Illustrated Encyclopedia of Human Anatomic Variation: Opus V: Skeletal Systems: Cranium

Frontal Bone

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed

The frontal sinuses may be absent, small, or remarkably large, extending through orbital bones, zygomatic processes, and into the squamae.

The coronal suture may be absent. Persistence of the interfrontal or metopic suture has reported frequences ranging from 1 to 12% of skulls. Metopism occurs, according to one study, in 8.7% of European Caucasians, 5.1% of Asians, 1.2% of blacks, and in only 1% of Australian Caucasions. Sutural or intercalated interfrontal ossicles may also be present. In another study, persistence of the complete frontal suture (metopism) occurs more frequently in the East Asian and American white groups (9%) than in the American Negro (1%), whereas traces were found to occur with the following frequencies: East Asian, 12%; American Negro, 8%; American white, 2% (Woo, 1949a)

Persistence of a complete or incomplete frontal (metopic) suture may be associated with a syndrome involving several variations of the visceral cranium and the phalanges. Failure of ossification in a broad and elongated area in the region of the frontal suture has been shown to be associated with a partial or complete absence of the clavicle (cleidocranial dysostosis).

A thicking of the internal lamina of the squama (hyperostosis frontalis interna) and orbital part of the frontal bone is found almost exclusively in women (about 98%). Hyperostosis frontalis interna may extend into the diploë but does not involve the external lamina or the posterior wall of the frontal sinus.

A frontal spine may be present, which can be mistaken for a perpendicular plate of the ethmoid.

Foramen Vesalii. Cranial Variations.

Metopic Suture.

Metopic Suture.

Variations in Frontal and Maxillary Sinuses.

References

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