Sensory neuropathy as part of the cerebellar ataxia neuropathy vestibular areflexia syndrome

Abstract

Objective: The syndrome of cerebellar ataxia with bilateral vestibulopathy was delineated in 2004. Sensory neuropathy was mentioned in 3 of the 4 patients described. We aimed to characterize and estimate the frequency of neuropathy in this condition, and determine its typical MRI features.

Methods: Retrospective review of 18 subjects (including 4 from the original description) who met the criteria for bilateral vestibulopathy with cerebellar ataxia.

Results: The reported age at onset range was 39-71 years, and symptom duration was 3-38 years. The syndrome was identified in one sibling pair, suggesting that this may be a late-onset recessive disorder, although the other 16 cases were apparently sporadic. All 18 had sensory neuropathy with absent sensory nerve action potentials, although this was not apparent clinically in 2, and the presence of neuropathy was not a selection criterion. In 5, the loss of pinprick sensation was virtually global, mimicking a neuronopathy. However, findings in the other 11 with clinically manifest neuropathy suggested a length-dependent neuropathy. MRI scans showed cerebellar atrophy in 16, involving anterior and dorsal vermis, and hemispheric crus I, while 2 were normal. The inferior vermis and brainstem were spared.

Conclusions: Sensory neuropathy is an integral component of this syndrome. It may result in severe sensory loss, which contributes significantly to the disability. The MRI changes are nonspecific, but, coupled with loss of sensory nerve action potentials, may aid diagnosis. We propose a new name for the condition: cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS).

Figures

Figure 1. Homunculus demonstrating the pattern of sensory neuropathy

The sensory modality represented is pinprick. Density of shading relates to the number of subjects demonstrating a sensory deficit in that anatomic region. It can be seen that some subjects have global loss, suggesting a neuronopathy, but that this probably represents extreme length-dependent loss.

Figure 2. T1-weighted MRI illustrating the spectrum of cerebellar atrophy found in the cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS)

(A) Sagittal view of very mild cerebellar atrophy; (B) parasagittal view of very mild cerebellar atrophy; (C) sagittal view of very mild cerebellar atrophy; (D) parasagittal view of very mild cerebellar atrophy; (E) sagittal view of mild cerebellar atrophy; (F) parasagittal view of mild cerebellar atrophy; (G) sagittal view of moderate cerebellar atrophy; (H) parasagittal view of moderate cerebellar atrophy; (I) sagittal view of non-CANVAS pattern cerebellar atrophy for comparison; (J) parasagittal view of non-CANVAS pattern cerebellar atrophy for comparison; (K) parasagittal view of the labeled cerebellar lobules, and crus I and II; (L) sagittal view of the labeled cerebellar lobules.