Friedreich Ataxia Nerve Ultrasund

"Friedreich ataxia is the most common inherited autosomal recessive ataxia. It is caused by a GAA repeat expansion in the frataxin gene on chromosome 9q21.11. Symptoms usually begin in childhood, typically between 9 and 13 years of age. The disease leads to progressive damage of the nervous system and the heart, as well as multisystem involvement of various degrees, leading to diabetes, vision and hearing loss and scoliosis. Over time, most patients lose the ability to walk and require a wheelchair, often by their mid-twenties. The severity and progression of the disease can vary depending on various factors such as the age at onset and the size of the GAA triplet expansion.

Traditionally, Friedreich ataxia has been considered a disorder primarily affecting nerve cells, also called neuronopathy. However, recent studies using ultrasound imaging of peripheral nerves have shown that some nerves may appear enlarged, particularly in the upper limbs. This is in contrast with findings usually observed in other neuronopathies, where peripheral nerves tend to become thinner.

The aim of this study is to use nerve ultrasound to better understand changes in intraneural vascularization and nerve in patients with Friedreich ataxia. In particular, we assess the presence of intraneural blood flow within the nerves using a high-resolution ultrasound technique.

The study includes 13 patients with genetically confirmed Friedreich ataxia who are followed at the Neurogenetics Competence Center of Nice University Hospital. Ultrasound examinations are performed on the median and ulnar nerves at standardized locations: for median nerve at wrist, forearm (10 cm from the distal wrist crease), antecubital fossa, mid-arm and axilla; for ulnar nerve at the wrist, forearm (10 cm from the pisiform bone), at the elbow (5 cm below and above the elbow), mid-arm and axilla; the brachial plexus is measured at level C5, C6, C7.

In addition to vascularization, we also measure nerve size (cross-sectional area) and evaluate internal nerve structure.

This study aims to improve understanding of nerve involvement in Friedreich ataxia and to explore whether ultrasound could provide useful markers of disease severity."