On contrast-enhanced CT, a 'salt and pepper' pattern within a highly vascular neck mass located at the carotid bifurcation is characteristic of:

• A Schwannoma of the vagus nerve
• B Carotid body paraganglioma ✓
• C Glomus vagale paraganglioma
• D Reactive lymph node

Explanation

Carotid body tumour (paraganglioma) at the carotid bifurcation shows a 'salt and pepper' appearance on MRI (T2-weighted) due to multiple flow voids (dark 'pepper') within a hyperintense mass ('salt'), reflecting its markedly vascular nature. On CT it shows intense homogeneous enhancement. The pathognomonic finding is the 'lyre sign' — splaying/widening of the internal and external carotid arteries by the interposed mass at the bifurcation. Schwannomas displace but do not splay the carotids; they are located along the vagus nerve in the carotid space. Glomus vagale is higher, along the vagus in the post-styloid parapharyngeal space.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.