A 35-year-old man presents with fever, severe sore throat, and neck stiffness following acute pharyngitis. CT neck at hyoid level shows enlargement of the structure marked **C** with thrombosis of the internal jugular vein. Blood cultures grow Fusobacterium necrophorum. Which of the following best describes the clinical syndrome and its primary pathophysiology?

Explanation

## Why "Lemierre syndrome — septic thrombophlebitis of the internal jugular vein within the carotid space, with risk of septic emboli to the lungs" is right Lemierre syndrome is a life-threatening septic thrombophlebitis of the internal jugular vein (IJV), which lies within the carotid space (marked **C**) as a component of the carotid sheath along with the carotid artery and vagus nerve. The condition classically follows pharyngitis and is caused by Fusobacterium necrophorum. The hallmark pathophysiology is thrombosis of the IJV within the carotid space with septic emboli to the lungs. This is the exact clinical presentation described: fever, sore throat, neck stiffness, and imaging evidence of IJV thrombosis. Per Dhingra ENT and Sutton Radiology, the carotid space is the critical anatomical compartment involved in this infection. ## Why each distractor is wrong - **Retropharyngeal abscess**: While this is a serious deep-neck infection, it occurs in the retropharyngeal space (marked **D**), which lies posterior to the pharynx and anterior to the prevertebral fascia. The clinical presentation and imaging findings (IJV thrombosis within the carotid space) are specific to Lemierre syndrome, not retropharyngeal abscess. Retropharyngeal abscess typically presents with neck stiffness and fever but does not classically involve IJV thrombosis. - **Peritonsillar abscess**: This is a localized collection within the pharyngeal mucosal space (marked **A**), not the carotid space. It presents with "hot potato voice," trismus, and uvular deviation, but does not cause IJV thrombosis or septic emboli. The organism is typically Streptococcus pyogenes, not Fusobacterium. - **Carotid body paraganglioma**: This is a benign neuroendocrine tumor arising from the carotid body (chemoreceptor tissue within the carotid space). While it does involve the carotid space, it is a tumor, not an infection, and does not present with fever, pharyngitis, or septic thrombophlebitis. It is identified radiologically by the "lyre sign" (splaying of internal and external carotid arteries). **High-Yield:** Lemierre syndrome = Fusobacterium necrophorum septic thrombophlebitis of the IJV within the carotid space after pharyngitis; high mortality if untreated; risk of septic emboli to lungs and mediastinitis. [cite: Dhingra ENT 8e; Sutton Radiology 7e Ch 56]