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Growth of the Cranial Base HHiH
Published in D. Dixon Andrew, A.N. Hoyte David, Ronning Olli, Fundamentals of Craniofacial Growth, 2017
They showed vault changes predicted from these rules, which can be extended to certain basicranial changes. For example, in symmetrical bilateral coronal stenosis, the frontal and parietal bones fuse to form a single bone plate. This fusion also involves the coronal ring, sphenofrontal and sphenoethmoidal sutures in the anterior fossa. In the vault there is increased growth in the sagittal suture which, with increased bisquamosal growth, gives a wider posterior calvarium with bitemporal bulging and increased metopic separation with symmetrical frontal bossing. Because of the metopic widening, there is also a transversely wider anterior fossa, with a greater interorbital distance and hypertelorism. Enhanced resorption in the anterior fossa not only increases forehead bossing and interorbital separation, but tilts the sphenoid wings, makes the orbit shallower, and can lead to a rotation of the maxilla in the orbital floor, all of which contribute to exorbitism (see Chapter 10 for other features of coronal synostosis). Slomic et al. (1992b) recorded overall decreases of skull length in bicoronal synostosis with shortening of sagittal measures, the nasion-tuberculum sellae-basion, and depression (flattening) of the basal angle.
A giant dermoid cyst of the orbit
Published in Orbit, 2019
Bipasha Mukherjee, Akruti Desai
Dermoid cysts are thought to be ectodermal rests “pinched-off” at bony suture lines. The sequestered tissue forms a cyst lined with keratinized epithelium and dermal elements. They can be classified into juxtasutural, sutural, and soft-tissue types.4 The most common is the juxtasutural type and in the orbit is chiefly located at the zygomatico-frontal suture. Clinically, they present as firm, smooth, partially immobile masses. These lesions can generally be excised without difficulty. Orbital dermoids are divided as superficial, or deep, based on their relationship to orbital septum.2 Deep lesions are more insidious, and often develop at the sphenozygomatic or sphenoethmoidal suture. Deferral of orbital surgery has often been advocated in deep dermoid cysts, given the slow growing nature of most cysts.5 On occasion, a deep orbital dermoid cyst may require a lateral orbitotomy for intact removal.6–9 The term “giant orbital dermoid” has been used to describe an orbital cyst, equal in size to or larger than the affected eye.7 This tumor has no predilection for sex or race.10 Giant orbital dermoid was first reported by Reim et al. who demonstrated limitation of ocular motility secondary to compression.11 Later, two cases of giant orbital dermoid cysts which presented in adults have been reported.7 These cysts were completely removed with recovery of visual function and ocular motility. But this is not always possible. In the case described by Bickler-Bluth et al., the cyst contents extruded intraoperatively during release of adhesions.6 Recurrence of an orbital dermoid in infancy has been reported by Leonardo et al. in a child who had well-preserved ocular anatomy but developed visual impairment due to dense amblyopia.8 A case of a neglected giant orbital dermoid in a Nigerian infant has been reported. This child underwent a lid sparing exenteration at 2 years of age. Early presentation and surgical intervention has been advocated as the key to good outcome in this group of patients.12 Hou et al. have radiographically quantified the growth rate of a deep orbital dermoid cyst in a child demonstrating a 205% increase in length at a relatively constant rate over a 23 month observational period.13 Left untreated they can lead to complications like cyst rupture, optic neuropathy, expansion into temporal fossa, or even intracranial extension. Salvage of the globe is possible with smaller lesions. Rarely, when dermoid cysts may rupture in vivo, they present with a picture simulating idiopathic orbital inflammation or orbital cellulitis. When a part of the cyst is in orbit and a part extends into temporal fossa, it assumes a dumbbell configuration and presents with pulsating proptosis with mastication.14