Correlation between electromyographic reflex and MR imaging examinations of the trigeminal nerve

BACKGROUND AND PURPOSE: Previous studies have shown that clinical localizat ion of trigeminal nerve lesions is inaccurate as compared,vith MR imaging f indings, The purpose of our study was to ascertain the added value of elect romyographic (EMG) investigation of the trigeminal nerve reflexes for the i mprovement of lesion localization and for the preselection of patients for MR imaging, METHODS: We reviewed the EMG studies of the trigeminal reflexes and the MR imaging studies of 20 patients with unilateral symptoms and signs related t o the trigeminal nerve (40 trigeminal nerves examined), The results of the two studies were compared to assess the value of EMG in predicting MR imagi ng outcome. Lesion localization as demonstrated by EMG was compared with lo calization at MR imaging. MR imaging was used as the standard of reference. RESULTS: Eight (40%) of 20 patients had MR imaging findings related to pres enting trigeminal symptoms, including five brain stem lesions and three per ipheral lesions. Fourteen (70%) of 20 patients had EMG abnormalities relate d to presenting symptoms and signs. For brain stem lesions, lesion localiza tion as shown by EMG corresponded well with MR imaging findings. EMG yielde d a sensitivity of 100%, a specificity of 81%, a positive predictive value of 57%, and a negative predictive value of 100% in predicting MR imaging re sults. Interobserver agreement was good for both the EMG reflex and MR imag ing examinations. CONCLUSION: Our data suggest that EMG recordings of the trigeminal reflexes can be used to exclude structural lesions in patients with symptoms relate d to the trigeminal nerve, When a lesion is localized in the brain stem wit h EMG, a tailored MR imaging examination of this region may be sufficient.