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Peer-reviewedCC BYFrontiers in veterinary science

Cranial fontanelles and the association of bregmatic fontanelle width with cranial morphology in newborn Chihuahua and non-brachycephalic puppies

  • Elina Rautala1
  • Sanna Malkamäki2
  • Tarja S. Jokinen1
  • Junnu Leikola3
  • Mirja Ruohoniemi1
  • Jouni J. T. Junnila4
  • Anna-Mariam Kiviranta1
4 affiliations
  1. 1Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki , ,
  2. 2Pathology Unit, Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki , ,
  3. 3Cleft Palate and Craniofacial Center, Department of Plastic Surgery, University of Helsinki and Helsinki University Hospital , ,
  4. 4EstiMates Oy , ,
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Abstract

Introduction: In adult Chihuahuas, persistent fontanelles are common and have been associated with extreme brachycephaly. It is currently unknown whether persistent fontanelles are congenital bone defects or develop during cranial growth due to bone resorption.

Objectives: We investigated the occurrence of cranial fontanelles, cranial shape, and relative bregmatic fontanelle width in newborn Chihuahuas and non-brachycephalic puppies.

Methods: The study included 50 newborn puppy cadavers. Micro-computed tomography (CT) images of the cranium were used to evaluate occurrence of cranial fontanelles and to measure relative width of the bregmatic fontanelle. Histological samples of the cranium were used to confirm the presence of cranial fontanelles. CT images of the cranium were used to evaluate craniometric ratios, including two different cranial height to cranial base length ratios, cranial height to length, and cranial height to width ratios, and cranial index (CrI). The association of the relative width of the bregmatic fontanelle with craniometric ratios was examined.

Results: 19/19 Chihuahuas and 6/21 non-brachycephalic puppies had cranial fontanelles. All but one puppy had only one fontanelle, which was located at the bregma. The proportion of puppies having at least one cranial fontanelle was higher in Chihuahuas than in non-brachycephalic puppies (p < 0.001). Cranial height to cranial base length ratios, cranial height to length ratio, and CrI were higher in Chihuahuas than in non-brachycephalic puppies (p < 0.001 for each analysis). Bregmatic fontanelle was relatively wider in Chihuahuas than in non-brachycephalic puppies (p = 0.0013) and was associated with higher cranial height to cranial base length 2 (p = 0.022), and cranial height to length ratios (p = 0.023).

Conclusion: Bregmatic fontanelle occurred more frequently in Chihuahuas than in non-brachycephalic puppies, but other cranial fontanelles were uncommon. Our findings suggest that newborn Chihuahuas differ from adult Chihuahuas in which persistent fontanelles are frequently detected. This might indicate that persistent fontanelles located outside bregma may develop during postnatal growth, with bone remodeling and resorption being one possible mechanism. Chihuahuas had brachycephalic cranium already at the time of birth. In newborn puppies, relatively wider bregmatic fontanelle was associated with a shorter and higher cranium, i.e., brachycephalic cranial shape.

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Cite

BibTeXRIS
BibTeX
@article{rautala2026cranial,
  title = {{Cranial fontanelles and the association of bregmatic fontanelle width with cranial morphology in newborn Chihuahua and non-brachycephalic puppies}},
  author = {Elina Rautala and Sanna Malkamäki and Tarja S. Jokinen and Junnu Leikola and Mirja Ruohoniemi and Jouni J. T. Junnila and Anna-Mariam Kiviranta},
  journal = {Frontiers in veterinary science},
  year = {2026},
  month = oct,
  doi = {10.3389/fvets.2026.1922844},
  url = {https://europepmc.org/article/PMC/PMC13727575},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - Cranial fontanelles and the association of bregmatic fontanelle width with cranial morphology in newborn Chihuahua and non-brachycephalic puppies
AU  - Elina Rautala
AU  - Sanna Malkamäki
AU  - Tarja S. Jokinen
AU  - Junnu Leikola
AU  - Mirja Ruohoniemi
AU  - Jouni J. T. Junnila
AU  - Anna-Mariam Kiviranta
PY  - 2026
DA  - 2026/10/20
JO  - Frontiers in veterinary science
DO  - 10.3389/fvets.2026.1922844
UR  - https://europepmc.org/article/PMC/PMC13727575
AB  - Introduction: In adult Chihuahuas, persistent fontanelles are common and have been associated with extreme brachycephaly. It is currently unknown whether persistent fontanelles are congenital bone defects or develop during cranial growth due to bone resorption.  Objectives: We investigated the occurrence of cranial fontanelles, cranial shape, and relative bregmatic fontanelle width in newborn Chihuahuas and non-brachycephalic puppies.  Methods: The study included 50 newborn puppy cadavers. Micro-computed tomography (CT) images of the cranium were used to evaluate occurrence of cranial fontanelles and to measure relative width of the bregmatic fontanelle. Histological samples of the cranium were used to confirm the presence of cranial fontanelles. CT images of the cranium were used to evaluate craniometric ratios, including two different cranial height to cranial base length ratios, cranial height to length, and cranial height to width ratios, and cranial index (CrI). The association of the relative width of the bregmatic fontanelle with craniometric ratios was examined.  Results: 19/19 Chihuahuas and 6/21 non-brachycephalic puppies had cranial fontanelles. All but one puppy had only one fontanelle, which was located at the bregma. The proportion of puppies having at least one cranial fontanelle was higher in Chihuahuas than in non-brachycephalic puppies (p < 0.001). Cranial height to cranial base length ratios, cranial height to length ratio, and CrI were higher in Chihuahuas than in non-brachycephalic puppies (p < 0.001 for each analysis). Bregmatic fontanelle was relatively wider in Chihuahuas than in non-brachycephalic puppies (p = 0.0013) and was associated with higher cranial height to cranial base length 2 (p = 0.022), and cranial height to length ratios (p = 0.023).  Conclusion: Bregmatic fontanelle occurred more frequently in Chihuahuas than in non-brachycephalic puppies, but other cranial fontanelles were uncommon. Our findings suggest that newborn Chihuahuas differ from adult Chihuahuas in which persistent fontanelles are frequently detected. This might indicate that persistent fontanelles located outside bregma may develop during postnatal growth, with bone remodeling and resorption being one possible mechanism. Chihuahuas had brachycephalic cranium already at the time of birth. In newborn puppies, relatively wider bregmatic fontanelle was associated with a shorter and higher cranium, i.e., brachycephalic cranial shape.
SN  - 2297-1769
ER  -