemia as these are the areas with high demand for oxygen and glucose. CT usually demonstrates decreased attenuation of these structures with the reversal of grey-white matter density (reversal sign), white cerebellar sign, global brain edema, and pseudosubarachnoid hemorrhage.