See a vet now if a dog with a lump, opening or draining spot along the top of the neck or back has neck or back pain, weakness or wobbly legs, loss of bladder control, or a fever. In some dogs the sinus reaches the spine, and case reports describe back pain, leg weakness and infection of the coverings of the spinal cord (meningitis) [1][2][7][8].
Never squeeze or drain it at home. Pressing, lancing or flushing the opening yourself is not safe. Leave it alone and let your vet examine it.
What it is
A dermoid sinus is a defect a puppy is born with. While the puppy develops in the womb, the tissue that will become the spinal cord (the neural tube) fails to separate fully from the skin [1][2]. What is left behind is a narrow tube or pocket lined with skin, hair follicles and skin glands, running from the midline of the back down into the tissues below [2]. Researchers who studied Rhodesian Ridgebacks in Germany describe it as a tube-shaped dip in the skin on the midline, in front of or behind the ridge, that goes to a variable depth [3].
Vets sort these sinuses into types by how deep they go. In the shallower types the tube ends in or near the ligament that runs over the tops of the spine bones. In deeper types it passes into the spinal canal and attaches to the outer covering of the spinal cord (the dura) [1][2]. Some reports also sort them by where they open: on the midline of the back, on the head, or on the nose [2].
Which dogs are affected
- Rhodesian Ridgebacks and their crosses are the best-known group. In this breed the condition is considered hereditary [1][2].
- It has also been reported in many other breeds, including the Yorkshire Terrier, cocker and springer spaniels, Chow Chow, Golden Retriever, Siberian Husky, French Bulldog, Dachshund, Chinese Crested, Swedish Vallhund and Cane Corso [1], as well as the Shiba Inu and a Labrador Retriever mix [1][2][7][8]. In these breeds it seems to occur sporadically [1].
How it is inherited
In Ridgebacks, the hair ridge comes from a dominant gene change, a duplicated stretch of DNA that includes three growth factor genes, and the same change makes a dog more likely to have a dermoid sinus [4]. A Swedish study of Ridgeback litters found that dogs carrying the ridge are predisposed [5]. A later study of more than 12,000 Ridgeback puppies born in Germany found dermoid sinus in about 2.5% of them, with the rate falling over the years, and concluded that the inheritance is more complex than a single gene [3].
What you may notice
- Where: usually on the midline of the neck or back, sometimes on the head [1][2]. A dog can have more than one [2].
- What it looks like: a small opening, a tuft of hair or a lump on the midline. One Shiba Inu was first seen as a 4-month-old puppy because of a tuft of hair on the upper back [7].
- On the nose: a rarer form opens on the bridge of the nose. In six dogs with this form, the owners had noticed discharge that came and went from a tiny hole on the midline of the nose [6].
- Infection and discomfort: when the same Shiba Inu came back a year later, the area smelled bad, was red and itchy and hurt when touched, and the dog was eating less [7].
- Nerve signs: in deep sinuses that reach the spinal cord covering, infection can spread inward and cause nerve problems [1][2]. Case reports describe a dog with back pain, hind legs too weak to walk on and urine leaking [1], a young dog with worsening hind leg problems and repeated bouts of suspected meningitis [8], and a puppy that had trouble breathing and then lost the use of all four legs [2].
Sinuses that reach the spinal cord are uncommon [2], so most dogs do not have nerve signs. But they can happen, and they need a vet at once.
How it is diagnosed
- Examination: your vet feels along the midline of the head, neck and back and checks the nerves.
- Imaging: in a series of nine dogs, a CT scan helped confirm the diagnosis and plan the operation [9]. Other reports used CT and MRI to see how deep the tract runs and whether it reaches the spine [1][2][7]. When a sinus is thought to reach the spinal cord covering, one report advises testing the fluid around the spinal cord for inflammation [1].
- Tissue check: after removal, the tissue is examined under the microscope to confirm the diagnosis [1][7][8].
Your vet chooses the tests for your dog.
Treatment
Surgery to remove the sinus is the usual treatment, and it is the preferred option when there are nerve signs [1].
The aim of surgery is to take out the whole tract. In the nine-dog series, the surgeons often found the tract going deeper than the scan showed, ending on a spine bone, and they stressed that careful dissection past the deep neck ligament is needed to remove it completely [9]. So your vet or a surgeon plans the operation carefully.
If there is infection or nerve involvement, your vet treats that too. Do not squeeze, lance or flush the opening at home.
Outlook
Outcomes vary between studies:
- Removing the sinus completely is linked with a good outlook, while the outlook for dogs with nerve signs is more guarded [1].
- All six dogs with the nose form did well once the whole tract and cyst were removed, and the authors described the outlook after complete removal as good [6]. Before surgery, antibiotics had not cleared the problem in these dogs [6].
- In a report of three dogs and a cat with a dermoid sinus and a spine defect, all the dogs had surgery and all were judged to have done well [10].
- The Shiba Inu with back pain and weak legs had no more back pain after surgery and could walk and pass urine normally again at a check-up some months later [1].
- The puppy that had lost the use of its legs was walking on its own again within about two weeks, and the nerve signs did not come back [2].
- The nose-form authors also warned that these sinuses can reach inside the skull and lead to brain abscesses or repeated meningitis [6].
These are findings about small groups of dogs in particular studies. They do not prove that a treatment caused an outcome, and they cannot predict how one dog will do. Your vet can explain what this means for your dog.
When to see your vet
See a vet now if your dog has a midline lump, opening or draining spot and:
- back pain [1] or neck pain;
- weakness, wobbly or dragging legs [1][2][8];
- loss of bladder control [1];
- seems unwell or stops eating [7], or has a fever.
Book a visit if you notice:
- a small opening, tuft of hair or lump on the midline of the head, neck or back, especially in a puppy [1][2][7];
- discharge, smell, redness or itch at such a spot [6][7];
- a draining opening on the bridge of the nose [6].
FAQ
Can I squeeze it or clean it out myself?
No. Do not press, lance or flush it. Let your vet look at it.
Will antibiotics fix it?
Antibiotics may treat an infection, but the sinus itself stays until it is removed. In the nose-form dogs, antibiotics alone did not solve the problem [6], and surgery is the usual treatment [1]. See Outlook above for what studies report.
Is my Rhodesian Ridgeback at risk?
Dermoid sinus is considered hereditary in Rhodesian Ridgebacks [1], and a study found that ridged Ridgebacks are predisposed [5]. Ask your vet to check your puppy’s back.
Do cats get it?
It is rare, but it has been reported in cats, including a Burmese cat [2][10]. If your cat has a lump or opening on its back, ask your vet.
The bottom line
A dermoid sinus is a birth defect: a skin-lined tube along the top of the head, neck or back, hereditary in Rhodesian Ridgebacks and seen now and then in other breeds [1][2]. Never squeeze it. Pain, weakness, loss of bladder control or fever with such a spot means a vet visit now. Surgical removal is the usual treatment [1].
This article is for general information and does not replace a visit to your veterinarian. If your dog has a lump or opening on its back, contact your vet.
Sources
- Takahashi K, Kimura S, Chambers JK, et al. Case Report: Surgical Treatment of Type IV Spinal Dermoid Sinus in a Shiba Inu. Front Vet Sci. 2022;9:849025. Open access, CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC8985408/
- Torres R, Giovanella C, Sessums K. Type I and type IV dermoid sinus with associated cervical spina bifida in a Labrador Retriever mixed breed dog. Vet Med Sci. 2024;10(1):e1319. Open access, CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC10789649/
- Distl O. Prevalence and segregation analysis of dermoid sinus in Rhodesian Ridgebacks. Vet J. 2022;280:105803. https://pubmed.ncbi.nlm.nih.gov/35150843/
- Salmon Hillbertz NH, Isaksson M, Karlsson EK, et al. Duplication of FGF3, FGF4, FGF19 and ORAOV1 causes hair ridge and predisposition to dermoid sinus in Ridgeback dogs. Nat Genet. 2007;39(11):1318-1320. https://pubmed.ncbi.nlm.nih.gov/17906623/
- Hillbertz NH, Andersson G. Autosomal dominant mutation causing the dorsal ridge predisposes for dermoid sinus in Rhodesian ridgeback dogs. J Small Anim Pract. 2006;47(4):184-188. https://pubmed.ncbi.nlm.nih.gov/16573760/
- Anderson DM, White RA. Nasal dermoid sinus cysts in the dog. Vet Surg. 2002;31(4):303-308. https://pubmed.ncbi.nlm.nih.gov/12094342/
- Jeong JE, Kim SY, Kim JI. Complete surgical excision of a type V-variant dermoid sinus (V/VI overlap) associated with spina bifida in a Shiba Inu dog: A case report. Vet Surg. 2026 (online ahead of print). https://pubmed.ncbi.nlm.nih.gov/42760277/
- Blondel M, Deprey J, Moissonnier P. Type IV dermoid sinus, intramedullary dermoid cyst and spina bifida in a Cane Corso. J Small Anim Pract. 2021;62(9):810-815. https://pubmed.ncbi.nlm.nih.gov/33025601/
- Appelgrein C, Hosgood G, Reese SL. Computed tomography findings and surgical outcomes of dermoid sinuses: a case series. Aust Vet J. 2016;94(12):461-466. https://pubmed.ncbi.nlm.nih.gov/27800602/
- Kiviranta AM, Lappalainen AK, Hagner K, Jokinen T. Dermoid sinus and spina bifida in three dogs and a cat. J Small Anim Pract. 2011;52(6):319-324. https://pubmed.ncbi.nlm.nih.gov/21627660/