This is a classic case of 'white cerebellum sign' associated with severe pediatric head trauma, apart from other etiologies like non-traumatic hypoxia, status epilepticus or child abuse like 'smothering'. 

Many etiologies have been postulated like vasospasm of supraclinoid middle cerebral arteries, or preferential oxygenation of posterior circulation, during severe hypoxic insult, but certainly it reflects a global severe hypoxic response.