Detecting and defining the anatomic extent of large nerve perineural spread of malignancy: comparing "targeted" MRI with the histologic findings following surgery.

Abstract

The accurate preoperative identification of the extent of perineural spread (PNS) of malignancy along a cranial nerve is vital to the design of an appropriate surgical resection. Our purpose was to determine the sensitivity of targeted MRI in predicting the presence of disease and the anatomic extent of spread when compared with histologic findings. A retrospective review was performed of 25 patients with PNS who had targeted MRI and surgery to excise perineural tumor (2002-2008). MRI detected PNS in 30 of 30 nerves (100%) with 1 false positive. MRI correctly identified the extent of spread based on histology in 25 of 30 nerves (83.3%). In 4 of 30 cases (13.3%) MRI underestimated the extent of spread proximal to the Gasserian ganglion that, if diagnosed preoperatively, may have deemed the patient inoperable. MRI demonstrated the presence and anatomic extent of PNS in the majority of cases. MRI may underestimate microscopic spread proximal to the Gasserian ganglion.