Question:   An 82 year old male is referred to you for dysphagia.  He brings with him a videofluoroscopic swallow study showing an upper esophageal diverticulum.  You elect to perform an external diverticulotomy and cricopharyngeal myotomy (given a history of cervical spine fusion) suspecting a Zenker's diverticulum.  To your surprise, the diverticulum sac is protruding through a muscular diastasis caudal to the cricopharyngeus.  What kind of diverticulum is this?   [Answer will be posted with next week's new question]

Answer to last week's question, Turn it Up (March 7, 2016): 

Rollover.  While neither particularly sensitive or specific to retrocochlear pathologies, this phenomenon is often seen in audiometric testing of an ear with a vestibular schwannoma.