Dear Nell:
Sorry to hear about your daughter. The first thing that I think of is a central canal (called a syrinx) within the brainstem and/or cervical cord. We have seen this mimic a harlequin-like event. I have read that this can be seen in lupus as part of a vasculitis, but I haven't seen it myself. I would recommend getting a MRI of the brainstem and cervical cord. If this is indeed the case, there is not much to do, but at least the indictation of lupus would be reduced and likely not at all for this symptom.
Sincerely,
CCF Neuro MD