Carotid body tumour

• Paragangliomas of the head and neck at carotid bifurcation → splays ICA & ECA (“lyre sign”).
• Often bilateral/multiple (esp. familial). So, bilateral carotid body tumours → think SDHx workup.
• Shamblin class (I–III) based on degree of carotid encasement → correlates with surgical difficulty.

Differential diagnosis

By location (carotid space)

• Vagal schwannoma
  • Often less vascular, may cause smooth fusiform expansion along nerve with cystic change, no intense early enhancement.
• Hypervascular nodal metastases (e.g. thyroid, RCC)
  • Nodal distribution, clinical context of primary malignancy.
  • Lack classic splaying/displacement pattern.