Transverse discrepancy is not easily recognized by the patient and the orthodontic envelope of discrepancy is reportedly narrow in the transverse direction, which is why surgically assisted palatal expansion is recommended for the correction of maxillary transverse deficiencies in grown-up patients. However, in case of transverse deficiencies, the timing and modality for the transverse correction is often questioned. The validity of either surgical or nonsurgical treatment possibilities need to be discussed based on the following aspects.

Key discussion points:
- Is the MARPE must for orthopedic expansion in adults? Can regular RPE split the suture?
- If yes, then why bother to use MARPE, using additional miniscrews?
- Again, why MARPE, not bone-borne RPE?
- How about the stability after MARPE?
- What is the success rate of suture separation? What are the solutions for possible non-separation?
- Does failure of separation mean SARPE? If not, what is in-between?
- What is the expansion protocol? ‘rapid for adult’ and ‘slow for child’? Or the opposite?
- In case of nonseparation, more rapid or more slow expansion?
- RPE for children vs MARPE for adults? Or the opposite?
- Does expansion enlarge airway? If so, when?