CT and MRI evaluation of nerve sheath tumors of the cervical vagus nerve.

Objective: Nerve sheath tumors arising from the cervical vagus are rare. The purpose of this study was to evaluate the role of CT and MRI in the diagnosis of these uncommon neoplasms.

Materials And Methods: The CT and MR studies and clinical data of 11 patients with surgicopathologic evidence of a nerve sheath tumor of the cervical vagus (nine schwannomas [including two ancient schwannomas] and two neurofibromas) who had been referred to our institute from January 1999 through 2009 were retrospectively reviewed. The tumors were evaluated with respect to their location, number, morphology, attenuation and/or signal intensity, enhancement characteristics, and patterns of mass effect.

Results: The tumors were solitary and well circumscribed. On CT, eight tumors were hypodense with poor enhancement, two were predominantly isodense, and a single lesion had multiple cystic areas with enhancing solid components. On MRI, they were heterogeneously bright on T2-weighted images with intense, inhomogeneous postgadolinium enhancement. The "split fat" sign, "entering and exiting nerve" sign, "fascicular" sign, and "hyperintense rim" sign were seen in some patients. The internal or common carotid artery was displaced anteriorly in eight patients, maintained a neutral position in two patients, and was displaced posterolaterally in another patient. In all patients except two, the tumor separated the carotid artery from the internal jugular vein. Vagal schwannomas splayed the carotid bifurcation in three patients.

Conclusion: In conclusion, we present the patterns of mass effect and a spectrum of CT and MRI characteristics of nerve sheath tumor of the cervical vagus including observations that are sparingly described in the published literature.