What the widespread cortical restricted diffusion may represent?
These MRI features are strongly suggestive of a significant and global hypoxic or ischaemic cause. Less likely, this could be attributed to severe seizures. Fat embolism is a consideration also, however, it is usually more patchy and often with SWI changes, absent in this case.
There is wide diffuse abnormal signal involving all lobes of the hemispheres, characterised by cortical swelling and restricted diffusion (particularly of cortex, subcortical white matter, and deep grey matter - most notably the thalami). Generalised brain swelling is present with effacement of the basal cisterns.
Within the limitations of this scan (which does not include MRV or MRA) dural venous sinuses appear normal, and flow voids are present in the major intracranial arteries.
Air-fluid levels in both sphenoid sinuses. The orbits and calvarium appear unremarkable.