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

Abstract

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.

Keywords: amyotrophic lateral sclerosis; cochlear nerve; facial nerve; fast imaging employing steady-state acquisition.