Canis ISSN: 2398-2942

Peripheral neuropathies

Synonym(s): Neuropathies; motor neuropathy (spinal muscular atrophy; sensory neuropathy

Contributor(s): Laurent Garosi, Kyle Braund

Introduction

  • Uncommon peripheral nerve disease in which the primary changes appear in the nerve cell body.
  • Includes motor neuron disease Motor neurone disease: Brittany Spaniels , mixed motor and sensory neuropathies, motor neuropathies Motor neuropathy , sensory neuropathies Sensory neuropathies and autonomic neuropathies.
  • Cause: often unknown; can be hereditary, toxic, idiopathic, metabolic, paraneoplastic, infectious or inflammatory.
  • Signs: progressive neurological deficits.
  • Treatment: high quality nursing.
  • Prognosis: poor because generally progressive.

Pathogenesis

Etiology

  • Causes:
    • Hereditary.
    • Toxic.
    • Inflammatory.
    • Traumatic.
    • Infectious.
    • Immune-mediated.
    • Idiopathic.
    • Ischemic.
    • Metabolic.
    • Paraneoplastic.

Pathophysiology

  • Premature degeneration and death of neuronal cell populations in the spinal cord and/or interruption of nerve to target organ → decreased or absent function of target organ.
  • Classification based on:
    • Anatomical position.
    • Distal or proximal axonopathy.
    • Motor or sensory.
    • Pathological change.
    • Axonal degeneration.
    • Segmental demyelination.
    • Etiology.
    • Inherited.
    • Acquired.

Wallerian degeneration

  • Usually follows nerve trauma.
  • Distal to the site of trauma axons die and myelin sheaths degenerate.
  • Schwann cells remain intact for some time in the distal stump of a transected nerve, and proliferate to form columns of denervated Schwann cells also known as bands of Bungner.
  • Regenerating sprouts from the intact axons in the proximal stump penetrate the distal stumps with the denervated Schwann cells that serve to guide regenerating nerve fiber back to target site.

Axonal degeneration (wallerian-like degeneration)

  • Degeneration of axon and myelin sheath starts from distal extremity.
  • Mainly affects large myelinated axons distal axonopathy (dying-back process).
  • Regeneration may occur or adjacent axons may reinnervate denervated muscle fibers.
  • Secondary segmental demyelination → affected axons atrophy prior to degeneration.
  • The sprouting of healthy axons, and their reinnervation of denervated muscle fibers, results in expansion of the motor units and loss of the normal mixing of fibers that make up the units.

Demyelination

  • Axon remains intact but myelin sheath lost along whole or part of length (segmental demyelination).
  • Primary site of damage can be either the Schwann cell or its myelin sheath.
  • Recovery is possible if adjacent Schwann cells proliferate and remyelinate axons.

Timecourse

  • Variable, depends on entity involved.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Harkin K R, Cash W C & Shelton G D (2005) Sensory and motor neuropathy in a Border Collie. JAVMA 227 (8), 1263-1265 PubMed.
  • Mariani C L, Shelton S B, Alsup J C (1999) Paraneoplastic polyneuropathy and subsequent recovery following tumor removal in a dog. JAAHA 35 (4), 302-305 PubMed.
  • Mahony O M, Knowles K E, Braund K G et al (1998) Laryngeal paralysis - polyneuropathy complex in young Rottweilers. JVIM 12 (5), 330-337 PubMed.
  • Zaal M D et al (1997) Progressive neuropathy in two Cairn terrier litter mates. Vet Q 19 (1), 34-36 PubMed.
  • Braund K G, Vallat J M, Steiss J E et al (1996) Chronic inflammatory demyelinating polyneuropathy in dogs and cats. J Peripher Nerv Syst 1 (2), 149-155 PubMed.
  • Braund K G (1996) Degenerative causes of neuropathies in dogs and cats. Vet Med 91 (8), 722-739 VetMedResource.
  • Braund K G, Tovivio-Kinnucan M, Vallat J M et al (1994) Distal sensorimotor polyneuropathy in mature Rottweiler dogs. Vet Pathol 31 (3), 316-326 PubMed.
  • Jaggy A, Oliver J E, Ferguson D C et al (1994) Neurological manifestations of hypothyroidism: a retrospective study of 29 dogs. JVIM 8 (5), 328-336 PubMed.
  • Jeffrey N D et al (1993) Sensory neuronopathy of possible toxic etiology in a dog. Prog Vet Neurol (4), 145-148 VetMedResource.
  • Palmer A C et al (1988) Progressive neuropathy in the cairn terrier. Vet Rec 123 (1), 39 VetMedResource.
  • Braund K G, McGuire J A, Amling K A et al (1987) Peripheral neuropathy associated with malignant neoplasms in dogs. Vet Pathol 24 (1), 16-21 PubMed.
  • Steiss J E et al (1987) Sensory neuropathy in a dog. JAVMA 190 (2), 205-208 VetMedResource.
  • Cummings J F et al (1983) Ganglioradiculitis in the dog. Acta Neuropathol 60 (1-2), 29-39 PubMed.
  • Wouda W et al (1983) Sensory neuropathy in dogs - a study of four cases. J Comp Pathol 93 (3), 437-450 VetMedResource.
  • Griffiths I R, Duncan I (1979) Distal denervating disease: a degenerative neuropathy of the distal motor axon in dogs. JSAP 20 (10), 579-592 PubMed.

Other sources of information

  • Garosi L S (2008) Disorders of peripheral nerves. Handbook of Small Animal Practice. 5th edn, Morgan R V. pp 275-292.
  • Shelton G D (2004) Neuromuscular diseases II. Veterinary Clinic of North America Small Animal Practice.
  • Shelton G D (2001) Neuromuscular diseases. Veterinary Clinic of North America Small Animal Practice.


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