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Embryology, Anatomy, Normal Findings, and Imaging Techniques

Embryology A detailed study of the development of the ear is beyond the scope of this chapter; only the key embryologic events and their timing are discussed here. It is important to appreciate that the inner ear is derived from the neuroectoderm, whereas the middle ear and the external ear develop from the branchial apparatus, explaining why the abnormalities of the inner ear are generally isolated…

Nose and Sinonasal Cavities

Development and Anatomy of the Nose and Sinonasal Cavities The craniofacial structures form from a complex sequence of events dictated by molecular changes during the third to 10th gestational weeks. The nose forms in the fourth gestational week from the frontonasal processes and two nasal placodes that develop dorsal to the stomodeum. The nose derives from ectoderm, mesoderm, and a deep cartilaginous capsule. The posterior nasal…

Orbital Neoplasia

A wide variety of primary and secondary neoplasms may affect the orbit. Most orbital masses are benign and slow growing, but approximately 20% are malignant. Making the correct diagnosis may be difficult for several reasons. In children, it may be challenging to obtain an accurate history and physical examination. The presenting symptoms (and imaging findings) of different pathologic entities may overlap considerably. Nonneoplastic masses may present…

Orbit Infection and Inflammation

A wide variety of disease processes can cause inflammatory changes in the orbit, including infection, idiopathic inflammation, granulomatous disease, thyroid-related disease, optic neuritis, and sickle cell disease. Additionally, metabolic diseases can also affect the optic nerves, leading to vision loss. Many of these disease processes can share a similar imaging appearance, and consequently a good understanding of their pathophysiology and clinical presentation is needed to formulate…

Prenatal, Congenital, and Neonatal Abnormalities

Assessment of the orbits is part of a detailed fetal sonographic or magnetic resonance imaging (MRI) scan, particularly in the setting of suspected central nervous system malformation. When further assessment is performed by fetal MRI, obvious ocular pathologies can be missed, particularly if they are bilateral and symmetric. Diagnoses can be further honed or even altered completely when a coexisting ocular pathology is found. Ocular evaluation…

Embryology, Anatomy, Normal Findings, and Imaging Techniques

Embryology of the Eye Development of the eye originates from neuroectoderm, surface ectoderm, and neural crest cells. The neuroectodermal layer gives rise to the retina, iris, and optic nerve; the surface ectoderm gives rise to the lens; the neural crest cells are responsible for vascular structures, sclera, choroid, and mesenchymal tissue from which the adnexal structures, bony orbit, fat, and nerve sheaths arise. The prime regulatory…

Complications of Contrast Media

Allergic-Like Reactions Introduction Contrast media (CM) are an essential aid in diagnostic medical imaging. They are used primarily to enhance the visibility of blood vessels, organs, and pathology in the body. CM are considered pharmacologic agents, and, like any other medication, they are not without adverse effects. Incidence Scant data are available regarding the incidence of contrast reactions in children for at least three reasons: (1)…

Magnetic Resonance Safety

Magnetic resonance imaging (MRI) has proved to be a powerful diagnostic imaging tool in children and adults. MRI uses low-energy nonionizing radio waves, and as such it is particularly well suited for pediatric and longitudinal imaging studies. MRI exploits a wide variety of intrinsic tissue-specific properties to generate a wide spectrum of tissue contrast, thus providing detailed information about anatomy, physiology, and function. For clinical MRI…

Radiation Bioeffects, Risks, and Radiation Protection in Medical Imaging in Children

Diagnostic imaging has evolved from the single technique of radiography discussed in the first edition of Caffey's Pediatric X-Ray Diagnosis in 1945 to a specialty with many modalities and techniques. Many of these modalities use ionizing radiation, and some, such as computed tomography (CT) and nuclear imaging, entail relatively high doses of radiation. Therefore the imaging community (and our medical colleagues) must jointly adhere to two…

Artifacts, Pitfalls, and Normal Variants

When I began my involvement with diagnostic sonography nearly 4 decades ago, this chapter would have been considered ludicrous. Virtually all of sonography was considered to be either an artifact or a pitfall. Clinicians did not take this modality seriously, and few critical decisions were ever based on the results of the ultrasound examination alone. With time, improvements in both technology and our understanding of normal…