Spinal Muscular Atrophy (Motor Neuron Disease)
Spinal muscular atrophy is an abiotrophic disease of somatic motor neurons in the ventral gray column of the spinal cord and brainstem nuclei.
Age of Onset: 3 phenotypes
Accelerated form: 6-8 weeks of age
Intermediate form: 6-12 months of age (most common)
Chronic: Greater than 2 years of age
Accelerated form: 6-8 weeks of age
Intermediate form: 6-12 months of age (most common)
Chronic: Greater than 2 years of age
Sex Predisposition: Any sex of animal can be affected
Clinical Course:
Accelerated form: clinical signs progress rapidly, by 3-4 months clinical signs progress to tetraplegia and muscle atrophy
Intermediate form: clinical signs progress more slowly, resulting in tetraplegia and inability to walk by 2-3 years of age (most common)
Chronic: clinical signs develop slowly (months to years) and are milder compared to the other forms if the disease (subtle paresis and mild atrophy)
Accelerated form: clinical signs progress rapidly, by 3-4 months clinical signs progress to tetraplegia and muscle atrophy
Intermediate form: clinical signs progress more slowly, resulting in tetraplegia and inability to walk by 2-3 years of age (most common)
Chronic: clinical signs develop slowly (months to years) and are milder compared to the other forms if the disease (subtle paresis and mild atrophy)
Clinical Signs:
Behavioral/Mental Awareness
Exercise intolerance
Posture and Appearance
Limb deformities (arthrogryposis)
Slow growth
Exercise intolerance
Movement
Tetraparesis to tetraplegia
Wide-based stance
Limb tremor when weight-bearing
Proprioception
Proprioceptive deficits
Cranial Nerves
Difficulty with prehension
Dysphagia
Depressed gag reflex
Decreased tongue muscle tone
Facial muscle weakness (wrinkling of the facial skin and wide palpebral fissures)
Spinal Reflexes
Reduced patellar reflex
Special functions (e.g. respiration; urination)
Labored respiration
Muscle Atrophy
Diffuse neurogenic atrophy of paraspinal and proximal limb muscles (severe/intermediate > chronic forms)
Behavioral/Mental Awareness
Exercise intolerance
Posture and Appearance
Limb deformities (arthrogryposis)
Slow growth
Exercise intolerance
Movement
Tetraparesis to tetraplegia
Wide-based stance
Limb tremor when weight-bearing
Proprioception
Proprioceptive deficits
Cranial Nerves
Difficulty with prehension
Dysphagia
Depressed gag reflex
Decreased tongue muscle tone
Facial muscle weakness (wrinkling of the facial skin and wide palpebral fissures)
Spinal Reflexes
Reduced patellar reflex
Special functions (e.g. respiration; urination)
Labored respiration
Muscle Atrophy
Diffuse neurogenic atrophy of paraspinal and proximal limb muscles (severe/intermediate > chronic forms)
Diffuse neuromuscular
Autosomal dominant mutation in CDK5 gene
*Homozygous dominant dogs develop the accelerated form of the disease, while heterozygous can develop the intermediate or chronic forms of the disease
*Homozygous dominant dogs develop the accelerated form of the disease, while heterozygous can develop the intermediate or chronic forms of the disease
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