Polymicrobial abscess in space between posterior pharyngeal wall and prevertebral fascia
Adults: Due to direct extension of purulent debris from adjacent site (e.g. Ludwig's angina)
More likely to extend into the mediastinum
Children: Due to suppurative changes within a lymph node (primary infection elsewhere in head or neck)
Trauma: Direct inoculation (e.g. child falling with stick in mouth)
Patients may prefer to lay supine to prevent abscess and edematous posterior wall to collapse into airway, so patients should not be forced to sit up
More likely to extend into the mediastinum
Retropharyngeal abscess
Streptococcal pharyngitis 
Peritonsillar cellulitis
Neisseria gonorrhoeae
Epiglottitis
Diphtheria 
Peritonsillar abscess
Bacterial Tracheitis