Perineural invasion of the trigeminal nerve in patients with nasopharyngeal carcinoma: Imaging and clinical correlations

BACKGROUND. A nasopharyngeal carcinoma (NPC) arising from the fossa of Rosenmuller frequently extends to the paranasopharyngeal space. The common clinical manifestations are neck masses, ear symptoms, bloody nasal discharge, and cranial nerve palsy. Among the patients with cranial nerve palsy, trigeminal neuropathy is one of the most observable neurologic manifestations. This study was designed to evaluate trigeminal perineural tumor invasion. METHODS. One hundred and ten patients with newly diagnosed NPC were studied. Both computed tomography and magnetic resonance imaging of the head and neck, including the nasopharynx, were performed during the same visit. The extent of the trigeminal perineural tumor invasion was evaluated and correlated with neurologic symptoms. RESULTS. At the time of diagnosis, facial pain or paresthesia was noted in 23.6% (26 of 110) of the patients. However, 53.6% (59 of 110) of the patients radiologically had demonstrable trigeminal perineural tumor invasion. Perineural invasion of the extracranial portion of the mandibular division (V3) frequently occurred when an NPC encroached on the paranasopharyngeal region. Nevertheless, the patients usually did not have any subjective sensory impairment. Perineural invasion of the intracranial segment of the mandibular and maxillary divisions (V2) might occur when an NPC spread along the V3 through the foramen ovale. The majority of the patients who had tumor invasion of the intracranial paracavernous region suffered from facial pain or paresthesia over the distribution of the V2 and/or V3. Sensory impairment of the opthalmic division was less common. CONCLUSIONS. These findings suggest that patients can tolerate perineural infiltration of the extracranial segment of the trigeminal nerve by NPC in the early stage of the disease when the tumor is still confined beneath the base of the skull. Dysfunction of the trigeminal nerve is closely related to perineural tumor invasion of the intracranial segment.