Visualization of the trochlear nerve in the cistern with use of high-resolution turbo spin-echo multisection motion-sensitized driven equilibrium

Abstract

BACKGROUND AND PURPOSE: The trochlear nerve is so thin that it is rarely observed with MR imaging. Therefore, we used highresolution MSDE to reliably visualize the cisternal segments of the trochlear nerve. MATERIALS AND METHODS: Participants were 10 healthy young adults (mean age, 24 years), and 20 trochlear nerves were examined. HR-MRC, BS-MRC, and HR-MSDE were performed. A neuroradiologist judged the visibility of the trochlear nerves as 1 of 4 grades ("Excellent," "Good," "Fair," and "Not") in each MR imaging sequence. The findings were then statistically analyzed with the χ2 test. RESULTS: Of all 20 trochlear nerves, 6 with HR-MRC, 13 with BS-MRC, and 18 with HR-MSDE were judged as "Excellent." CSF flow-related artifacts and vessels in the cistern and cerebellar tentorium in HR-MRC tended to prevent the neuroradiologists from identifying the trochlear nerve. Vessels in the cistern and cerebellar tentorium in BS-MRC also tended to prevent the neuroradiologists from identifying the trochlear nerve. Compared with other sequences, HR-MSDE visualized the trochlear nerve more often. The χ2 test revealed statistically significant differences among the 3MR imaging sequences (P>.01). The scan time of HR-MSDE was approximately 1.5-2.2 times longer than that of the other sequences. CONCLUSIONS: HR-MSDE is able to clearly visualize the trochlear nerve and has the same or better ability to delineate the trochlear nerve compared with other MR imaging sequences, though its long scan time does not yet yield practical use.