Vestibular Hypofunction in ARSACS Syndrome: A Possible Pitfall in the Differential Diagnosis of Recessive Cerebellar and Afferent Ataxias.

Objectives:Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is an early-onset ataxia characterized by cerebellar dysfunction, spasticity, and sensory-motor polyneuropathy due to variations in the SACS gene (13q11). To date, no studies have instrumentally assessed vestibular function in this condition. Methods:We report a 36-year-old woman with diagnosis of ARSACS syndrome due to homozygous mutation (c.12232 C>T, p.Arg4078Ter) in the SACS gene. Neurologic examination showed spastic-ataxic gait, dysarthric speech, 4-limb ataxia, and spastic hypertonia with lower limb hyperreflexia. Results:A vestibular instrumental evaluation including bedside oculomotor testing found gaze-evoked and rebound nystagmus on horizontal and vertical gaze, saccadic movements within normality ranges, saccadic pursuit, and slightly impaired visually enhanced vestibulo-ocular reflex (VVOR). A near-normal VOR suppression (VORS) was recorded. Neither head shakings, skull vibrations, nor supine positionings could evoke nystagmus. Finally, the video-head impulse test detected a symmetrical VOR impairment for all the semicircular canals (SCs), mostly involving the horizontal SCs, with corrective saccades in all planes. Discussion:Vestibular hypofunction may be found in ARSACS syndrome and may represent a possible pitfall in the differential diagnosis of recessive cerebellar and afferent ataxias. In this setting, ARSACS syndrome should be considered in the differential diagnosis of CANVAS.