Syringomyelia in a Newborn Male Simmental Calf

Malformations of the spine and spinal cord are common in domestic mammals. Among these, syringomyelia is defined as a cystic, fluid filled tubular cavity (syrinx) within the spinal cord extending over several segments. Syringomyelia occurs as a primary congenital malformation and is most commonly combined with neural tube defects. However, it can also be acquired after alterations in cerebrospinal fluid pressure (CSFP), following rupture of a hydromyelia, trauma, neoplasia, or inflammation. In chronic cases, the cavities can be lined with reactive astrogliosis. Syringomyelia has been most intensively studied in Cavalier King Charles Spaniels but occurs in other mammals. It was previously considered a rare condition in small animal medicine, but because of higher prevalences in certain dog breeds and the increased availability of magnetic resonance imaging (MRI), it has become a relatively common neurological diagnosis. Syringomyelia develops outside the central spinal canal and the cyst is lined by glia cells, whereas hydromyelia affects the central canal and is lined by ependymal cells. The distinction between syringomyelia and hydromyelia is arbitrary; hydromyelia might extend into the spinal cord and form syringohydromyelia partially lined by ependyma and cavities might communicate with the central canal. At present, the term syringomyelia is generally accepted for all spinal cord cavitations containing cerebrospinal or similar fluids. A maldeveloped cerebellum with elongated cerebellar tonsils through the foramen magnum (Arnold-Chiari malformation) is seen in human infants and calves of many breeds. Congenital malformations affecting the cerebellum, such as Chiari-like malformation with displacement of the cerebellum through the foramen magnum, or Dandy-Walker syndrome with cerebellar hypoplasia, cysts in the fourth ventricle and hydrocephalus often occur in combination with syringohydromyelia. Other congenital disorders affecting the spinal cord are described in the literature, from spinal dysraphism, spina bifida and spinal dysraphism, segmental aplasia of the cord and segmental hypoplasia.