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Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS)

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS)



Overview

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a rare inherited neurodegenerative disorder that affects balance, muscle control, and peripheral nerves

ARSACS is a neuromuscular condition characterized by the progressive degeneration of the cerebellum and spinal cord.

Symptoms

ARSACS is defined by three main clinical features:

Cerebellar ataxia: Balance and coordination problems, leading to a clumsy or wide-based gait, frequent falls, and poor coordination in the arms and hands.

Spasticity: Abnormal, progressive muscle stiffness and tensing, which usually affects the legs more severely over time.

Sensorimotor polyneuropathy: Reduced sensation, weakness, and numbness in the arms and legs due to damage to the peripheral nerves

Musculoskeletal changes: Distal muscle wasting (amyotrophy) in the hands and feet, foot deformities such as high arches (pes cavus), and spinal curvature (scoliosis).

Speech and swallowing difficulties: Ataxic dysarthria (slurred or slow speech) and occasional trouble swallowing (dysphagia).

Eye findings: Involuntary eye movements (nystagmus) and a thickened retinal nerve fiber layer visible during eye exams.

Less frequent features: Urinary bladder dysfunction, hearing loss, cognitive impairment or intellectual disability, and seizures.

Causes

Gene and Protein: Mutations in the SACS gene disrupt the production or function of sacsin, a massive protein highly expressed in the nervous system—particularly in motor neurons and cerebellar Purkinje cells.

Inheritance Pattern: It follows an autosomal recessive inheritance pattern, meaning a person must inherit one mutated copy of the SACS gene from both parents to develop the condition.

Cellular Impact: The lack of normal sacsin leads to impaired cellular function and progressive degeneration in the cerebellum, corticospinal tracts, and peripheral nerves

Diagnosis 

Clinical Evaluation: Doctors look for the classic triad: early-onset cerebellar ataxia (balance and coordination problems), spasticity (abnormal muscle tensing, mostly in the legs), and sensorimotor peripheral neuropathy.

Brain MRI: Imaging often reveals superior cerebellar vermian atrophy (shrinking of the upper cerebellum) and characteristic linear hypointensities or a tigroid/striped pattern in the pons.

Nerve Conduction Studies (NCS) and EMG: Tests show axonal or mixed axonal-demyelinating peripheral neuropathy with reduced or absent sensory nerve responses.

Ophthalmologic Examination: An eye exam using optical coherence tomography (OCT) may show prominent retinal nerve fiber layer hyper-reflectivity or striation.

Molecular Genetic Testing: Definitive confirmation requires identifying biallelic (two copies of) pathogenic mutations in the SACS gene on chromosome 13q through sequencing panels or genetic testing.

Treatment

Physical Therapy (PT): Preserves muscle function, prevents joint contractures, and helps coordinate movement.

Spasticity Management: Uses oral medications like baclofen or localized botulinum toxin injections to relax tight muscles carefully without causing weakness.

Occupational Therapy (OT): Provides adaptive tools, leg braces, and strategies for daily tasks.

Speech and Hearing Support: Employs speech-language pathologists for swallowing or speech difficulties and hearing aids for hearing loss.

Urinary Care: Treats bladder urgency using medications like tolterodine or oxybutynin.

Type of Doctor Department : A neurologist

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