Science News: Nerve Ultrasound in Friedreich’s Ataxia: Enlarged Nerves as a Biomarker of Disease Severity

Published July 22, 2024

Science News

Submitted by: Eman Tawfik, MD
Edited by: Rebecca O'Bryan, MD

Citation: Di Pietro G, Cioffi E, Falco P, et al. Nerve ultrasound in Friedreich's Ataxia: enlarged nerves as a biomarker of disease severity. Clin Neurophysiol. 2024;159:75-80. doi:10.1016/j.clinph.2024.01.004

Summary: Friedreich’s ataxia affects the central and peripheral nervous systems, as well as other systems. There is a continuous search for effective treatment. Therefore, finding a reliable disease biomarker is needed. 

Sensory neuropathy is one of the disease hallmarks. Nerve conduction studies (NCSs) are typically used to detect neuropathy but is not the optimum biomarker because sensory responses are commonly lost. Therefore, the authors in this study assessed the ability of nerve ultrasound (US) to serve as a potential biomarker in patients with Friedreich’s ataxia.

The authors prospectively recruited patients who were genetically confirmed to have Friedreich’s ataxia.

Motor NCS of the median, ulnar, tibial, and peroneal nerves and sensory NCS of the median, ulnar, superficial radial, and sural nerves were performed for all patients. The median, ulnar, tibial, peroneal, and sural nerves were scanned along their entire course and the nerve cross-sectional area (CSA) was measured at pre-determined levels. The total number of abnormal sites was determined after exclusion of the common entrapment sites.

There were 10 patients with Friedreich’s Ataxia and 20 healthy controls included. Nine patients had lost sensory responses and one patient had reduced amplitude of the sensory responses in NCS. The motor NCS were completely normal.

Significant enlargement of the median and ulnar nerves at the axilla and arm was found in the patients group compared to the controls. The total number of abnormal nerve sites positively correlated with the Scale for the Assessment and Rating of Ataxia (SARA), Friedreich’s Ataxia Rating Scale (FARS), modified FARS (mFARS), the Inflammatory Neuropathy Cause and Treatment Disability Score (INCAT), and the Activities of Daily Living (ADL 0-36 score), but inversely correlated with the Instrumental Activities of Daily Living (IADL).

The correlation between nerve US abnormalities and the clinical disability scales denotes a potential role of nerve US as a biomarker for disease severity and treatment effects.  

Comments: This is an interesting study addressing the potential role of nerve US as a biomarker for Friedreich’s ataxia. The good point is that the authors followed a standard scanning protocol, assessed multiple nerves, and scanned them along their entire courses. The limitations include small sample size and the lack of assessment of other sonographic parameters like nerve echogenicity and vascularity. Nerve US has become an important assessment tool in many NM disorders. Knowledge of its possible utilities help its integration in clinical practice.

Article of similar interest: Mulroy E, Pelosi L, Leadbetter R, et al. Peripheral nerve ultrasound in Friedreich ataxia. Muscle Nerve. 2018;57(5):852-856. doi:10.1002/mus.26012