Respiratory and bulbar dysfunctions in amyotrophic lateral sclerosis: electrophysiologic and muscle ultrasound assessment

Abstract Background The main causes of death in amyotrophic lateral sclerosis (ALS) are respiratory and bulbar dysfunctions. Phrenic nerve conduction studies and diaphragm ultrasound can be used to assess the diaphragmatic function which is the primary muscle of respiration. Furthermore, the bulbar function can be assessed by the tongue ultrasound. The study included eleven patients with definite ALS; 8 males and 3 females with mean age of 44.55 ± 8.90 years. All patients were subjected to phrenic nerve conduction studies, ultrasound of the diaphragm and ultrasound examination of the tongue. Results In 54.4% of the patients, the phrenic nerve compound motor action potential (CMAP) amplitude was reduced. All patients had a normal respiratory thickening ratio, although 9.09% of the patients had abnormal diaphragmatic excursion. This revealed a statistically significant difference (p value = 0.022) between diaphragm ultrasound and phrenic nerve amplitude. The revised ALS functional rating scale (ALSFRS-R) respiratory sub-score and the phrenic nerve amplitude had a significant correlation ( p = 0.007), although diaphragm ultrasound did not. The sensitivity for tongue echo intensity was 63.6%. Conclusion Our study showed that the diaphragm ultrasound was inferior to phrenic nerve amplitude in assessment of respiratory functions. Tongue echo intensity could be an adjuvant tool in assessment of bulbar functions in addition to other more sensitive methods.