Canine degenerative myelopathy (DM) is a slowly, progressive adult-onset neurodegenerative disease causing paralysis similar to human amyotrophic lateral sclerosis (ALS – Lou Gehrig’s disease). Canine DM was first described by Averill in 1973 as an insidious, progressive, general proprioceptive (GP) ataxia and upper motor neuron (UMN) spastic paresis of the pelvic limbs ultimately leading to paraplegia and necessitating euthanasia.1 Although initially described in German Shepherd dogs (Averill 1973; Braund 1978), DM is now being recognized as a common neurologic problem in many pure breeds and mixed breeds (Zeng et al., 2014).
Hereditary disease and genetic predisposition.
Dogs with DM exhibit a predictable pattern of clinical signs that begins with UMN pelvic limb paresis and GP ataxia, progress to LMN paraparesis, and then spreads to involve the thoracic limbs and brainstem (Coates et al., 2007; Coates and Wininger 2010; Johnston et al., 2000). The clinical course of DM is rather uniform after the presumptive diagnosis but ambulatory (paresis/ataxia) to nonambulatory status occurs within a median time of 10 months (95% CI, 9-12; unpublished data, Kanazono et al., 2012) from onset of signs. Pet owners usually elect euthanasia when their dogs can no longer support weight in their pelvic limbs. The pet owner can care for smaller dogs over a longer time. The median disease duration in the Pembroke Welsh Corgi was 19 months (Coates et al., 2007).
Pharmacotherapies including drugs and nutritional supplements for canine DM have been advocated; however, the efficacies of these therapies have not been established. The long-term prognosis of DM is poor. Mechanisms for inducing silencing of protein coding genes for SOD1 in ALS like small interfering-RNA, micro-RNA, and antisense oligonucleotides are undergoing clinical trial testing in dogs affected with DM.
Although well-controlled studies are still needed to establish efficacy, physical rehabilitation may have positive effects in early DM. Kathmann et al. reported survival data from 22 DM affected dogs that received varying degrees of physiotherapy (Kathmann et al., 2006). Dogs that received intensive physiotherapy had significantly longer survival times (mean = 255 days) compared to dogs that received moderate (mean = 130 days) or no physiotherapy (mean = 55 days). Study limitations included lack of randomization and definitive diagnosis, small group size, and bias from owner perception; still results warrant further investigation into the efficacy of rehabilitation in DM-affected dogs.
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