Dear Sara,
Thus far, diagnostic procedures have proved negative, but they have not yet ruled out organic factors to explain your son's condition. The sleep deprived EEG will be useful. Arguing against the possibility of conversion disorder, at least insofar as the information you provided in your note is concerned, is the absence of conflicts or stressors that would precede the initiation or exacerbation of the seizure activity. There is certainly reason to be skeptical about the diagnosis of conversion disorder, particularly because your son has already displayed some neurologically-based problems.
Sometimes a person can be conscious but, at the same time, not responsive to his surroundings (e.g., not responding to voices or other sounds). You might speak with the authors of the reports to determine precisely what was meant by the terms.