Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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December 30, 2021
Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS)
- Background:
- ARSACS is a neurodegenerative disorder that is characterized by cerebellar ataxia, pyramidal tract signs, and peripheral neuropathy.
- Patients present with gait disturbance and walking difficulties at a young age (12–18 months), which progress throughout life.
- Patients are expected to be in a wheelchair by the fifth decade of life.
- Clinical Presentation:
- Progressive spasticity, gait disturbance, and walking difficulties
- Retinal hypermyelination (without vision loss) – predominantly in Quebec
- Mitral valve prolapse
- Pes cavus
- Bladder dysfunction
- Key Diagnostic Features:
- Atrophy of upper cerebellar vermis and cervical spinal cord
- T2-hypointense pontine striations
- T2 hyperintensity around the thalami
- Nerve conduction studies
- Loss of sensory nerve conduction
- Reduced motor conduction velocities
- Autosomal recessive mutations in SACS gene
- The SACS gene encodes the sacsin protein, which is expressed in the brain, skin, skeletal muscles, and minimally in the pancreas.
- Differential Diagnoses:
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Friedreich ataxia: The most common hereditary progressive ataxia (autosomal recessive) due to GAA trinucleotide repeat that disrupts the production of frataxin; typically present with decreased AP diameter of the medulla oblongata and cervical spinal cord combined with symmetric T2 hyperintensity in the lateral or dorsal columns of the spinal cord; relative preservation of the cerebellar volume or mild upper vermian atrophy
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Ataxia with vitamin E deficiency (AVED): Autosomal recessive vitamin E deficiency that affects the central nervous system; MRI is typically normal or may show mild cerebellar and vermian atrophy.
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Troyer syndrome: Also known as spastic paraplegia type 20 (SPG20); part of a group of hereditary spastic paraplegia disorders (autosomal recessive), which cause progressive spasticity of leg muscle and paraplegia; MRI findings are often nonspecific but can include T2 hyperintensity in the periventricular white matter, temporoparietal more than frontal, and the posterior limbs of internal capsules.
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Spinocerebellar ataxia type 3 (SCA3): The most common SCA worldwide; SCA3 is an autosomal dominant hereditary ataxia caused by trinucleotide repeat expansion in the ATXN3 gene coding for the protein ataxin-3; typical MRI findings include atrophy of the vermis, cerebellar hemispheres, and middle cerebellar peduncles, and in the later stages can show linear hyperintensities in the midline of the pons coursing in an anteroposterior direction.
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Treatment:
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Symptomatic – controlling spasticity with physical therapy, pharmacotherapy, and use of ankle foot orthotics
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