Orbit Intro, Congenital Deformities, Cranio-Orbital Defects

Axial

imaging plane that is along the horizontal plane.

Coronal

imaging plane that is along the vertical plane, separating the body from front to back

Sagittal

imaging plane that is along the vertical plane, separating the body from left to right

Computed tomography (CT)

a scan which is a series of X-rays taken at different angles to create cross sectional images. Has the ability to image a wide variety of structures including bone, soft tissues, tumors, vasculature, etc.

Fast

High detail (thin slices)

Cost effective

Less sensitive to movements

four Benefits of CT Scan

radiation exposure

reaction to contrast dye

fetal exposure

not sensitive to inflammation of meninges

four Disadvantages of CT Scan

dense

White areas of a CT scan represent ____ tissue such as bone or metal

less dense

Grey areas of a CT scan represent less dense tissue such as fat or water

Magnetic resonance imaging (MRI)

a scan which uses magnetic and radio waves for detailed 3D imaging of the body. Has the ability to image a wide variety of structures including bone, soft tissues, organs, etc. Avoid in cases of metallic foreign bodies.

No radiation

High detail

Low risk of allergy

3 Benefits of MRI Scan

cannot use w implantable devices

cannot use in nursing women

slow

costly

fetal exposure

difficulty differentiating tumors and edema

six Disadvantages of MRI Scan

T1

MRI sequence that highlights locations of fat using gadolinium for contrast.

T2

MRI sequence that highlights locations of water.

FLAIR

MRI sequence that is similar to T2, but suppresses free water as seen in normal cerebrospinal fluid

Diffusion

MRI sequence used for tumor characterization and cerebral ischemia

Anophthalmos

a rare, complete failure of optic vesicle development occurring week 1-3 of embryological development. Can result in the disruption of development of other ocular structures including the orbit, lacrimal gland, lids, etc.

Microphthalmos

an arrest of ocular growth (unilateral or bilateral) leading to total axial length 2+ standard deviations below the age similar controls. Results from a developmental problem of the globe at any stage of growth of the optic vesicle after week 4 of embryological development.

Simple

form of microphthalmos occurring without other ocular malformations

Complex

form of microphthalmos occurring with a coloboma, usually of the iris.

Cystic

form of microphthalmos occurring with a cyst.

Hypertelorism

an abnormally large pupillary distance.

Hypotelorism

an abnormally small pupillary distance.

Craniosynostosis

premature fusion of one (more common) or more of the cranial sutures resulting in malformation of the head shape. Can occur independently or as part of a syndrome.

12-18

Cranial sutures will normally fused around ____ months of age

Misshapen head

impaired brain development

increased intracranial pressure

orbital deformities

four complications of craniosynostosis.

Scaphocephaly (MOST COMMON)

premature sagittal suture fusion resulting in the elongation of the skull in the anterior-posterior direction leading to a bossing of the forehead. Is more common in boys (4:1)

Trigonocephaly (SECOND MOST COMMON)

premature metopic (frontal) suture fusion resulting in a high, retreating, triangular forehead. Is also associated with hypotelorism due to migration of the eyes following cranium growth.

Brachycephaly

premature fusion of the coronal sutures resulting in the shortening of the skull in the anterior-posterior direction.

Plagiocephaly

premature unilateral fusion of all cranial sutures on a single side of the head resulting in a flattening of one side of the skull producing a rhomboid shape.

Oxycephaly

Premature fusion of all cranial sutures resulting in a cone shaped skull. Is the most severe form of craniosynostosis.

Orbital dystopia

a vertical misalignment of the orbit which can be congenital (craniosynostosis) or acquired via trauma or mass of the orbit.

11-24 mm

normal range of exophthalmos

18 mm

average Asian exophthalmos value

20 mm

average Caucasian exophthalmos value

24 mm

average African American exophthalmos value

2

Any difference of exophthalmos values between the two eyes greater than ___ mm should be investigated

Couzon's disease

the most common cranio-facial syndrome occurring due to mutation of the fibroblast growth factor gene (FGFR2) or by spontaneous mutation 50% of the time. Begins in the first year and completes by the 2nd to 3rd year. Involves brachycephaly, underdevelopment of the maxillary and zygomatic bones, wide cranium, hearing loss, and V shaped palate. Characteristic "frog like face".

Goldenhar syndrome (oculo auricular vertebral dysplasia)

syndrome involving malformation of the ear, eye, and vertebra. Is the second most common cranio-facial syndrome. Appears as a triad of craniofacial microsomia, spinal abnormalities, and ocular dermoid cyst. Is more common in males (3:2).

Mandibulofacial dystoses (Franceschetti syndrome, Treacher Collins syndrome)

a craniofacial syndrome caused by an autosomal dominant mutation of the TCOF1 gene resulting in hypoplasia of the zygomatic, maxillary, and mandibular bones. Is also commonly associated with underdevelopment of the ear and hearing, cleft palate, and airway problems. May or may not have impaired intelligence.

Hallerman Streiff syndrome (Oculomandibulodyscephaly)

a rare craniofacial syndrome caused by spontaneous or autosomal recessive mutation. Results in a "bird face" and other facial abnormalities.

Apert's syndrome

craniofacial syndrome involving brachycephaly, oxycephaly, high cleft palate, organ anomalies, mental handicap, and syndactyly.

Supportive therapy, strabismic therapy, epilation

three ocular treatments of cranio-facial syndromes

Meningocele

a rare, congenital neural tube defect resulting in meninges and CSF protruding through the orbit usually through a bony defect, and sometimes through a natural opening. Can be anterior or posterior variety.

Encephalocele

a rare, congenital neural tube defect resulting in a sac like protrusion of the meninges, CSF, and grey matter through an opening in the skull. Can be anterior or posterior variety. Is more common in females than in males. The more neural tissue that is herniated, the worse the prognosis of the condition is.

Mucocele

an acquired defect involving erosion of the orbital wall caused by mucoid secretions and epithelial debris seen in infection, trauma, allergy, or tumor. Ocular signs include proptosis, periocular edema, diplopia, and epiphora.

Cyclopia/synophthalmia

a rare failure of the prosencephalon to divide the orbits into two separate cavities. The paired ocular structures then become one central orbit where the nose is often missing. Incompatible with life.