Boxer Puppy Seizure? Epilepsy? Head Shaking

Our 3 month old boxer puppy vomited last night followed by her head rocking side to side uncontrollably. No diarrhea. She appeared powerless. No known head trauma. No ear mites. We took her to the emergency room 20 minutes later and had her examined, blood drawn for tests, IV, and medication. Everything appeared to be fine and was recommended neurological tests. Anyone have a clue?