Orbital Cavity: Developmental Anomalies

Developmental Anomalies

Congenital developmental anomalies affecting the orbital cavity are very rare.

Craniofacial Dysplasia

Craniostenosis

This clinical picture involves premature fusion of the cranial sutures. Clinical signs often include bilateral exophthalmos associated with ocular hyper-telorism and exotropia (divergent strabismus). The mechanical impairment of the optic nerve is evidenced by development of papilledema and requires sur-gical decompression to prevent atrophy of the optic nerve.

Oxycephaly

Premature fusion of the coronal suture causes the orbits to become ele-vated, flattened, and smaller than normal.

Craniofacial Dysostosis

Premature fusion of the coronal and sagittal sutures also results in a highskull and abnormally small orbits. This condition is also characterized by a wide root of the nose and a prominent chin.

Enucleation in early childhood can result in orbital hypoplasia as the globe provides a growth stimulus for the orbital cavity. Therefore the patient should promptly receive a prosthesis.

Mandibulofacial Dysplasia

Oculoauriculovertebral Dysplasia

Epibulbar dermoids near the limbus are present in addition to outer earanomalies and rudiments of a branchial passage in the cheek (see Fig. 4.19)

Mandibulofacial Dysostosis

Also known as Treacher Collins’ syndrome (incomplete type) or Frances-chetti’s syndrome (complete type), this anomaly of the first branchial arch is characterized by orbital deformities with antimongoloid palpebral fissures, coloboma of the lower eyelid, low-set ears, and a hypoplastic mandible withdental deformities.

Oculomandibular Dysostosis

In addition to the typical bird-like face, this anomaly may be accompanied by bilateral microphthalmos associated with cataract, nystagmus, and stra-bismus.

Rubinstein–Taybi Syndrome

This craniomandibulofacial dysplasia is primarily characterized by antimon-goloid palpebral fissures, ocular hypertelorism, epicanthal folds, and enoph-thalmos. Cataracts, iris colobomas, and infantile glaucoma have also been described.

Meningoencephalocele

Incomplete fusion of the cranial sutures in the orbital region can lead toevaginations of dural sac with brain tissue. Clinical findings occasionally include pulsating exophthalmos or, in extreme cases, a tumorous protrusion.

Ultrasound studies: 

Two techniques are available for this noninvasiveexamination.

The B-mode scan (B stands for brightness) provides a two-dimensionalimage of orbital structures. This examination is indicated in the presence ofsuspected orbital masses.

The A-mode scan (A stands for amplitude) permits precise measurement ofoptic nerve and muscle thickness. This examination is indicated as a follow-up study in the presence of Graves’ disease (endocrine orbitopathy).

These studies may also be combined with Doppler scans to evaluate blood flow.

Conventional radiographic studies: 

These studies usually only provideinformation about the nature of bone structures, i.e., whether a fracture is present and where it is located. Smaller fractures often cannot be diagnosed by conventional radiography and require CT scans.

Computed tomography and magnetic resonance imaging: 

These modernexamination modalities can precisely visualize orbital structures in various planes. They are standard methods for diagnosing tumors.

In the presence of orbital trauma, initial CT studies should be per-formed as this method can better visualize bony structures. Initial MRI scans should be performed where soft-tissue lesions are suspected.

Angiography: 

This is indicated in the presence ofsuspected arteriovenousfistulas.

Osteopathies

Many of these disorders can produce orbital changes. The most common of these diseases include Paget’s disease of bone, dysostosis multiplex (Hurler’s syndrome), and marble-bone disease of Albers-Schönberg in which compres-sive optic neuropathy also occurs.