Differentiation between schwannoma of the vagus nerve and schwannoma of the cervical sympathetic chain by imaging diagnosis.

Ultrasonography, computed tomography, and magnetic resonance imaging were performed to differentiate preoperatively between schwannomas of the vagus nerve and schwannomas of the cervical sympathetic chain by observing the position of schwannomas in regard to the surrounding blood vessels. Ultrasonography also permitted direct visualization of the vagus nerve, so its position relative to the schwannoma could be examined. In schwannomas of the vagus nerve the schwannoma grew between the common carotid artery and the internal jugular vein or between the internal carotid artery and the internal jugular vein, resulting in an increase in the distance between the artery and vein (separation). In schwannomas of the cervical sympathetic chain, no separation was observed between the internal jugular vein and the common carotid artery or internal carotid artery. Ultrasonography with a 7.5-MHz transducer showed the derivation of the tumor from the vagus nerve in schwannomas of the vagus nerve but showed the vagus nerve on the tumor surface in schwannomas of the cervical sympathetic chain.