Facial nerve atrophy in patients with amyotrophic lateral sclerosis: Evaluation with fast imaging employing steady‐state acquisition (FIESTA)

Background In amyotrophic lateral sclerosis (ALS), motor neurons in the brainstem markedly deplete, whereas sensory neurons are less severely affected. Purpose To determine whether facial nerve (FN) measurement on 3D fast imaging employing steady‐state acquisition (FIESTA) is useful for ALS diagnosis. Study Type Retrospective. Subjects Fifteen ALS patients and 16 controls. Field Strength/Sequence 3T FIESTA MR. Assessment The cross‐sectional area of the FN and cochlear nerve (CN) were measured, and the FN/CN ratio (FCR) was assessed. For qualitative assessment, the FN cross‐sectional area was compared with that of the CN and the following scores were assigned: score 1 (large), the FN is larger than the CN; score 2 (almost equal), the size difference between the FN and CN is within 10%; score 3 (small), the FN is smaller than the CN (10–50%); score 4 (significantly small), size of the FN is less than half the size of the CN. Statistical Tests The differences in FCR between the ALS patients and the controls were tested using the Wilcoxon Mann–Whitney U ‐test. For the qualitative and quantitative assessments, we performed a receiver operating characteristic analysis for the diagnosis of ALS with an abnormal finding as score 3 or 4. Results The mean FCR was significantly smaller for ALS patients (0.71 ± 0.17) than for controls (0.95 ± 0.08) ( P < 0.001) and the area under the curve was 0.93. When an FN score was 3 or 4, indicative of FN atrophy, the sensitivity and specificity values of FIESTA for discriminating ALS patients from controls were 93.3% (14/15) and 90.0% (18/20), respectively. Data Conclusion The FN atrophy revealed on FIESTA, which may reflect lower motor neuron impairment in ALS, allowed us to distinguish ALS patients from controls with a high degree of accuracy. Level of Evidence: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:757–766.