FIG 2. Axial images obtained in a 55-year-old man with squamous cell carcinoma of the left temporal region, who had pain and swelling in the preauricular region, as well as facial nerve weakness.

A, Contrast-enhanced CT scan shows an infiltrating mass (m) in the left parotid gland that extends medially () between the ramus of the mandible (R) and mastoid tip (t) into the parapharyngeal space, along the expected course of the auriculotemporal nerve. Note the asymmetry in the parapharyngeal fat plane when compared with the right side. The tumor extends within the parapharyngeal space (arrowheads) anteriorly and superiorly to involve V₃ (not shown). In addition, the tumor extends along the medial margin of the mandibular ramus to infiltrate the masticator space (curved arrow). Note the preserved fat plane (straight arrow) on the right side. The scan does not show the degree of invasion of the lateral pteryoid muscle.

B, Nonenhanced T1-weighted MR image (500/11) shows the same findings as in A at a slightly lower level. Note the differences in signal intensity in the parapharyngeal fat planes (). The left parapharyngeal fat plane has slightly lower signal intensity than that of the right; this is a sign of tumor involvement (arrowheads). The fat plane medial to the ramus of the mandible on the left is completely obliterated (solid arrows), compared with that of the right (open arrow); this is a sign of tumor extension into the masticator space. Also note the slightly increased signal intensity of the lateral pterygoid muscle (P), compared with that of the right; this is consistent with involvement by tumor.

C, Contrast-agent–enhanced T1-weighted MR image (500/11) obtained with same parameters and at the same level as in B shows no substantial asymmetry in the retromandibular regions (arrows) and parapharyngeal spaces (). The fat plane medial to the ramus of the mandible (black arrowheads) seems to be intact, when compared with that on the right (white arrowhead). Without the nonenhanced T1-weighted MR images, the full extent of the tumor would have been undiagnosed.