Diabetic polyneuropathy

From Dog

Diabetic polyneuropathy is a hyperglycemia-induced polyneuropathy[1] frequently observed in diabetic dogs with a sustained hyperglycemia > 20mmol/L over a 3 - 4 month period.

This phenomenon is less frequently observed in dogs compared with cats, due presumably to the dogs higher tolerance to chronic hyperglycemia.

In concert with neuropathy, microvascular pathologies lead to varying degrees of [[nephropathy and retinopathy[2].

Hyperglycemia has been show to cause nerve degeneration in many peripheral nerves including sympathetic nerves (motor nerve to muscles) and autonomic nerves. These changes are thought to involve perineurial thickening and swelling[3], manifesting clinically as a neuropathy of:

  • Vagus nerve - cardiac control[4],
  • Vagosympathetic trunk - Horner's syndrome[5]
  • Pudendal nerve and pelvic splanchnic nerve - dysuria
  • Celiac nerve - loss of intestinal motility control[6]

Clinical signs of polyneuropathy associated with spontaneous diabetes mellitus have been reported in only 4 dogs from 4 different studies[7].

Clinical signs in affected dogs is weakness, muscle atrophy, ataxia, hyporeflexia, hypotonia and hypotension[8]. Urinary incontinence due to diabetic uropathy is also reported in the dogs, due to progressive demyelination of pudendal and splanchnic nerves and consequential bladder nerve dysfunction[9].

The diagnosis of diabetic polyneuropathy is based on clinical signs, electromyographic abnormalities, nerve biopsies, and muscle biopsies. Electrodiagnostic abnormalities consistent with a diagnosis of polyneuropathy include spontaneous electrical activity, decreased M-wave amplitude (suggestive of axonal disease), and markedly slow motor and sensory nerve conduction velocities (suggestive of demyelinating disease)[10].

Histopathological findings consistent with canine polyneuropathy are axonal degeneration with segmental demyelination and remyelination[11].

A differential diagnosis would include discospondylitis and other causes of polyneuropathy.

Treatment is primarily aimed at rectifying the hyperglycemia associated with diabetes.

References

  1. Morgan MJ et al (2008) Clinical peripheral neuropathy associated with diabetes mellitus in 3 dogs. Can Vet J 49(6):583-586
  2. Muñana KR (1995) Long-term complications of diabetes mellitus, Part I: Retinopathy, nephropathy, neuropathy. Vet Clin North Am Small Anim Pract 25(3):715-730
  3. Ghani M et al (1999) Perineurial abnormalities in the spontaneously diabetic dog. Acta Neuropathol 97(1):98-102
  4. Kenefick S et al (2007) Evidence of cardiac autonomic neuropathy in dogs with diabetes mellitus. Vet Rec 161(3):83-88
  5. Holland CT (2007) Bilateral Horner's syndrome in a dog with diabetes mellitus. Vet Rec 160(19):662-664
  6. Guidi WL et al (2008) Diabetes mellitus-related morphoquantitative changes in the celiac ganglion neurons of the dog. Vet J 177(1):54-62
  7. Johnson CA et al (1983) Peripheral neuropathy and hypotension in a diabetic dog. J Am Vet Med Assoc 183:1007–1009
  8. Cuddon PA (2002) Acquired peripheral neuropathies. Vet Clin North Am Sm Anim Prac 32:207–249
  9. Daneshgari F et al (2009) Animal models of diabetic uropathy. J Urol 182(6):S8-S13
  10. Steiss JE et al (1981) Electrodiagnostic analysis of peripheral neuropathy in dogs with diabetes mellitus. Am J Vet Res 42:2061–2064
  11. Ghani M et al (1999) Perineural abnormalities in the spontaneously diabetic dog. Acta Neuropathol (Berl) 97:98–102