With a retropharyngeal and peritonsillar abscess, an abscess is a collection of pus, and retropharyngeal and peritonsillar describe where the abscess is found.
A retropharyngeal abscess develops behind the pharynx - in the tissue that lies just behind the back of the throat.
A peritonsillar abscess develops around the tonsils, particularly the palatine tonsils which are at the back of the throat.
Let’s start by better defining the locations of these spaces.
The retropharyngeal space is the region between the pharynx and vertebrae and is bound posteriorly, closer to the vertebrae, by the alar fascia and anteriorly, closer to the pharynx, by the buccopharyngeal fascia.
These fascial layers are thin fibrous layers that coat muscles, tendons, and bones muscle, and between them in the retropharyngeal space are lymph nodes.
These lymph nodes are like surveillance stations that bring in lymphatic fluid from the throat and other nearby tissue.
If there are pathogens in that lymphatic tissue, immune cells in the lymph node can respond and try to destroy the invading pathogens.
Next, is the peritonsillar region which refers to the palatine tonsils.
The palatine tonsils are on either side of the oropharynx and are attached to the soft palate at the back of the oral cavity. They’re basically dense collections of lymphatic tissue wrapped within a fibrous capsule - like tiny lymph burritos, that help defend against pathogens in the food and air.