What it is
Early in a puppy's development, the skin and the spinal cord form from the same layer of tissue and then separate. A dermoid sinus is a spot where that separation was left unfinished: a thin tube of skin runs inward from the surface of the back or neck. Some end blindly under the skin; others reach the tissue around the spine or join the spinal canal itself.
The tube is lined with skin, so it keeps producing hair, oil and dead cells that have nowhere to go. It can sit quietly for a long time and then fill up, swell and become infected. It is present from birth and can be inherited.
Gently running your fingers along the middle of a puppy's back, from the head to the base of the tail, is a good habit. If you know your dog has a sinus, keep an eye on the spot after baths, brushing and rough play, and make sure collars and harnesses do not rub it.
Signs you may notice
- Small hole with a tuft of hair
- Cord-like strand under the skin
- Swelling or discharge on the back
- Fever or pain
- Weak, unsteady legs
Along the midline of the back or neck you may feel a small opening with a tuft of hair, or a cord-like strand running under the skin. When it is inflamed the spot swells and leaks discharge, and the dog may run a fever, seem painful or grow weak in the legs.
When to see a vet
Book a visit if you feel an opening or a strand along your dog's spine. Swelling, discharge, fever, pain or weakness in the legs means a vet is needed immediately.
This is general information, not veterinary advice. For your own dog's health, tests and treatment, see a vet.