Pathological Features of Polyneuropathy in Three Dogs

Abstract

ABSTRACT. Canine polyneuropathy is a neurological disorder characterized by a dysfunction of multiple peripheral nerves. The etiology of the disease is diverse; it may occur in cases of infectious, immune-mediated, or hereditary conditions or in association with endocrinopathy, neoplasm, or chemical intoxication. It is often difficult to determine the etiology through clinical symptoms. The aim of this study is to investigate pathological differences among three canine polyneuropathy cases with each presumably having a different etiology. Cases included a 13-month-old female border collie (Dog No.1), a 21-month-old male chihuahua (Dog No.2) and an 11-year-old male beagle (Dog No.3 Polyneuropathy in dogs is a neurological disorder characterized by a dysfunction of multiple peripheral nerves. Initial symptoms of the disease are a lack of coordination and instability, and often progress to decreased reflexes and muscle tone, paralysis, and sensory deficits [45]. Electromyographic evidence of denervation and decreased nerve conduction velocity has been observed in affected nerves [45]. Somatic nerve dysfunctions are most predominant, and autonomic nerves may also be affected. As autonomic dysfunction may lead to laryngeal or pharyngeal paralysis, aspiration pneumonia is frequently diagnosed as a cause of death in canine polyneuropathy cases [6,16,26,32,46].Several etiologies of polyneuropathy in dogs have been previously proposed. In some cases, the disease occurs in association with Neospora caninum infection [10] or some immune-mediated diseases, such as systemic lupus erythematosus [11]. Primary autoimmune diseases against peripheral nerve myelin may also lead to the disease [1,51]. Some seem to occur in specific breeds, indicating that hereditary, familial or breed-associated factors are related to the etiology of the disease [17]. It may also be associated with endocrinopathy including diabetes mellitus [27,34,47] and hypothyroidism [25,49], intoxication of n-hexane [37] or acrylamide [20], administration of cisplatin [36] or vincristine [21], or paraneoplastic syndromes in cases of insulinoma [3,5], multicentric lymphoma [5], or disseminated carcinoma [5]. It is often difficult to distinguish the etiology of this disease through clinical symptoms.The distribution of lesions (i.e. motor or sensory, distal or proximal, anterior or posterior and symmetric or asymmetric) is useful for etiology-based classification of polyneuropathy [7,8,10]. In the human-inherited polyneuropathy, CharcotMarie-Tooth (CMT) disease, classification is established according to lesion distribution, age onset, progression speed and pathological features [18], and a number of genetic mutations have been identified in respective subtypes [7,43]. In contrast, little information on genetic factors has been accumulated in canine-inherited polyneuropathy [8]. So far, canine-inherited polyneuropathy has been reported in 22 breeds, but underlying genetic defects are not yet confirmed in most breeds [8,17].The aim of this study is to investigate ...

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“…Similarly, the association between hypothyroidism and both KCS in dogs 29 and polyneuropathy in dogs and humans has been reported 37,38 . In the present study, a single case had controlled hypothyroidism with Horner's Syndrome.…”

“…In the present study, a single case had controlled hypothyroidism with Horner's Syndrome. While there is little evidence to prove a causal relationship between hypothyroidism and neuropathy in dogs, 39 histopathological findings on necropsy of motor and sensory nerve roots in a dog with hypothyroidism and polyneuropathy were similar to the pathological features seen in humans (demylination and interstitial edema possibly associated with axonal atrophy) with the same disease 38 …”

“…While there is little evidence to prove a causal relationship between hypothyroidism and neuropathy in dogs, 39 histopathological findings on necropsy of motor and sensory nerve roots in a dog with hypothyroidism and polyneuropathy were similar to the pathological features seen in humans (demylination and interstitial edema possibly associated with axonal atrophy) with the same disease. 38 The majority of dogs in this study received treatment with either oral pilocarpine, topical cyclosporin, or a combination of the two. Pilocarpine is both a muscarinic agonist and a direct-acting parasympathomimetic with non-specific stimulation of the parasympathetic nervous system.…”

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