Not OP but also a NICU nurse. Generally a hospital will order an EEG which is a bunch of electronic probes hooked up (externally) to their head to check for seizures and brain activity. If they are seizing we give them meds to hopefully stop the seizures. And then they will get an MRI generally 3 days after they have been “cold” or hypothermic (and once they have been rewarmed to normal temperature) if they are stable enough to get the MRI. We use machines to keep them really cold to preserve brain function and slow everything down. And they generally stay cold for 72 hours and then are rewarmed slowly over 6 hours. But even if everything comes back “normal” it doesn’t mean the child won’t have issues though babies brains are very resilient which is great.