Oropharynx

Most of the oropharyngeal sub-sites are easily evaluated in the axial plane with cross-sectional imaging. Pharyngeal wall lesions rarely penetrate the tough pharyngo-basilar fascia in their early stages. Retropharyngeal extension and adenopathy are clinically occult and must be excluded radiographically. Invasion of the masticator space by tonsillar lesions (Figure 3-17) can be detected with a good contrast-enhanced scan. The index of suspicion must be high particularly when trismus is present. Axial views also outline base of tongue lesions across the glosso-tonsillar sulcus, which may be difficult to appreciate clinically. Base of tongue lesions are best supplemented by sagittal views to outline the status of the preepiglottic space. This also determines the extent of involvement anteriorly into the intrinsic muscles of the tongue for accurate T staging.

Follow-up images need careful correlation with pretreatment scans because of the variability of native lymphoid tissue during treatment. Often regrowth of lymphoid tissue produces pseudotumor contralateral to the original primary tumor. Misinterpretation of this phenomenon could falsely suggest locoregional failure. Imaging artifact can be avoided in the oropharynx with direct coronal views behind the dental work that would otherwise obscure the lesion in the axial plane.

Figure 3-13. Axial contrast T1-weighted MR image through skull base. (1) Neurotropic intracranial extension along cisternal segment of Vth nerve. (2) Leptomeningeal growth along cerebellar folia. (3) Operative bed of original ethmoid sinus tumor remains free of disease.

Figure 3-14. CT images of palate tumor with centripetal neurotrophic extension. Upper panel: axial bone (L) and tissue (R) windows through palate. Lower panel: coronal (L) and para-sagittal (R) tissue windows. (1) Palate tumor involving hard and soft segments. (2) Extension upward through widened left greater palatine foramen. (3) Normal bilateral palatine canals.

Figure 3-14. CT images of palate tumor with centripetal neurotrophic extension. Upper panel: axial bone (L) and tissue (R) windows through palate. Lower panel: coronal (L) and para-sagittal (R) tissue windows. (1) Palate tumor involving hard and soft segments. (2) Extension upward through widened left greater palatine foramen. (3) Normal bilateral palatine canals.

Soft palate lesions are difficult to discriminate with conventional imaging because of the curved contour of the structure, the poor conspicuity of these lesions and motion artifact from the soft palate resting on the tongue. This organ is best imaged in the semi-coronal plane (Figure 3-18) with special attention to the tonsillar margin.

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