Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS): a review of the clinical features and video‐oculographic diagnosis

Abstract

The association of bilateral vestibulopathy with cerebellar ataxia was first reported in 1991 and delineated as a distinct syndrome with a characteristic and measurable clinical sign--an absent visually enhanced vestibulo-ocular reflex--in 2004. We reviewed 27 patients with this syndrome and show that a non-length-dependent sensory deficit with absent sensory nerve action potentials is an integral component of this syndrome, which we now call "cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome" (CANVAS). All patients had brain MRI and 22/27 had evidence of cerebellar atrophy involving anterior and dorsal vermis, as well as the hemispheric crus I. Brain and temporal bone pathology in one patient showed marked loss of Purkinje cells and of vestibular, trigeminal, and facial ganglion cells, but not of spiral ganglion cells. There are two sets of sibling pairs, suggesting CANVAS is a late-onset recessive disorder. The characteristic clinical sign-the visual vestibulo-ocular reflex deficit-can be demonstrated and measured clinically using video-oculography.

Bilateral Vestibular Hypofunction: Challenges in Establishing the Diagnosis in Adults

“…magnetic resonance imaging, computed tomography), lumbar puncture, sensory nerve action potentials, speech assessment, etc. [18,19,20,23,40,89]. However, these tests are mainly used for determination of coexisting problems or the etiology of BVH (table 1), not for an evaluation of vestibular function.…”

“…Vestibular disorders may even be improperly diagnosed as a cerebellar syndrome [12]. Therefore, if imbalance is in excess of that expected for the severity of the neurological disorder, one should consider a coexisting BVH [23]. …”

“…Nowadays, this symptom complex is known to have many causes, and BVH probably represents a functionally heterogeneous disorder with different combined or isolated deficits of the semicircular canals and/or otolith organs [18]. Most of the etiologies described are presented in table 1[12,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44]. However, its etiology still remains unclear in approximately 50% of all cases [7,19].…”

Dorsal root ganglionopathy is responsible for the sensory impairment in CANVAS

“…We refer the reader to our earlier work for details of the VVOR. 1 While the initial description of a syndrome of cerebellar ataxia and bilateral vestibulopathy noted the presence of a peripheral neuropathy in 3 of the 4 index cases, we later showed that in 18 patients a peripheral nerve disease was an integral component of the syndrome we renamed cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS). 2 At this time, we noted that a neuronopathy (ganglionopathy) could not be definitively excluded.…”

Clinical diagnosis of bilateral vestibular loss: three simple bedside tests

“…BVL may also be associated with multiple system atrophy, neurofibromatosis type 2, hereditary ataxias such as Friedreich's ataxia [Fahey et al 2008], spinocerebellar ataxia [Gordon et al 2003] and episodic ataxia type 2. A combination of vestibular loss, peripheral neuropathy and bilateral vestibular areflexia is known as CANVAS syndrome [Szmulewicz et al 2011].…”