Interferential stimulation is being used for Piriformis Syndrome as well as laser and heat.   The post by Chiropractic Doctor first tries to rule out other potential problems such as:

1. Gluteus muscle strain
2. Ischial bursitis
3. Lumbar disc disease

   and then goes on to prescribe treatment with interferential. 
It is now with the use of the Infrex Plus at home that more options become available because the patient can self treat upon satisfactory diagnosis.

The Infrex Plus may change many treatment protocols because of the carryover pain relief effect that is emerging when a patient can treat couple of times day and then the pain relief period gets longer and longer.  In this case the stretching etc. as well as use of heat/cold should be utilized also.  It's doubtful that only the use of interferential without having patient engagement in other rehab. activities would be enough.