Myelodysraphism

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Myelodysraphism (neurospinal dysraphism) is a rare autosomal-dominant genetic neurological disease of dogs characterized by spinal cord malformation[1][2][3].

This disease which develops as a result of abnormal migration of mantle cells, has been reported as a breed predisposition in the Weimaraner in which it is transmitted by a codominant lethal gene with reduced penetrance and variable expression[4].

The homozygous condition is lethal. This disorder has also been reported sporadically in other breeds of dogs, including but not limited to Dalmatian, Rottweiler, West Highland White Terrier, German Shepherd, Golden Retriever and Alaskan Malamute[5].

Vertebral anomalies may be associated with myelodysplasia as a result of the close embryonic origin of the spinal cord and vertebral column (i.e. notochord, neural tube, and sclerotomal mesoderm), e.g., malformations of the vertebral bodies and ribs have been reported in a Pekingese dog with spinal dysraphism, along with agenesis of the cauda equina[6].

Similarly, myelodysraphism may be seen with other developmental conditions, such as spinal canal stenosis[7], spina bifida, meningoencephalocele, syringomyelia, hydrocephalus, and arachnoid cysts.

Pathologically, the malformation includes hydromyelia, duplicated, stenotic, or absent central canal, syringomyelia (usually in dorsal columns and often delayed in its formation until dogs are several months old, chromatolysis and loss of nerve cell bodies in gray matter, disrupted dorsal median septum and ventral median fissure, and gray matter ectopias.

Clinical signs usually appear by 4 to 6 weeks of age; however, abnormal spinal reflexes reportedly are observed in newborn dysplastic puppies. Affected animals have a symmetrical bunny hopping pelvic limb gait, wide based stance, and overextended pelvic limbs with depressed proprioception. Less constant signs include scoliosis, abnormal hair streams in the dorsal neck region, and koilosternia (gutter-like depression of the chest).

Clinical signs neither progress nor retrogress. There is often a poor correlation between the severity of the clinical signs and the histopathological lesions[8].

Diagnosis can be difficult as routine hematology, radiography and CSF analysis are usually within normal limits. A definitive diagnosis requires histopathological analysis of sample tissues

There is no known treatment for this condition but most affected animals tend to lead a normal life.

References

  1. Vite, Ch (2004) Developmental disorders. In: Braund's Clinical Neurology in Small Animals: Localization, Diagnosis and Treatment. IVIS, Ithaca, New York, USA
  2. Engel HN, Draper DD. (1982) Comparative prenatal development of the spinal cord in normal and dysraphic dogs: embryonic stage. Am J Vet Res 43:1729-1734
  3. McGrath JT. (1965) Spinal dysraphism in the dog. With comments on syringomyelia. Pathol Vet 2:1-36
  4. Shelton MC. (1977) A possible mode of inheritance for spinal dysraphism in the dog with a more complete description of the clinical syndrome. MS Thesis. Iowa State University
  5. Geib LW, Bistner SI. (1967) Spinal cord dysraphism in a dog. J Am Vet Med Assoc 150:618-620
  6. Ruberte J, Anor S, Carretero A, et al (1995) Malformations of the vertebral bodies and the ribs associated to spinal dysraphism without spina bifida in a Pekingese dog. J Vet Med 42:307-313
  7. Shell LG, Carrig CB, Sponenberg DP, et al (1988) Spinal dysraphism, hemivertebra, and stenosis of the spinal canal in a Rottweiler puppy. J Am Anim Hosp Assoc 24:341-344
  8. Broek AHMvd, Else RW, Abercromby R, et al (1991) Spinal dysraphism in the Weimaraner. J Small Anim Pract 32:258-260