All of the following are true regarding zenkers diveiculum except

PHARYNGEAL POUCH Also called hypopharyngeal diveiculum or Zenker's diveiculum, it is a pulsion diveiculum where pharyngeal mucosa herniates through the Killian's dehiscence--a weak area between two pas of the inferior constrictor. AETIOLOGY :- Exact cause is not known. It is probably due to spasm of cricopharyngeal sphincter or its incoordinated contractions during the act of deglutition. It is usually seen after 60 years of age. PATHOLOGY :- Herniation of pouch stas in the midline. It is at first behind the oesophagus and then comes to lie on its left. Mouth of the sac is wider than the opening of oesophagus and food preferentially enters the sac. Ref:- Dhingra; pg num:-274