Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder affecting the upper and lower motor neurons causing progressive weakness. It eventually involves the diaphragm which leads to respiratory paralysis and subsequently death. Phrenic nerve (PN) conduction studies and diaphragm ultrasound has been studied and correlated with pulmonary function tests in ALS patients. However, PN ultrasonography has not been employed in ALS. This study aims to sonographically evaluate the morphologic appearance of the PN of ALS patients. Thirty-eight ALS patients and 28 normal controls referred to the neurophysiology laboratory of two institutions were retrospectively included in the study. Baseline demographic and clinical variables such as disease duration, ALS Functional Rating Scale-Revised score, and ALS region of onset were collected. Ultrasound was used to evaluate the PN cross-sectional area (CSA) of ALS and control subjects. The mean PN CSA of ALS patients were 1.08 ± 0.39 mm on the right and 1.02 ± 0.34 mm on the left. The PN CSA of ALS patients were significantly decreased compared to controls (p value < 0.00001). The PN CSA of ALS patients was not correlated to any of the demographic and clinical parameters tested. This study demonstrates that ALS patients have a smaller PN size compared to controls using ultrasonography.
Highlights
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder predominantly affecting the upper and lower motor neurons causing progressive weakness and muscle wasting [1]
To demonstrate in vivo changes, this study aims to determine if a pure motor nerve such as the phrenic nerve would sonographically show evidence of decreased nerve caliber similar to other peripheral nerves in ALS patients
It can be noted that age, disease duration and ALSFRS-R scores have F-statistic values less than 5, which is considered very low, the authors believe that these have little relationship with Phrenic nerve (PN) cross-sectional area (CSA) measurements
Summary
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder predominantly affecting the upper and lower motor neurons causing progressive weakness and muscle wasting [1]. As a surrogate marker for respiratory function, diaphragm ultrasound has been employed in ALS in several studies [3,4,5,6]. Diaphragm thickness was observed to be reduced in ALS and it is correlated with measures of respiratory function [2,3,4,5]. Phrenic nerve (PN) motor conduction studies have been used to evaluate the respiratory function and have been observed to detect latent respiratory dysfunction as well as predict survival in ALS [7, 8]. Peripheral nerve ultrasound has been investigated in ALS for diagnostic and monitoring purposes [2]. No consensus has yet been achieved as to which nerves are specific and sensitive for ALS diagnosis and disease progression monitoring [2]
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