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Not all open fontanelles are connected with hydrocephalus. In many young dogs the skull bones are not fused at birth, but instead will close slowly over a three- to six-month period. Occasionally these bones fail to close, but the dog is still healthy. In these cases, however, the dog's owners need
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is known as an "open fontanelle", which occurs when the skull bones at the top of the head fail to close. The problem is often found in conjunction with hydrocephalus, which is a condition in which too much fluid is found within and around the brain, placing pressure on the brain and surrounding
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tissues. Often the head will appear dome-shaped, and the open fontanelle is noticeable as a "soft spot" on the top of the dog's head. The fluid-filled spaces within the brain, known as ventricles, also become swollen. The increased pressure damages or prevents the development of brain tissue.
357:. This pulsating action is how the soft spot got its name – fontanelle is borrowed from the old French word fontenele, which is a diminutive of fontaine, meaning "spring". It is assumed that the term spring is used because of the analogy of the dent in a rock or earth where a spring arises.
305:
Two smaller fontanelles are located on each side of the head, more anteriorly the sphenoidal or anterolateral fontanelle (between the sphenoid, parietal, temporal, and frontal bones) and more posteriorly the mastoid or posterolateral fontanelle (between the temporal, occipital, and parietal
314:
of the bones of the skull causes the anterior fontanelle to close over by 9 to 18 months. The sphenoidal and posterior fontanelles close during the first few months of life. The closures eventually form the sutures of the neurocranium. Other than the anterior and posterior fontanelles, the
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Parents may worry that their infant may be more prone to injury at the fontanelles. In fact, although they may colloquially be called "soft-spots", the membrane covering the fontanelles is extremely tough and difficult to penetrate.
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Sometimes there is a third bigger fontanelle other than posterior and anterior ones in a newborn. In one study, the frequency of third fontanelles in an unselected population of newborn infants was 6.3%. It is very common in
289:
is a diamond-shaped membrane-filled space located between the two frontal and two parietal bones of the developing fetal skull. It persists until approximately 18 months after birth. It is at the junction of the
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The fontanelle may pulsate, and although the precise cause of this is not known, it is normal and seems to echo the heartbeat, perhaps via the arterial pulse within the brain vasculature, or in the
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281:). The posterior fontanelles ossify within 6–8 weeks after birth. This is called intramembranous ossification. The mesenchymal connective tissue turns into bone tissue.
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302:, however, it is often late in closing at 8–24 months or may never close. Examination of an infant includes palpating the anterior fontanelle.
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to be very careful, since any injury or bumps to the animal's head could cause significant brain damage, as well as conditions like epilepsy.
110:
385:. Increased cranial pressure in infants may cause the fontanelles to bulge or the head to begin to enlarge abnormally. It can occur due to:
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368:. Once they are closed, most of the brain is inaccessible to ultrasound imaging, because the bony skull presents an acoustic barrier.
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During birth, fontanelles enable the bony plates of the skull to flex, allowing the child's head to pass through the birth canal. The
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and some congenital infections. If present, the physician should rule out serious conditions associated with the third fontanelle.
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breed standard states that the skull of the
Chihuahua should be domed, with or without the molera being present. However, the
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537:
In apes the fontanelles fuse soon after birth. In chimpanzees the anterior fontanelle is fully closed by 3 months of age.
698:"USMLE Step 2: Secrets".editor1=Theodore X. O'Connell.editor2=Adam Brochert.book=USMLE Step 2: Secrets.ed=3rd.page=271
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both during birth and later as the brain expands faster than the surrounding bone can grow. Premature complete
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The fontanelles may be enlarged, may be slow to close, or may never close, most commonly due to causes like:
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Clinical
Neuroanatomy. 25th ed. New York: Lange Medical /McGraw-Hill, Medical Pub. Division, 2003.
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273:. At birth, the skull features a small posterior fontanelle with an open area covered by a tough
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573:(FCI) standard for the Chihuahua lists an open fontanelle as a disqualification.
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The anterior fontanelle is generally the last to close between 12 and 18 months.
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The sphenoidal fontanelle is the next to close around 6 months after birth;
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This article is about the human anatomical feature. For other uses, see
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The mastoid fontanelle closes next from 6 to 18 months after birth; and
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398:– swelling (inflammation) of the brain, most often due to infections
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The posterior fontanelle generally closes 2 to 3 months after birth;
298:. The fetal anterior fontanelle may be palpated until 18 months. In
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The skull at birth, showing the anterior and posterior fontanelles
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A very tense or bulging anterior fontanelle indicates raised
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In humans, the sequence of fontanelle closure is as follows:
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701:
895:"Open Skull Bones May, May Not Be Sign of Deadly Disorder"
198:. Fontanelles allow for stretching and deformation of the
60:
48:
678:
Center for
Academic Research and Training in Anthropogeny
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A sunken (also called "depressed") fontanelle indicates
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is triangle-shaped. It lies at the junction between the
364:
Fontanelles allow the infant brain to be imaged using
229:An infant's skull consists of five main bones: two
65:
The skull at birth, showing the lateral fontanelles
917:"American Kennel Club – Chihuahua breed standard"
545:One of the more serious problems that can affect
1164:
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638:
410:– infection of the membranes covering the brain
854:
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186:) between the cranial bones that make up the
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27:Anatomical feature of the infant human skull
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749:
439:Anterior fontanelle of a 1-month-old infant
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955:
59:
47:
674:"Age of Closure of Fontanelles / Sutures"
392:– premature fusion of the cranial sutures
746:
434:
348:
245:, which allow movement that facilitates
855:Chemke, Juan; Robinson, Arthur (1969).
667:
665:
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614:Cranial sutures shown from top of head.
14:
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571:Fédération Cynologique Internationale
404:– a buildup of fluid inside the skull
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24:
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561:, is a recognized feature of the
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557:An open fontanelle, known as a
463:Intrauterine growth restriction
934:"FCI Chihuahua breed standard"
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241:. These are joined by fibrous
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1:
873:10.1016/S0022-3476(69)80457-9
729:"Online Etymology Dictionary"
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977:Compound structures of skull
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224:
7:
532:
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32:Fontanelle (disambiguation)
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861:The Journal of Pediatrics
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206:of the sutures is called
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41:
1147:pterygomaxillary fissure
839:MedlinePlus Encyclopedia
819:MedlinePlus Encyclopedia
712:MedlinePlus Encyclopedia
514:
489:Cleidocranial dysostosis
300:cleidocranial dysostosis
798:www.hopkinsmedicine.org
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504:Osteogenesis imperfecta
499:Neonatal hypothyroidism
857:"The third fontanelle"
844:Fontanelles – enlarged
474:Rarer causes include:
440:
323:are also significant.
142:Anatomical terminology
1152:pterygopalatine fossa
717:Fontanelles – bulging
438:
383:intracranial pressure
349:Clinical significance
321:sphenoidal fontanelle
824:Fontanelles – sunken
602:Anterior fontanelle.
567:American Kennel Club
414:Shaken baby syndrome
262:Posterior fontanelle
1142:infratemporal fossa
648:. TheFreeDictionary
286:Anterior fontanelle
215:anterior fontanelle
213:After infancy, the
897:. Terrificpets.com
794:"Craniosynostosis"
781:Waxman, Stephen G.
733:www.etymonline.com
672:Beasley, Melanie.
494:Congenital rubella
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317:mastoid fontanelle
172:anatomical feature
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577:Additional images
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217:is known as the
208:craniosynostosis
178:comprising soft
148:edit on Wikidata
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650:. Retrieved
646:"fontanelle"
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396:Encephalitis
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111:A02.1.00.027
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1183:Neonatology
757:"Fontanels"
590:Fontanelle.
565:breed. The
426:dehydration
176:human skull
76:Identifiers
1167:Categories
1081:sphenoidal
1066:Fontanelle
1014:Stephanion
901:24 October
632:References
408:Meningitis
247:childbirth
237:, and one
180:membranous
160:fontanelle
42:Fontanelle
1076:posterior
1049:posterior
803:4 October
766:3 October
761:Boundless
563:Chihuahua
372:Disorders
225:Structure
168:soft spot
1071:anterior
1039:anterior
1004:Asterion
992:Calvaria
684:24 April
652:24 April
533:Primates
444:Enlarged
355:meninges
319:and the
275:membrane
188:calvaria
170:) is an
164:fontanel
18:Fontanel
1127:dacryon
1086:mastoid
1009:Pterion
881:4241462
738:2 April
680:(CARTA)
547:canines
509:Rickets
377:Bulging
327:Closure
306:bones).
243:sutures
184:sutures
99:D055762
71:Details
1111:Gonion
1106:Nasion
1044:middle
1034:Fossae
1029:Lambda
1024:Bregma
997:Diploë
879:
559:molera
465:(IUGR)
420:Sunken
279:lambda
254:growth
233:, two
219:bregma
196:infant
194:or an
182:gaps (
1178:Skull
1019:Inion
937:(PDF)
920:(PDF)
515:Third
251:brain
192:fetus
190:of a
146:[
135:75437
82:Latin
1120:Both
903:2012
877:PMID
805:2022
768:2016
740:2016
686:2013
654:2013
541:Dogs
294:and
269:and
249:and
162:(or
106:TA98
94:MeSH
869:doi
428:or
130:FMA
123:431
118:TA2
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
