A male Shyam, age 30 years presented with Trismus, fever, swelling pushing the tonsils medially and spreading laterally posterior to the middle sternocleidomastoid. He gives an h/o excision of 3rd molar a few days back for dental caries. The diagnosis is -
Clinical features of parapharyngeal abscess

Sixty percent of patients develop it as a complication of tonsillitis or tonsillectomy and 40 percent as a result of either infection or extraction of the lower third molar tooth. Mastoid infection can extend into space on rare occasions.
There is fever and marked trismus because of spasm in medial pterygoid muscle.
The tonsil, if it is normal, is pushed medially.
The most marked swelling is in the neck at the posterior part of the middle third of the sternomastoid (behind the angle of jaw). There may also be swelling in the retromolar area.
There is torticollis (due to spasm of prevertebral muscles), sore throat, marked odynophagia and signs of toxaemia.
Further extension of the disease may cause involvement of IX, X, XI, XII cranial nerve and sympathetic chain.
Retropharyngeal abscess
Ludwig's angina
Submental abscess
Parapharyngeal abscess