Lower limb nerve ultrasound: A four‐way comparison of acquired and inherited axonopathy, inherited neuronopathy and healthy controls

Introduction/Aims In a recent study, we showed that nerve ultrasound of the upper limbs could distinguish inherited sensory neuronopathy from inherited axonopathy; surprisingly, no differences were found in the lower limb nerves. In this study, we compared lower limb nerve ultrasound measurements in inherited neuronopathy, inherited axonopathy, and acquired axonopathy. Methods Tibial and sural nerve ultrasound cross‐sectional areas (CSAs) of 34 healthy controls were retrospectively compared with those of three patient groups: 17 with cerebellar ataxia with neuronopathy and vestibular areflexia syndrome (CANVAS), 18 with Charcot‐Marie‐Tooth type 2 (CMT2), and 18 with acquired length‐dependent sensorimotor axonal neuropathy, using ANOVA with post‐hoc Tukey honestly significance difference (HSD) (significance level set at p < .05). Results The nerve CSAs of CANVAS and CMT2 patients were not significantly different. Both the tibial and the sural nerve CSAs were significantly smaller in CANVAS and CMT2 compared with the acquired axonal neuropathy group. Tibial nerve CSAs of CANVAS and CMT2 were significantly smaller than controls. Tibial and sural nerve CSAs of the acquired axonal neuropathy group were also significantly larger than the controls'. Discussion Ultrasound of the lower limb nerves distinguished inherited from acquired axonopathy with the nerve size respectively reduced and increased in these two groups. This has potential implication for the differential diagnosis of these diseases in clinical practice.