<prompt> Which structure is preserved during modified radical neck dissection?Phrenic nerveSubmandibular glandSternocleidomastoidThoracic duct  <response>: Sternocleidomastoid muscle is preserved during modified radical neck dissection. Radical Neck Dissection Modified Radical Neck Dissection Removal of lymph nodes I-V spinal accessory nerve internal jugular vein sternocleidomastoid muscleQ Removal of level I-V lymph nodes with Mnemonic: SISm: Type I: preserves only Spinal accessory nerveQ Type II: preserves both spinal accessory nerve and Internal jugular veinQ Type III: preserves spinal accessory nerve, internal jugular vein and Sternocleidomastoid muscleQFunctional neck dissectionQ 