Table 3.

Differential Diagnosis of Post-Styloid Retropharyngeal Masses: Imaging Features on MRI and Molecular Imaging

	PGL	Nodal Metastasis	Schwannoma	Neurofibroma
MRI	Flow voids (salt-and-pepper appearance on T2-weighted images)	Variable appearance on spin-echo images	Moderate to high signal intensity on T2	Moderate to high signal intensity on T2 Central low signal on T2 may be seen (target sign)
	Rapid (numerous arterial feeders), intense and homogeneous enhancement	Heterogeneous enhancement	Heterogeneous enhancement in large tumors with degenerative changes (cystic, pseudocystic)	Moderate and delayed homogeneous enhancement
[18F]FDG	Moderate to high uptake (highly elevated in SDHx-tumors)	Low to high uptake depending on the primary tumor	Low to high uptake (even in benign cases)	Low uptake (high uptake values in malignant forms)
[18F]FDOPA	High uptake	No significant uptake	No significant uptake	No significant uptake
SST-based imaginga	High uptake	No significant uptake (possible high uptake in nodal metastases from thyroid cancers of follicular origin or nasopharyngeal cancers)	No significant uptake	No significant uptake

^aSST-based imaging is somatostatin receptor imaging with octreoscan or ⁶⁸Ga-labeled somatostatin analogs.