Manx cats have varying degrees of sacral and/or caudal vertebral deformities. Some tailless cats have a normal sacrum, spinal cord and cauda equina. Others show varying dysgenesis or agenesis of the sacral and/or caudal vertebrae that may be associated with spina bifida, malformations of the terminal spinal cord and cauda equina. Spinal cord malformations include the absence or partial development of sacral and caudal spinal cord segments or cauda equina, myelodysplasia, meningocele, meningomyelocoele, duplication of sacral segments, myeloschisis (cleft within the spinal cord), syringomyelia in the lumbar and sacral spinal cord segments, shortening of the spinal cord and subcutaneous cyst formation. These spinal cord and cauda equina malformations are associated with variable neurological deficits.
Sacrocaudal dysgenesis is inherited as an autosomal dominant trait and maybe lethal in some homozygote cats. The condition and its associated malformations have been recognised in most breeds of cats, many nof of true Manx breeding.
Clinical signs are variable depending on the degree of spinal cord and cauda equina malformation, and include paraparesis, paraplegia, megacolon, atonic bladder, absent anal and urinary bladder sphinctei tone, absent anal reflex, urinary and faecal incontinence, and perineal analgesia (Figure 7.9). Affected cats often walk with a plantigrade posture of the hindlimbs and a 'bunny-hopping' gait. Vertebral abnormalities may
be palpable in the lumbosacral region, and in some cats a meningocoele may be detected in the skin and CSF may drain from the site.
Clinical signs are usually evident soon after birth and may progress or remain static. Worsening of neurological deficits may be due to progressive syringomyelia in the lumbar and sacral spinal cord.
Diagnosis is made on the basis of clinical and radiological findings indicating dysgenesis or agenesis of the sacral and caudal vertebrae. Myelography may demonstrate meningocoele or attachment of spinal cord to subcutaneous tissues in the lumbosacral region. The degree of spinal deformity does not always correspond to the severity of the neurological signs. Clinical signs are the most important factors to consider in determining prognosis.
The prognosis for severely affected cats is frequently hopeless and treatment is not available. Cats with urinary and faecal incontinence may be managed with manual bladder expression and faecal softening agents, but recurrent urinary tract infection, megacolon and chronic constipation are common problems. Meningocoele in cats with minimal neurological deficits may be surgically correctable. Many tailless cats do not have neurological signs, and sacral and caudal deformities often are incidental radiological findings.
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