Imaging Features of Intracranial Invasion of Nasopharyngeal Carcinoma via the Carotid Canal

Intracranial spread of nasopharyngeal carcinoma most commonly occurs directly through the floor of the middle cranial fossa or perineurally along the mandibular or maxillary branches of the trigeminal nerve. Failure to detect nasopharyngeal carcinoma spread superiorly through the carotid canal may result in a disease staging that is too low and, therefore, insufficient treatment. We retrospectively reviewed the imaging of 7 patients with nasopharyngeal carcinoma with carotid canal extension to determine the characteristic features of this pattern of intracranial spread. Findings included the following: posterior extension of nasopharyngeal carcinoma to the carotid space, tumor tissue surrounding the internal carotid artery with loss of the normal fat, mild osseous widening of the carotid canal, enhancement within the canal, narrowing of the petrous or cavernous ICA segments, and a convex lateral cavernous sinus wall. Although intracranial spread of nasopharyngeal carcinoma superiorly from the skull base to the cavernous sinus via the carotid canal has been reported in passing, it lacked the description of the imaging findings for diagnosis described in this article. In one of the patients without further intracranial involvement, these findings were the sole means for the correct staging. Radiographic evaluation of nasopharyngeal carcinoma should, therefore, include scrutiny of the carotid canal.