At what age do mastoid (mastoid air cells) spaces develop, and are they present in 4-month-old infants?

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Last updated: April 9, 2025 • View editorial policy

From the Research

Mastoid spaces begin to form at birth but are not fully developed until later in childhood, and in a 4-month-old infant, the mastoid spaces are present but still very rudimentary. The development of the mastoid air cell system is a gradual process that starts from the antrum, with minimal pneumatization at birth 1. As the child grows, the air cells expand from the mastoid antrum into the surrounding temporal bone, creating the honeycomb-like structure seen in adult mastoids. The significant development of the mastoid air cell system begins around 2 years of age and continues through adolescence, with full pneumatization typically achieved by puberty 2. In 4-month-old infants, while the mastoid antrum is present, the extensive network of air cells characteristic of adult mastoids has not yet developed. This developmental timeline is important clinically because the limited pneumatization in infants affects how ear infections may spread and how certain ear surgeries are approached. For instance, the risk of acute mastoiditis, although rare in infants under 6 months, can be a serious complication of otitis media, highlighting the need for prompt diagnosis and treatment 3. The clinical presentation and management of such conditions are influenced by the developmental stage of the mastoid air cell system, underscoring the importance of understanding this process in the context of pediatric otolaryngology. Given the potential for serious complications, it is crucial to consider the developmental stage of the mastoid when evaluating and treating ear infections in infants, emphasizing the need for careful clinical assessment and appropriate imaging studies when necessary 4, 5.

References

Research

MRI findings of the middle ear in infants.

Acta oto-laryngologica, 2007

Research

Acute Mastoiditis in Children: Necessity and Timing of Imaging.

The Pediatric infectious disease journal, 2016

Research

Acute mastoiditis in infants.

European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery, 2006

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