BACKGROUND: High-resolution 3-dimensional (3-D) magnetic resonance imaging (MRI) is widely used to predict the neurovascular anatomy within the cerebellopontine angle.
OBJECTIVE: To assess the value of 3-D steady-state free precession imaging (SSFP) and time-of-flight magnetic resonance angiography (TOF MRA) in detecting the offending vessels in hemifacial spasm in comparison to intraoperative endoscopic visualization.
METHODS: 42 patients underwent endoscope-assisted microvascular decompression (MVD). All available preoperative 3-D SSFP and TOF MRA images were checked. Intraoperative videos were captured by a high-definition endoscopic camera attached to endoscopes while exploring the area of facial nerve root exit zone (REZ). Evaluation of the 3-D images was performed by 2 independent groups of observers and compared with the operative findings.
RESULTS: Three-D MRI had an average positive predictive value (PPV) of 89.1% in differentiating between simple and complex compression. Mean accuracy of the images in detection of the offending vessels was 83.3% and 77% according to the first and second groups of observers, respectively. Averaged inter-observer agreement between the 2 groups of observers was substantial, with an averaged Kappa coefficient (K) of 0.56. In the simple compression group, mean accuracy was 97% and 89.4% according to the first and second groups of observers, respectively. Averaged K for agreement was substantial (K = 0.65).
CONCLUSION: According to endoscopic visualization, 3-D SSFP and TOF MRA images are accurate in detecting the offending vessels in simple compression of the facial nerve, and in predicting presence of a complex compression with variable sensitivity in identifying all offending vessels.
ABBREVIATIONS: 3-D, 3-dimensional
AICA, Anterior inferior cerebellar artery
BA, Basilar artery
BAEPS, Brainstem auditory evoked potentials
CI, Confidence interval
CISS, Constructive interference in steady state
FIESTA, Fast imaging employing steady state acquisition
K, Kappa coefficient
MVD, Microvascular decompression
PICA, Posterior inferior cerebellar artery
PPV, Positive predictive value
REZ, Root exit zone
SSFP, Steady-state free precession imaging
T2w, T2 weighted
VA, Vertebral artery