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Cranial Synchondroses

Cranial synchondroses are cartilaginous joints between the bones of the base of cranium that ensure its growth in length and width. With age, these synchondroses gradually ossify, becoming synostoses. Similar processes of growth cessation and ossification occur with the cranial sutures. Thus, by the age of 70, the skull of most individuals becomes a single bone1.

In children and adolescents, the following cranial synchondroses can be observed:

manicula

The anterior and posterior intra-occipital synchondroses (synchondrosis intraooccipitalis anterior et posterior) fully ossify by the age of 7–92, allowing for the expansion and elongation of the posterior cranial fossa until then.

  • 1 Wang M, Haveles C, et al. The 27 facial sutures: timing and clinical consequences of closure. Plast Reconstr Surg, 2022, 149(3):701–720.
  • 2Madeline L, Elster A. Suture closure in the human chondrocranium: CT assessment. Radiology, 1995, 196(3):747–756.
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    Fissures of the cranial base Synchondroses of external surface of the cranial base
    Basis cranii externa
    By clicking on the image, you will hide all the cranial synchondroses and see the fissures in their place, as seen on dry skull specimens.
    When examining the external base of the skull on anatomical lab specimens, it’s easy to notice how uneven and rough it is, especially around the petrous part of the temporal bones near the foramen lacerum. In life, the fissures surrounding petrous parts are filled with cartilage, making the skull base much smoother in vivo.
    Terminologia Anatomica
    Synchondrosis sphenooccipitalis Spheno-occipital synchondrosis
    Synchondrosis sphenopetrosa Sphenopetrosal synchnodrosis
    Synchondrosis petrooccipitalis Petro-occipital synchondrosis
    Foramen ovale Foramen ovale
    Foramen spinosum Foramen spinosum
    Canalis carotis Carotid canal
    Foramen jugulare Jugular foramen
    Foramen stylomastoideum Stylomastoid foramen
    Fissura sphenopetrosa Sphenopetrosal fissure
    Fissura petrooccipitalis Petro-occipital fissure
    Foramen lacerum Foramen lacerum
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    Spheno-occipital synchondrosis Spheno-occipital synostosis
    Synchondrosis et synostosis sphenooccipitalis
    Click on the image to switch the depiction of the spheno-occipital synchondrosis to spheno-occipital synostosis. The ossification process typically completes by the age of 17–181,2, thereby ending the growth of the cranial base in length. The bone complex formed by this fusion is sometimes called the basilar bone (os basilare)3.
    Terminologia Anatomica
    Os sphenoideum Sphenoid bone
    Os occipitale Occipital bone
    Synchondrosis sphenooccipitalis Spheno-occipital synchondrosis
    Synostosis sphenooccipitalis Spheno-occipital synchondrosis
    Os basilare Basilar bone
  • 1 Giap H, Wen X, et al. Physiologic timeline of cranial-base suture and synchondrosis closure. Plast Reconstr Surg, 2021, 148(6):973e–982e.
  • 2 Bassed R, Briggs C, et al. Analysis of time of closure of the spheno-occipital synchondrosis using computed tomography. Forensic Sci Int, 2010, 200(1–3):161–164.
  • 3 Привес М, Лысенков К, Бушкович В. Анатомия человека. 1985, 9–е изд. Москва «Медицина» с.113.
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    Petro-occipital synchondrosis Petro-occipital synostosis
    Synchondrosis petrooccipitalis
    The petro-occipital synchondrosis persists longer than other synchondroses at the base of the skull. Its final ossification is rarely completed in individuals under 60. Some researchers link hearing loss in the elderly to the ossification of the petro-occipital synchondrosis, as this process is associated with the loss of the conductive properties of the temporal bone and disruption of cerebrospinal fluid circulation through the cochlear aqueduct*.
    Terminologia Anatomica
    Os temporale Temporal bone
    Pars petrosa Petrous part
    Pars basilaris ossis occipitalis Basilar part of the occipital bone
    Synchondrosis petrooccipitalis Petro-occipital synchondrosis
  • * Balboni A, Estenson T, et al. Assessing age-related ossification of the petro-occipital fissure: laying the foundation for understanding the clinicopathologies of the cranial base. Anat Rec A Discov Mol Cell Evol Biol, 2005, 282(1):38–48.
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    Sphenoethmoidal synchondrosis Sphenoethmoidal synostosis
    Synchondrosis et sutura sphenoethmoidea
    Ossification of the sphenoethmoidal synchondrosis is completed by the age of 5. Afterward, a small groove, externally resembling a cranial suture, can sometimes be found in place of the synchondrosis. Although this groove is not strictly a syndesmosis, it is referred to by analogy with true cranial sutures as the sphenoethmoidal suture (sutura sphenoethmoidea)*.
    Terminologia Anatomica
    Synchondrosis sphenoethmoidea Spheno-ethmoidal synchondrosis
    Os sphenoideum Sphenoid bone
    Os ethmoideum Ethmoid bone
    Sutura sphenoethmoidea Spheno-ethmoidal suture
  • * Feneis H, Dauber W. Pocket atlas of human anatomy. Based on the international nomenclature. 4th ed. Thieme, Stuttgart, New York, 2000
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    First published: 16/Oct/2024