O-23 Cervical muscle weakness correlates with respiratory function in Amyotrophic Lateral Sclerosis

Abstract

Background In Amyotrophic Lateral Sclerosis (ALS) weak cervical muscles are commonly found. These accessory muscles of respiration are innervated by medially spinal-located motor neurons close to phrenic nerve nuclei. A correlation between cervical strength and prognosis has been described. We investigate the association with respiratory function. Methods Consecutive ALS patients assessed with flexor/extensor cervical muscle strength, revised functional ALS rating scale (ALSFRS-R), phrenic nerve studies and forced vital capacity (FVC) within 3 months were included. Flexor/extensor strength were assessed respectively in dorsal decubitus/sitting and categorized as normal/abnormal (MRC = 5/MRC Results We included 281 patients (157 men, disease duration 16.216 months; meanFVC 80.424%; MeanPhrenAmpl 0.50.25 m). Weak cervical flexion/extension: 156/59 patients. Abnormal PhrenAmpl: 100 patients; Abnormal FVC: 45; Abnormal RofALSFRS-R: 108. Sensitivity, specificity, PPV, NPP of extensor muscles for PhrenAmpl, FVC and RofALSFRS-R: 31%-35.5%, 84.5%-85.2, 33.3–52.5%, 66.1%-86.1%, respectively. Sensitivity, specificity, PPV, NPP of flexor muscles for PhrenAmpl, FVC and RofALSFRS-R: 66.6%-73.3%, 51.5%-54.1%, 24.4%-46.8%, 70.7%-90.1%, respectively. Combined flexor/extensor sensitivity, specificity, PPV, NPP: 68.5%-77.7%, 48.5%-51.4%, 26%-46%, 70%-91.2%, respectively. AUC: 0.58–0.64. Conclusion Weak cervical muscles indicate higher probability of respiratory involvement. Weak extensors are a strong predictor (high specificity) of respiratory compromise in ALS, which should be regarded as a significant warning in clinical practice.