General description

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a spinocerebellar degenerative disease associated with SACS gene abnormality characterized by prominent spasticity and hypermyelination of the retinal fibers.

On average, onset at around 5 years of age with gait difficulty and unsteadiness, progressive cerebellar ataxia, dysarthria, spastic paralysis, pathological reflexes, distal muscle atrophy and swan-neck-like hand deformities.

Originally reported as a disease of the Charlevoix-Saguenay region of Quebec, Canada, it was reported worldwide when the SACS gene was implicated. The clinical presentation of the disease became more diverse, with some cases not necessarily showing hypermyelination of the retinal fibers or spasticity.

Radiographic features

Tigroid pattern of pons

Linear T2WI hypointensities were observed in the basal part of the pons and middle cerebellar peduncle, exhibiting a tigroid pattern. However, recent findings demonstrated T2WI and FLAIR hyperintensities in the midline and lateral pons, rendering the aforementioned lesions relatively hypointense.

Lateral thalamus T2WI and FLAIR hyperintensity

On T2WI and FLAIR sequences, linear hyperintense lesions are observed bilaterally within the lateral thalamic regions.

Atrophy

Atrophy of the cerebellar vermis begins early on MRI, followed by bilateral parietal atrophy. Short-stretched thinning of the posterior mid-body of the corpus callosum, and atrophy or thinning of cervical spinal cord may also be observed.

References

1. Cocozza, Sirio, et al. "Conventional MRI findings in hereditary degenerative ataxias: a pictorial review." Neuroradiology 63.7 (2021): 983-999.