Perineural Tumor Spread Along the Auriculotemporal Nerve

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.

Axial contrast-agent–enhanced CT images obtained at two levels in a 77-year-old man with metastatic undifferentiated carcinoma and lymphoma who had a left facial mass and facial weakness.

A, Scan shows that a homogeneous soft-tissue mass (m), which extends medially (arrowheads) along the posterior margin of the ramus (★) of the mandible, almost completely replaces the left parotid gland. This finding was interpreted as suggesting perineural tumor spread along the facial nerve main trunk and auriculotemporal nerve. Pathologic findings, however, did not confirm this. Retrospective review of the CT scans revealed that the soft-tissue mass actually was lower than the expected course of the auriculotemporal nerve.

B, Scan illustrates the correct level of the auriculotemporal nerve. No abnormality in the retromandibular region is depicted at this level. ★ indicates the posterior margin of the mandibular ramus.

Contrast-agent–enhanced T1-weighted MR images (700/15) obtained in a 71-year-old man with skin cancer, who had TMJ tenderness and discomfort in the left ear. Symptoms related to V₃ developed 8 months later.

A, Axial image shows a parotid gland mass (T) that extends medially along the expected course of the auriculotemporal nerve (arrowheads) into the parapharyngeal space.

B and C, Coronal images show the superior extension of the tumor along V₃ (arrows in B) and middle meningeal artery (arrows in C) to involve the intracranial structures. Subtle dural enhancement is seen along the floor of the temporal fossa on the left (arrowheads in C). Note the normal appearance of V₃ on the right. T indicates tumor. Image in C is slightly posterior to the image in B.

MR images obtained in a 70-year-old man with skin cancer who had progressive right facial nerve weakness. Cross-sectional CT (not shown) and MR imaging were performed to evaluate the patient’s facial weakness and preauricular pain.

A, Axial nonenhanced T1-weighted image (600/14) shows a subtle area of soft tissue (arrowheads) posterior and medial to the ramus of the mandible (R) on the right side that is abnormal when compared with the left.

B, Gadolinium-enhanced fat-suppressed T1-weighted image (500/14) obtained at the same level as in A shows marked enhancement of the area of abnormal soft tissue (arrowheads) in A. This finding was interpreted as normal at an outside institution.

C, Repeat nonenhanced T1-weighted image (600/14) obtained 12 months after the first MR examination shows the extensive progression of the tumor (arrows), with now obvious infiltration of the parapharyngeal space on the right.

D and E, Coronal (D) and axial (E) contrast-agent–enhanced T1-weighted images (600/14) show the growth of the tumor along V₃ (arrowheads in D) into the Meckle cave (solid arrow in E) and cavernous sinus (arrowheads in E). Note the normal appearance of the Meckle cave on the left side (open arrow in E).

Drawings depict the relationship between the mandibular division of the trigeminal nerve (V), auriculotemporal nerve, facial nerve, and the maxillary artery (ma) and its branches. The auriculotemporal nerve arises from V₃ from two roots (thin arrows). The middle meningeal artery (thick arrow) courses between the two rootlets, which coalesce, just posterior to the artery, to form a short trunk (★ in B). The trunk forms multiple branches with the anterior and posterior communicating rami (arrowheads), joining the facial nerve (★) within the parotid gland.

A, Coronal projection. aa indicates the anterior auricular nerve; iam, inferior nerve to the external acoustic meatus; sam, superior nerve to the external acoustic meatus; sta, superficial temporal artery; and str, superficial temporal ramus.

B, Axial projection. R indicates the mandibular ramus.