Objectives Patients with cerebellar ataxia neuropathy vestibular areflexia syndrome (CANVAS) have sensory impairment due to dorsal root ganglionopathy. After preliminary findings of small nerves on ultrasound in CANVAS, we sought to systematically study a larger cohort of CANVAS patients to see if this is a feature of this ganglionopathy and thus distinct from the ultrasound findings in axonal neuropathy.
Methods The ultrasound cross sectional area (CSA) of median and ulnar nerves of 14 CANVAS patients was compared with 14 age- and gender-matched healthy controls (HC) and 14 age-and gender-matched patients with acquired axonal neuropathy (AxPN). The individual CSAs of CANVAS and AxPN patients were also compared with the mean CSA of our reference population.
Results The nerve CSA of CANVAS patients was significantly smaller than the CSA of both HC and AxPN at all sites (p<0.00001). By contrast, the CSA of AxPN was mildly larger than the HC CSA at all sites (p<0.05). All but one individual measurement of CSA at mid-forearm level in the CANVAS patients fell outside the normal control range and was >2 SDs below a reference mean.
Conclusions The small nerves in CANVAS probably reflect nerve thinning from axonal loss secondary to ganglion cell loss. This is in contradistinction to the ultrasound abnormality in AxNP, in which the nerves are mildly enlarged. Our data show a role for ultrasound in the diagnosis of CANVAS ganglionopathy. This may also be applicable to ganglionopathy from other causes.
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