Sella Bridging
From bonepath
Ossification of the ligaments about the pituitary fossa are commonly referred to as “sella [turcica] bridging,” and have a few different manifestations. Fusion of the sphenoid anterior and middle clinoid processes results in the bony enclosure of the internal carotid artery, forming a caroticoclinoid foramen. A complete sellar bridge or ‘roof’ occurs when the pituitary diaphragm and/or the interclinoid ligament (between the anterior and posterior clinoid processes) ossify. In the case of a complete bridge, there is still a foramen superiorly for the transmission of the pituitary stalk, as well as foramina laterally for communication with the adjacent cavernous sinus (Kantor and Norton 1989); hence “roof” is a somewhat misleading term. All crania in the Ford collection that exhibit a complete sellar bridge also display the caroticoclinoid foramen.
The etiology of sella bridging is unclear, as the feature could occur idiosyncratically or as the result of some underlying pathology. Some studies have found a higher frequency of bridging in patients who also display facial and dental abnormalities. Leonardi and colleagues (2006) report a significantly higher incidence of sellar bridging in patients with either second molar agenesis or a palatally displaced canine, than in controls with normal dentition. Jones and coworkers (2005) reported a higher incidence of bridging in patients whose dental malocclusion was treated surgically rather than orthodontically. Becktor and colleagues (2000: 72) found a higher incidence of bridging in patients with “severe craniofacial deviations,” namely under- or overbite. Finally, bridging is a common symptom in patients with Axenfeld-Rieger Syndrome (ARS), an autosomal-dominant disorder which manifests clinically in ocular defects, and maxillary and dental hypoplasia (Becktor et al. 2000, Meyer-Marcotty et al. 2008). In patients with ARS, sella turcica bridging is also associated with a steepened medullary clivus; these two features are present in cranium 96-11-050.
Just as the causes of sellar bridging are unclear, so too is it debatable whether the feature results in clinical issues. The only major issues detectable from the literature are pains due to compression of nearby nerves and arteries (e.g. internal carotid artery). In addition, the presence of a bony bridge complicates surgical removal of the anterior clinoid process in treatment of aneurysm (Ozdogmus et al. 2003, Erturk et al. 2004, Peker et al. 2006).
[edit] Examples from Ford Collection
[edit] References
Becktor JP, Einersen S, Kjaer I. 2000. A sella turcica bridge in subjects with severe craniofacial deviations. Eur J Orthod 22:69-74
Erturk M, Kayalioglu G, Govsa F. 2004. Anatomy of the clinoidal region with special emphasis on the caroticoclinoid foramen and interclinoid osseous bridge in a recent Turkish population. Neurosurg Rev 27:22-6
Hauser G, De Stefano GF. 1989. Epigenetic variants of the human skull. Lubrecht & Cramer Ltd
Idrees F, Bloch-Zupan A, Free SL, Vaideanu D, et al. 2006. A novel homeobox mutation in the PITX2 gene in a family with Axenfeld-Rieger syndrome associated with brain, ocular, and dental phenotypes. Am J Med Genet B Neuropsychiatr Genet 141B:184-91
Jones RM, Faqir A, Millett DT, Moos KF, McHugh S. 2005. Bridging and dimensions of sella turcica in subjects treated by surgical-orthodontic means or orthodontics only. Angle Orthod 75:714-8
Kantor ML, Norton LA. 1987. Normal radiographic anatomy and common anomalies seen in cephalometric films. American Journal of Orthodontics and Dentofacial Orthopedics 91:414-26
Leonardi R, Barbato E, Vichi M, Caltabiano M. 2006. A sella turcica bridge in subjects with dental anomalies. Eur J Orthod 28:580-5
Meyer-Marcotty P, Weisschuh N, Dressler P, Hartmann J, Stellzig-Eisenhauer A. 2008. Morphology of the sella turcica in Axenfeld-Rieger syndrome with PITX2 mutation. J Oral Pathol Med 37:504-10
Ozdogmus O, Saka E, Tulay C, Gurdal E, et al. 2003. Ossification of interclinoid ligament and its clinical significance. Neuroanatomy 2:25-7 Peker T, Anil A, Gülekon N, Turgut HB, et al. 2006. The incidence and types of sella and sphenopetrous bridges. Neurosurg Rev 29:219-23
