Brachycephaly
Brachycephaly (also: brachycephaly, from Greek βραχύς brachýs 'short' and κεφαλή kephalḗ 'head') means short-headedness or round-headedness. It is a congenital, hereditary deformation of the skull that leads to various health problems. Dogs and sometimes cats are particularly affected among domestic animals .
definition
The definition of a skull as brachycephalic is based on several criteria. On the one hand, the outward appearance of an entire race is used, the skull shape of relatively original representatives of the species Canis lupus familiaris is used as a benchmark and, in relation to this, short and wide skulls are called brachycephalic. On the other hand, skull measurements are used to classify an individual as brachycephalic. This can lead to the fact that in some races not considered to be brachycephalic, individuals with a brachycephalic skull can very well be found. These include, for example, the Norwich Terriers . This general dilemma cannot be resolved, especially since the permanent and breeding- induced change in the shape of the skull is rapid.
The known skull measurements are:
- Ratio of skull width to skull length of 0.81 or higher
- Ratio of brain skull to facial skull greater than 1.6
- Craniofacial angle (CFA) between 9 ° and 14 °
- Ratio of facial skull to brain skull less than 1.25 (S index)
The first two indices are collected after the dog dies. For the CFA and the S-Index, however, the examiner uses X-rays , which has the great advantage that the measurements can also be carried out on living dogs. The craniofacial angle is the angle bounded by the tip of the snout, the base of the skull, and the center of the eye socket . However, massive overlaps in the three skull shapes ( brachycephal = short head; mesocephal = medium- long head, doolichocephal = long head) were found, so that the S-index is regarded as a reference measure, at least in Switzerland, because of its clinical application.
Health consequences
Brachycephalic Syndrome
Brachycephaly can cause problems in the upper respiratory tract , collectively referred to as brachycephalic syndrome or brachycephalic syndrome , sometimes called upper airway syndrome (OLS). It is characterized by severe impairment of breathing and impaired thermoregulation . The latter means that these animals are particularly at risk of suffering from heat stroke . In dogs with a natural snout length, there is some evaporation cold on the moist mucous membranes during each inhalation through the nose . This cooling effect during nasal breathing is part of the thermoregulation, which prevents overheating of the inside of the skull. The panting of brachycephalic dogs, which occurs even at rest, is a reaction to overheating, from which they suffer because they do not have a sufficiently long airway and an insufficient evaporation surface in the nose. The cooling nasal breathing can also be restricted by obstructing the airway.
Pathogenesis
The main trigger for the narrowing of the upper airways is an inhibition of the growth in length of the facial skull. However, this inhibition is not associated with a proportional reduction in the number of cells formed in the tissues of the upper respiratory tract, rather the original genetic information usually continues to act in the formation of the tissue.
Due to the voluminous extent of the cartilage of the nostril (in particular the cartilago nasi lateralis dorsalis ) and a reduced mobility of the nostril, the nostrils narrow. The nasal cavity of the growing dog normally elongates and the turbinates , which are still underdeveloped at birth, grow towards each other, but stop growing before the mucosal layers covering them touch each other. This growth inhibition does not occur in brachycephalic dogs - there is a relative conchal hypertrophy (" turbinate overgrowth "). In addition, the turbinates grow as aberrant turbinates beyond what is possible for the size of the nasal cavity. A distinction is made between rostral aberrant turbinates (located in front of the plica alaris ), which narrow the front sections of the middle and lower nasal passages, and caudal aberrant turbinates , which narrow the transition to the nasopharynx ( meatus nasopharyngeus ). In addition, the lamellae of the turbinates in brachycephalic dogs are significantly thicker than in other dogs. The result is that hardly any air can flow through the nose, which is a serious problem for an obligatory nasal breath.
The soft palate of brachycephalic dogs is elongated and thickened. This leads to a constriction of the nasopharynx and, in combination with the relatively large tongue ( relative macroglossia ), also of the oropharynx.
Pathological changes also occur in the area of the larynx , especially in pugs . Here the larynx skeleton is unstable, especially the adjusting cartilage and the epiglottis , so that there is a risk of larynx collapse. In addition, the mucous membrane in the area of the corniculate process is usually excessively developed and swollen, so that it is pulled through the glottis when inhaled and partially displaced.
Breed-specific malformations occur in the area of the windpipe and large bronchi . The cartilage clasps of the windpipe are soft in the pug ( tracheomalacia ), so that they tend to collapse . In contrast, the cartilage braces of the French bulldog are small, but mostly sufficiently stiff ( hypoplastic trachea ). These changes continue to the large bronchi.
Clinical picture
A typical symptom of brachycephalic syndrome is noisy breathing, usually stressed on inspiration , combined with signs of shortness of breath . During the clinical examination, narrow nostrils and nasal cavities , an elongated and thickened soft palate , a shortened pharynx and changes in the larynx can be identified as characteristic findings . In addition, the tonsils can be drawn into the interior of the airways if the negative pressure when inhaling becomes too high. This can lead to breathing problems, attacks of suffocation, fainting, or at least rattling breathing noises and snoring noises. Due to the reduced ability to pant , brachycephalic dogs react more sensitively to heat than their non-deformed conspecifics.
Possible complications of a brachycephalic syndrome are edema of the epiglottis , collapse of the larynx, inversion of the lateral larynx pouches, tracheal collapse , inflammation and / or prolapse of the tonsils, bronchitis and heart failure due to insufficient oxygen saturation of the blood.
An increased susceptibility to heat can also often be observed. Since the turbinates and the lateral nasal glands play an important role in heat dissipation, brachycephalic dogs are often very sensitive to warm ambient temperatures.
therapy
The treatment of brachycephalic syndrome can be conservative or surgical , although weight reduction and conservative treatment with corticosteroids only offer a chance of success in mild cases.
Surgical treatment consists of resection of the tissue that constricts the airways (nostril widening, vestibuloplasty, laser-assisted turbinectomy , soft palate resection , tonsillectomy, etc.) in order to enable more free breathing.
Other complications
The proportional enlargement of the head in connection with the round head shape mechanically leads to an increased risk of difficult births . Even with a caesarean section , the survival rate of brachycephalic puppies is reduced compared to anatomically normal dogs. Brachycephalic races are also more often affected by brain tumors and water head . This predisposition is particularly pronounced in breeds in which chondrodysplasia is also present in addition to brachycephaly . The strong deviation from the normal head shape also leads to an anatomical reorganization of the brain . Brachycephalic dwarf breeds are also often affected by fontanelles that persist into adulthood , which represents an additional risk of injury due to the inadequate protection of the brain in the cranial cavity .
Brachycephaly often leads to a pronounced undershot bite due to the shortening of the upper jaw ( brachygnathia superior ) , which is also expressly required in the standard for some brachycephalic breeds . In some cases, this can lead to poor dentition .
In the extremely round-headed breeds (e.g. pugs), protruding, sometimes enlarged eyes can also be observed, which leads to frequent injuries to the cornea . There is also a risk of an eyeball prolapse. This symptom complex is occasionally referred to as ocular brachycephalic syndrome.
Brachycephaly not only shortens the facial skull, but also the brain skull and the base of the skull take on a different shape. As a result, in some dogs of the Cavalier King Charles Spaniel breed, the genetic make-up for the shape of the cerebellum or for the space available to the cerebellum inside the skull has changed in such a way that the physiologically necessary outflow of cerebrospinal fluid through the occipital cavity is impeded and a secondary syringomyelia develops.
Genetics and Breeding Hygiene
Brachycephaly is a complex of different anatomical features that are polygenically inherited. Brachycephaly is the result of selective breeding when the face shape of the animals approximates the child pattern . For reasons of animal welfare, extremely brachycephalic animals are to be excluded from breeding. In particular, the extreme round head in combination with a pronounced shortening of the facial bones is to be combated by breeding, which is possible by setting limit values and an index selection and breeding value estimation based on them .
Breeding attempts to combat brachycephaly and brachycephalic syndrome are for example the Continental Bulldog and the Olde English Bulldogge .
Affected races
The following breeds are affected by the occurrence of brachycephaly and the consequences due to the development of breeding in recent decades:
- dogs
A disease similar to the brachycephalic syndrome in a not clearly brachycephalic dog breed has been described in the Norwich Terrier, whose skull has only a limited brachycephalic anatomy.
Legal situation
Germany
According to a report by the Federal Ministry of Food and Agriculture, strong manifestations of brachycephaly are considered prohibited torture breeding . The expert opinion recommends that the breed societies investigate affected animals, breed restrictions and change breeding standards.
In § 11b of the Animal Welfare Act , which regulates the prohibition of torture breeding, is stipulated:
"It is forbidden to breed vertebrates [...] if it is to be expected that in the offspring, [...] hereditary parts of the body or organs for the appropriate use are missing or unsuitable or altered, resulting in pain, suffering or damage. "
Austria
In the Federal Law on the Protection of Animals, Section 5, shortness of breath is named as one of the health effects of torture breeding, so that subsequently the breeding, but also the import, acquisition, transfer or exhibition of such animals is prohibited. According to § 38, violations of § 5 are punishable with a fine of up to 7,500 euros, in the event of repetition up to 15,000 euros. However, according to § 44. (17), there is a transition period in which there is no violation through written documented breeding measures that ensure compliance with the provision until January 1, 2018.
Further use of the term
The term brachycephaly can be found in the literature ( anthropology and ethnology ) of the 19th century. There an attempt was made to classify the human races (quote from) by measuring the skull .
In human medicine, the term brachycephaly is used to describe (congenital) growth disorders such as achondroplasia .
literature
- Lowell J. Ackerman: The Genetic Connection. A Guide to Health Problems in Purebred Dogs . American Animal Hospital Association Press, Lakewood CO 1999, ISBN 0-941451-93-3 , p. 177.
- Thomas Bartels, Wilhelm Wegner: undesirable developments in domestic animal breeding. Breeding extremes and breeding defects in livestock and hobby animals. Ferdinand Enke, Stuttgart 1998, ISBN 3-432-28131-5 .
- Alexander Herzog : Pareys Lexicon of Syndromes .. Hereditary and breeding diseases of domestic and farm animals. Parey, Berlin 2001, ISBN 3-8263-3237-7 , p. 68 ff.
Individual evidence
- ^ Daniel A. Koch, Susanne Arnold, Madeleine Hubler, Pierre M. Montavon: Brachycephalic Syndrome in Dogs . In: The Compendium on Continuing Education for the Practicing Veterinarian . tape 25 , no. 1 , 2003, ISSN 0193-1903 , p. 48–55 ( online (PDF; 115 KB) [accessed on August 21, 2012]). online (PDF; 115 KB) ( Memento of the original from March 27, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ S. Regodón, JM Vivo, A. Franco, MT Guillén, A. Robina: Craniofacial angle in dolicho-, meso- and brachycephalic dogs: radiological determination and application. In: Annals of Anatomy - Anatomischer Anzeiger . Vol. 175, No. 4, 1993, pp. 361-363, PMID 8363043 , doi: 10.1016 / S0940-9602 (11) 80043-9 .
- ^ D. Koch, T. Wiestner, A. Balli, P. Montavon, E. Michel, G. Scharf, S. Arnold: Proposal for a new radiological index to determine skull conformation in the dog. In: Swiss Archives for Veterinary Medicine. Volume 154, Number 5, May 2012, pp. 217-220, ISSN 0036-7281 . doi: 10.1024 / 0036-7281 / a000331 . PMID 22547337 .
- ↑ Jenny McIntosh: Heat Stroke - A Seasonal Challenge . In: small animal concrete volume 20, 2017, issue 2, pp. 23–31.
- ↑ Federal Veterinary Association: A brochure on the education about the brachycephalic syndrome
- ↑ Frauke Rödler: Investigation of the influence of brachycephalic malformations on different areas of the dog's life on the basis of a preoperative owner survey of the Veterinary Medicine Faculty of the University of Leipzig 2014, pages 10–11
- ↑ Matzke: FQA Brachycephaly ( Memento of the original from September 20, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Fürstenwalde Small Animal Clinic
- ↑ a b c d e f Gerhard Oechtering: The Brachycephalic Syndrome - New information on an old hereditary disease. In: Veterinary Focus. Vol. 20, No. 2, 2010, ISSN 0965-4593 , pp. 2–9, online (PDF; 594 KB) ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. .
- ↑ Hofheim Animal Clinic: Information on Brachychepal Syndrome in Dogs and Cats
- ^ PF Moon, HN Erb, JW Ludders, RD Gleed, PJ Pascoe: Perioperative risk factors for puppies delivered by cesarean section in the United States and Canada. In: Journal of the American Animal Hospital Association. Vol. 36, No. 4, 2000, ISSN 0587-2871 , pp. 359-368, PMID 10914537 .
- ^ Taryn Roberts, Paul McGreevy, Michael Valenzuela: Human induced rotation and reorganization of the brain of domestic dogs. In: PloS one. Volume 5, number 7, 2010, p. E11946, doi: 10.1371 / journal.pone.0011946 , PMID 20668685 , PMC 2909913 (free full text).
- ↑ Diseases of the eyelids ( Memento of the original from October 29, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. on the website of the University of Veterinary Medicine, Vienna .
- ↑ Monika Lauritsen - Cavalier King Charles Spaniel Club Germany: http://www.ccd-cavaliere.de/zucht-SM-CM.html
- ↑ Daniel Koch: New Findings on Brachycephalic Syndrome in Dogs ( Memento from December 13, 2013 in the Internet Archive ). (PDF; 83 kB).
- ↑ Expert opinion on the interpretation of § 11b of the Animal Welfare Act (prohibition of torture breeding). From October 2005 , pp. 27 f, 36, 51 and 54
- ↑ Federal Act on the Protection of Animals (Animal Protection Act - TSchG) .
- ^ Robert Hartmann : Investigations on the peoples of North-East Africa. III. In: Journal of Ethnology . Vol. 2, 1870, pp. 86-111, p. 109, online here .
- ^ Francis A. Burgener, Steven P. Meyers, Raymond K. Tan, Wolfgang Zaunbauer: Differential diagnosis in the MRI. Cardboard special edition. Georg Thieme, Stuttgart et al. 2005, ISBN 3-13-141211-9 , p. 178, online here
- ^ Rudolf Virchow : About cretinism, especially in Franconia, and about pathological skull shapes. (Continuation). In: Negotiations of the Physical-Medicinal Society in Würzburg. Vol. 2, No. 16, 1851, ISSN 0931-6493 , pp. 241-256, here p. 242, here online .
Web links
- Federal Veterinary Association: A brochure on the education about the brachycephalic syndrome
- Information and literature from the Leipzig University Clinic for Small Animals
- Ongoing research project at the University of Zurich (English)
- Marie Nitzschner: Why short-headed races suffer. Article from October 8, 2017 with further links, including a lecture by Kyle Snowdon, Michigan State University: "Brachycephalic airway syndrome".
