Peritonsillar abscess (quinsy) is most commonly caused by Fusobacterium necrophorum and streptococcal species. The abscess forms between the tonsillar capsule and the superior constrictor muscle. Which nerve, if affected by deep extension, explains the trismus seen in peritonsillar abscess?

• A Pterygoid muscles spasm due to spread to pterygomandibular space involving the inferior alveolar nerve
• B Masseter spasm due to CN V3 motor root irritation
• C Internal pterygoid muscle spasm due to parapharyngeal spread and muscle irritation ✓
• D Temporalis spasm due to infratemporal fossa involvement

Explanation

Trismus in peritonsillar abscess occurs because the abscess lies immediately medial to the pterygomandibular raphe and the medial pterygoid muscle. Inflammatory spread/edema causes reflex spasm of the internal (medial) pterygoid muscle, which lies adjacent to the peritonsillar space via the parapharyngeal space. This muscle is a jaw-closer; its spasm limits mouth opening. The combination of dysphagia, drooling, muffled 'hot potato' voice, uvular deviation toward the opposite side, and trismus constitutes the classic presentation. Incision and drainage with immediate antibiotics (amoxicillin-clavulanate) is curative; tonsillectomy is considered for recurrences.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.