- Type Disease
Dermoid sinus is a tubular indentation of the skin in the middle of the back, that may go as deep as the spinal canal. The tracts may be single or multiple.\nThis condition occurs because of an abnormality early in embryonic development, in which there is incomplete separation of the tissues that will become the skin and the nervous system.\n\n
- How Transferred
Various modes of inheritance have been suggested including dominant with incomplete penetrance, or recessive. It is possible that there is an inherent deficiency in the Rhodesian Ridgeback breed in the absorption or utilization of folic acid (a B vitamin), that leads to this defect.
- What to Look for
Dermoid sinus is present from birth, although the condition is usually not noticed until later. The tracts contain debris from the skin - sebum (waxy lubricating substance), dead skin cells, and hair - and commonly become infected and painful. If the tract extends to the spinal canal, infection may cause meningitis or myelitis, resulting in various neurologic signs such as local or general spinal pain, stiffness, or weakness (depending on the location of the sinus).
You or your veterinarian may notice firm painful swellings in the middle of your dog's back, from which there may be some exudate. A cord of fibrous tissue (the tract) can usually be felt under the skin. Your veterinarian will take x-rays using a contrast dye to determine the extent of the tract.
In an affected dog, the only successful treatment is surgical removal of the the whole tract, which may be a simple procedure or it may be fairly complicated if the tract extends into the vertebrae and spinal canal. Incomplete removal results in recurrence.\nThere is evidence that suggests folic acid supplementation of breeding bitches (both before and during pregnancy) can reduce the occurrence of this condition (see below).\nFor the veterinarian: Meningitis or myelitis are treated as appropriate. Laminectomy may be necessary to remove portions of the tract from within the spinal canal.\n
- Veterinarian Information
Clinical signs of meningitis or myelitis may be seen. In these cases, a CSF tap is generally abnormal, consistent with bacterial infection. Fistulography using a dye non-irritating to nervous tissue (eg. metrizamide) or myelography will show whether the sinus communicates with the subarachnoid space.
- Breeding Considerations
Affected dogs and their close relatives should not be bred. Breeders may want to consider folic acid dietary supplementation of breeding bitches (see reference below).
- Known Breeds Affected
Rhodesian ridgeback\nBoxer\nShih tzu\nKerry blue terrier\nYorkshire terrier