// Workers AI · dad joke modeWhat did the molera say? I'm a little cracked.
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A molera (also known as a fontanel) is a "soft spot" on the top of a Chihuahua's skull; it is the equivalent to the bregmatic or anterior fontanelle in human babies, but unlike most mammals, a Chihuahua's fontanelle persists into maturity. Historically it has been very common amongst Chihuahuas and was regarded as a mark of purity for this miniature dog breed. It is still mentioned in many Chihuahua breed standards; however, it is considered a fault in European countries because of concern that this might reflect underlying malformations such as hydrocephalus and ventriculomegaly, Chiari-like malformation and syringomyelia. Fontanelles are fibrous, membrane-covered gaps that lie between the skull bones and at the intersection of the cranial sutures. The cranial sutures are the junctions between cranial (or skull) bones. The fontanelles serve as the major sites of bone expansion during post-natal skull growth which accommodates the enlarging brain. The Chihuahua likely has a molera because of neuroparenchymal disproportion (i.e. a proportionally big brain for the skull). This is likely because there is premature closure of the skull base cranial sutures (brachycephaly due to craniosynostosis). To accommodate the developing brain there is increased growth of the skull bone in a parallel plane giving the dog a characterised domed or "apple-headed" appearance.
A Finnish study by the University of Helsinki along with the University of Surrey found that the increased number and size of persistent fontanelles in Chihuahuas were associated with small body size, syringomyelia (fluid filled cavities in the spinal cord), ventriculomegaly (i.e. enlargement of the lateral ventricles), and craniocervical junction abnormalities. This challenges the belief that a molera is a clinically irrelevant finding not associated with other structural abnormalities.[1]
References
[edit]- ↑ Kiviranta AM, Rusbridge C, Lappalainen AK, Junnila JJ, Jokinen TS (July 1, 2021). "Persistent fontanelles in Chihuahuas. Part II: Association with craniocervical junction abnormalities, syringomyelia, and ventricular volume". Journal of Veterinary Internal Medicine. 35 (4): 1848–1856. doi:10.1111/jvim.16123. ISSN 1939-1676. PMC 8295681. PMID 33939205.
- Green CE, Braund KG (1989). "Diseases of the brain". In Ettinger SI (ed.). Textbook of veterinary internal medicine. Philadelphia: WB Saunders. p. 584.
- Rivers WJ, Walter PA (1992). "Hydrocephalus in the Dog: Utility of Ultrasonography as an Alternate Diagnostic Imaging Technique". Journal of the American Animal Hospital Association. 28: 578–623.