# Examination of the Peripheral Nervous System in Children With Spinal Muscular Atrophy: A High‐Resolution Ultrasonographic Study

## TL;DR

This study uses high-resolution ultrasound to examine nerve structure in children with spinal muscular atrophy, finding smaller nerve sizes and altered appearances compared to healthy children.

## Contribution

The study demonstrates the usefulness of HRUS for monitoring peripheral nerve changes in children with SMA.

## Key findings

- Children with SMA had smaller median nerve cross-sectional areas compared to controls.
- HRUS revealed a loss of fascicular nerve structure in SMA children, linked to muscle atrophy.
- Nerve growth in SMA children can be modeled with a logarithmic curve similar to healthy children.

## Abstract

Recent studies have shown that high‐resolution ultrasound (HRUS) devices allow us to accurately measure peripheral nerves in newborns. In consideration of these developments, this study aimed to analyze the structure and cross‐sectional area (CSA) of the median nerve in children with SMA and evaluate the usefulness and reproducibility of HRUS imaging for the monitoring of peripheral nerves in these children.

A total of 12 participants aged 1–15 years with SMA were included in this repeated cross‐sectional study. In addition, 97 normally developing children aged 2 days to 17 years were included as controls. Using HRUS devices, the structure and CSA of the median nerve were determined at three sites (wrist, forearm, and above the elbow). The measured CSA and nerve structure were compared between the groups.

The CSA of the median nerve was smaller in the children with SMA than in the controls. Compared to the controls, SMA children had a mean CSA ranging from 0.70 to 1.02 mm2 smaller while adjusting for age. Similar to normally developing children, the increase in CSA with age in children with SMA can be described using a logarithmic curve. Furthermore, ultrasonographic examination indicated a loss of the fascicular structure of the nerves, which, together with muscle atrophy, led to an altered sonographic appearance and more difficult visualization.

HRUS is a useful method for monitoring nerve growth in children with SMA.

This study aimed to analyze the structure and cross‐sectional area (CSA) of the median nerve in children with spinal muscular atrophy (SMA) and evaluate the usefulness of high‐resolution ultrasound (HRUS) imaging for the monitoring of peripheral nerves in these children. A total of 12 children with SMA and 97 normally developing children were included in this repeated cross‐sectional study. The mean CSA of the median nerve, while adjusting for age, was smaller in the children with SMA (dots) than in the controls (red trend line). Furthermore, ultrasonographic examination indicated a loss of the fascicular structure of the nerves, which, together with muscle atrophy, led to an altered sonographic appearance. Repeated measurements demonstrated that HRUS is a useful method for monitoring nerve growth in children with SMA.