PERINEURAL TUMOR EXTENSION ALONG THE TRIGEMINAL NERVE - MAGNETIC-RESONANCE-IMAGING FINDINGS

Objective: To evaluate the magnetic resonance imaging (MRT) findings o f 15 patients with perineural tumor extension along the trigeminal ner ve in correlation with clinical data. Methods. The clinical records an d MRI studies of 15 patients with perineural tumor extension along the trigeminal nerve were retrospectively reviewed. Imaging studies inclu ded plain and contrast-enhanced thin section T1-weighted spin echo (T1 -WSE) MRI with and without fat-suppression. The studies were compared to determine which sequence provided greatest tumor conspicuity and be st depiction of tumor extent. The conspicuity of these tumors was asse ssed on the available sequences by two observers by consensus. Results : The contrast-enhanced T1-weighted spin echo fat-suppressed images (T 1-WSECEFS) demonstrated greatest tumor conspicuity and best depiction of tumor extent in the extracranial head and neck and skull base regio n. The conventional T1-weighted spin echo pre- and postcontrast images were, however, diagnostic of perineural tumor extension in 11 patient s due to the presence of considerable tumor bulk and extension well ab ove the skull base. In the other four patients the perineural tumor wa s poorly visualized on the conventional T1-WSE images and well visuali zed on the fat-suppressed images. The mandibular division of the trige minal nerve (V3) was most commonly involved (n = 10), followed by the maxillary (V2; n = 5) and ophthalmic (V1; n = 2) division. Two patient s had both mandibular as well as maxillary nerve involvement. The find ing of perineural tumor extension had significant impact on patient ma nagement: based on the MR imaging study, the primary tumor was conside red inoperable (n = 13), the extent of surgery was expanded (n = 2) an d radiation therapy (RT) ports were extended (n = 12). Conclusion: Com plete trigeminal nerve imaging is recommended when evaluating (suspect ed) head and neck malignancies with a high risk for perineural extensi on. In these cases thin section axial and coronal precontrast T1-WSE M R images and postcontrast T1-WSE MR images with fat-suppression should be obtained. In the rare event that artifacts degrade the quality of the fat-suppressed images, contrast-enhanced T1-WSE sequences without fat-suppression can additionally be used. (C) 1997 Elsevier Science Ir eland Ltd.