Nerve Ultrasound in Patients With Friedreich Ataxia

Nerve enlargement has been reported in patients with Friedreich ataxia (FRDA). The underlying cause remains unclear, and both inflammatory processes and dysmyelination have been suggested as potential mechanisms. This study was aimed at assessing nerve morphology with high-resolution ultrasound, to identify and describe patterns of nerve pathology.

Patients with genetically confirmed FRDA were included, clinically examined, and assessed with high-resolution ultrasound. Cross-sectional area measurements were compared with previously published normal values.

Among 20 included patients, ultrasound abnormalities were found in 17 (85%). Nerve enlargement of the median and/or ulnar nerve in the proximal nerve segments was observed in 45% of patients and was statistically significant compared to published normal values. Lower extremity nerve enlargement was observed in 20% of patients. Eight patients did not show any nerve enlargement. Diminished cross-sectional area, indicative of nerve atrophy, was present, particularly in the distal segments of the ulnar nerve (in 25% of patients, p < 0.05) and the tibial nerve (popliteal fossa in 30% of patients, medial malleolus in 30% of patients, both p < 0.05). Nerve enlargement showed no significant correlations with disease severity or age of disease onset.

Peripheral nerve morphology in FRDA is variable and includes not only nerve enlargement but also nerve atrophy, thus reflecting complex segmental pathology beyond axonal degeneration.