Central nervous system (CNS) anomalies occur in 1.4 to 1.6 per 1,000 live births and 3% to 6% of still births. Whereas some anomalies can be detected as early as the first trimester (such as anencephaly), others may not develop or become apparent until later in gestation. Ultrasound is the initial imaging modality used for the assessment of fetal CNS anomalies. When ultrasound is carefully performed…
Perfusion Imaging In the cerebrovascular literature, perfusion imaging refers to an all-encompassing term of various methods to measure hemodynamically derived functional parameters in the brain. In radiology, the three most common parameters that are assessed and utilized clinically are cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT). CBV refers to the amount (volume) of blood within a given mass of brain…
Physiologic Basis of Functional Magnetic Resonance Imaging Functional magnetic resonance imaging (fMRI) is based on the blood oxygen level–dependent (BOLD) contrast effect and neuronal activity–cerebrovascular flow coupling. Oxygenated blood (oxyhemoglobin) is diamagnetic, producing little susceptibility-related dephasing on magnetic resonance (MR) signal. Deoxyhemoglobin is paramagnetic and elicits a more prominent effect on local field homogeneity and phase coherence, resulting in signal loss. Changes in the relative concentrations…
Of the advanced magnetic resonance imaging (MRI) modalities, diffusion-weighted (DW) MRI has probably garnered the most excitement in both clinical and research settings during the past decade. Standard now in nearly every neuroimaging MR protocol, DW-MRI has demonstrated substantial clinical utility in the detection of acute ischemia, the differential diagnosis of intracranial lesions, and the evaluation of white matter. Diffusion tensor imaging (DTI) and other high-angular…
Magnetic resonance spectroscopy (MRS) capability is available in most clinical magnetic resonance (MR) scanners. The additional information from MRS allows the assessment of cellular metabolism noninvasively. For the brain in particular, it has been proved that MRS of protons or hydrogen (1H MRS) provides additional clinically relevant information for several disease processes such as brain tumors, metabolic disorders, and systemic diseases, and it is the most…
The human brain undergoes four phases of development: (1) dorsal induction (primary and secondary neurulation), (2) ventral induction (patterning of the forebrain), (3) neuronal proliferation and migration, and (4) myelination. During the third week of embryogenesis, initiation of the central nervous system evolves with the development of the notochordal process. This derivative of ectoderm grows rapidly in length so that by 20 days it is converted…
Congenital Depressions Congenital depressions of the calvaria result from mechanical factors that occur before or during birth. During labor, calvarial depressions are caused by excessive localized pressure on the head by the bony prominences in the maternal pelvis, including the sacral promontory, pubic symphysis, and sciatic spines ( e-Fig. 23.1 ). Application of forceps to the fetal head and traction with excessive force is another less…
Anatomy At birth, the mandible consists of two lateral halves united in the midline at the symphysis by a bar of cartilage ( Fig. 22.1 , e-Fig. 22.2 , and Fig. 22.3 ). Bony fusion of the symphysis usually occurs before the second year, but segments of the fissures may persist beyond puberty. The body of the mandible is large at birth compared with the relatively…
Primary Neoplasms Primary neoplasms of the skull are rare. The most common lesions in children with a solitary nontraumatic lump on the head are dermoid tumors (61%), cephalhematomas (9%), Langerhans cell histiocytosis (LCH) (7%), and occult meningoceles and encephaloceles (4%). Osteochondromas may arise from the cartilaginous bones of the skull base. Osteoblastomas have been reported in the calvaria of infants, and aneurysmal bone cysts have been…
The clinical and radiologic features of craniosynostosis result from lack of sutural formation or premature fusion across membranous sutures. The premature sutural closure prevalence is displayed in e-Table 20.1 . Normal sutures permit skull growth perpendicular to their long axes. With early closure of one suture, there is compensation and excess growth in others resulting in a craniofacial deformity ( e-Table 20.2 ; e-Fig. 20.1 and…
The fetal abnormalities described in this chapter are those most likely to be assessed by a pediatric radiologist who primarily performs fetal magnetic resonance imaging (MRI), computed tomography (CT), radiography, and ultrasound. These additional modalities are particularly useful for acquiring further characterization of fetal abnormalities, especially when a fetal autopsy will be declined but a couple needs to be counseled regarding future pregnancies. In most of…
Anatomy of the Skull The skull is divided into three portions: the neurocranium, the face, and the base. The neurocranium is composed of the membranous portions of the occipital, parietal, frontal, and temporal bones, and is bounded inferiorly by the base of the skull, which includes the sphenoid and ethmoid bones. The face is between the forehead and chin. Routine skull radiographs include the frontal projection,…
Thyroid Gland Embryology The name “thyroid” is derived from the Greek word for shield due to the gland's shape and relationship with the laryngeal thyroid cartilage. The human thyroid gland has a dual embryonic origin. The two thyroid cell types, follicular cells (thyrocytes) and parafollicular (C-cells), are derived from all three germ cell layers. The most abundant cells, the follicular cells, arise from the thyroid anlage.…
Cancer is a leading cause of death during childhood, second only to trauma in children between the ages of 5 and 14 years. Head and neck involvement can be seen in up to 12% of childhood cancers. Lymphoma (50%) and rhabdomyosarcoma (30%) account for the majority of primary malignant pediatric head and neck tumors. Other malignant head and neck tumors include thyroid carcinoma, nasopharyngeal carcinoma, other…
Primary inflammatory processes in the pediatric neck are common, and contrast-enhanced computed tomography (CT) allows for characterization of the involved spaces, detecting complications, and determining appropriate clinical management. Pharyngotonsillitis and Peritonsillar Abscess Overview. Acute infectious pharyngitis and tonsillitis are common and do not require imaging for diagnosis. However, when a peritonsillar abscess is suspected, imaging is used for diagnosis and to guide management. Etiology. Most pharyngitis…
Congenital lesions of the neck consist of a variety of entities, some of which become apparent at birth or shortly thereafter, whereas others present later in life. This chapter will focus on congenital lesions that can be recognized in the fetus or the newborn. Many congenital cervical lesions may be diagnosed prenatally, making it essential for pediatric radiologists to be familiar with their general patterns on…
Embryology of the Neck Accurate diagnosis and successful treatment of congenital anomalies and masses of the neck are dependent on an understanding of the complex embryologic development of this region and the anomalies that result from abnormal development. This chapter will focus on the embryology of the neck and the oral cavity. The embryology of the orbit, face and sinuses, temporal bone, and ear are addressed…
Overview Pediatric neoplasms of the temporal bone are relatively infrequent. However, the imaging specialist has to be familiar with the common malignancies and their imaging appearances. One important task of the radiologist is to define the extent of the lesion both within the temporal bone and, if present, intracranially ( Box 12.1 ). Box 12.1 The imaging report of a temporal mass should include: Location (external…
Infectious and inflammatory disorders commonly involving the temporal bone; external, middle, and inner ear; and the facial nerve are discussed in this chapter. The auricle, the cartilaginous canal, and the external auditory canal (EAC) comprise the external ear, with the tympanic membrane representing the division between the external and middle ear. The middle ear is predominately composed of the tympanic cavity and its contents. The Eustachian…
The discussion of congenital and neonatal temporal bone abnormalities in this chapter is approached from lateral to medial. External canal atresia and associated middle and inner ear anomalies are discussed initially. Isolated middle ear anomalies with associated branchial arch malformations are then addressed, along with associated anomalous development of the middle ear windows. A classification and description of inner ear malformations is discussed along with potential…