Dermoid Sinus is a hereditary defect found in the Rhodesian Ridgeback breed.
The first description of the condition was recorded in Great Britain by Hare in 1932 who suggested that it resembled Trichostasis spinulosa in humans. Steyn and Others (1939) described the condition independently in South Africa and originated the term Dermoid Sinus.
It is generally accepted that the defect arises when there is incomplete separation between the skin and spinal cord when the skin and the central nervous system are developing. Thus the Dermoid Sinus occurs in the dorsal mid line and it is very rare for a sinus to occur actually within the area of the ridge although it may appear from the anterior part of the neck to the tail. A sinus at the tail head is quite common and it may be difficult to raise the skin and palpate the "thread". There may be several sinuses in any one puppy.
The sinus takes the form of a tube opening at the skin surface and running a varying depth toward the spine. The lining grows hair and has sebacious glands - Dark hair may project through the external opening.
There are four main types of sinus recorded:-
The first only penetrates the subcutaneous tissue; the second does not penetrate to the supraspinous ligament but is attached to it by fibrous strand; the third penetrates the supraspinous ligament, and the fourth type passes through the spinal column and is attached to the dura mater. The effect on the animal varies directly in proportion to the depth of penetration i.e. ranging from boil like eruptions at skin level to severe spinal pain and paralysis. A Dermoid Sinus is a progressive condition and is not self limiting.
All puppies should be checked for sinus as as possible after birth. Puppies should checked and rechecked again and again preferably by at least two people who have seen the condition previously.
checking for Dermoid Sinus is carried out by gently raising the skin immediately behind the head and passing the fold between the forefinger and thumb slowly down the length of the back. The sinus can be felt as a fine thread. Care must be taken to differentiate between a sinus and fine muscle strands which may be felt especially in the neck and shoulder region. If there is doubt, raise the skin in front of and behind the suspect area and the sinus will appear as a depressed area. If the site is clipped or shaved, a small, dark hole is visible and using a lens it may be possible to see hairs protruding therefrom.
Unfortunately a sinus may be missed and found at a later date. It is possible to operate on these cases but surgery may be protracted, complicated and perhaps unsuccessful as well as costly.
If surgery is to be undertaken it should not be comtemplated without also spaying or astrating the patient. Under NO circustances should an animal which has had a sinus be bred from.
It is advisable that veterinary injection in Ridgebacks be carried out away fron the midline thereby prventing any reaction to an injecton being mistaken for a sinus and, much more importantly, an undetedted sinus cannot then be attributed to faulty injection technique.
In cnclusion, anyone wishing more detailed discourse on the subject is recommended to read the article "Dermoid Sinus in the Rhodesian Ridgeback"by G.E. Mann and J Stratton published in the "Journal of Small Animal Practice"Vol 7 1966 pp 631-642 Pergamon Press Ltd. This is the most authoriatative writing on the subject.
Article from : "Guide to the Rhodesian Ridgeback" published by The Rhodesian Ridgeback Club of Great Britain.
National Rhodesian Ridgeback Council of Australia Inc