Diagnostic ultrasound ( PDFDrive )

CHAPTER 45 Neonatal and Infant Brain Imaging 1525
Congenital Brain Malformations
Neural tube
closure
Anterior and posterior
neuropore closure
Segmentation
Diverticulation
DISORDERS OF ORGANOGENESIS
Disorders of Neural Tube Closure
Chiari malformation
Agenesis of the corpus callosum
Lipoma of the corpus callosum
Dandy-Walker malformation or variant
Posterior fossa arachnoid cyst
Teratoma
Disorders of Diverticulation and Cleavage
Septo-optic dysplasia
Holoprosencephaly (alobar, semilobar, lobar)
Disorders of Sulcation/Cellular Migration
Lissencephaly
Schizencephaly
Heterotopias
Pachymicrogyria or polymicrogyria
DISORDERS OF SIZE
DISORDERS OF MYELINATION
DESTRUCTIVE LESIONS
DISORDERS OF HISTOGENESIS
Neurocutaneous Syndromes (Phakomatoses)
Tuberous sclerosis
Neuroibromatosis
Congenital Vascular Malformations
DISORDERS OF CYTOGENESIS
Congenital neoplasms
Modiied from DeMeyer classiication of anomalies. 21,22,48
Stages of Brain Development a
FIG. 45.18 Stages of Organogenesis. The neural tube closure at
3 to 4 weeks’ gestation, including closure of the anterior and posterior
neuropores. At 5 to 6 weeks, the brain segments and ive types of
diverticula form. First, the paired olfactory tracts, optic tracts, and cerebral
ventricles develop, then the unpaired pineal and pituitary. Neural proliferation,
migration, organization, and myelination occur after these stages.
(With permission from DeMyer W. Classiication of cerebral malformations.
Birth Defects Orig Artic Ser. 1971;7[1]:78-93. 48 )
a growing brain with the necessary building blocks to form
properly. Finally, millions of cells must migrate into the organized
functional structure that is recognized as a normal brain. he
germinal matrix is a source of many of the migrating cells and
eventually disappears as they migrate out. Myelination occurs
from the second trimester to adulthood but is most active from
directly ater birth until 2 years of age. 46,47 Migration and myelination
defects are best evaluated with MRI and have been well
described by Barkovich. 31 MRI has greatly increased our understanding
of brain development, and many genetic and environmental
factors may interfere with normal development.
Destructive lesions can occur at any point in brain development.
Congenital malformations of the brain are oten diagnosed
Cytogenesis: development of molecules into cells
Histogenesis: development of cells into tissues
Organogenesis: development of tissues into organs
Neural tube closure (dorsal induction: 3-4 weeks’
gestation)
Diverticulation (ventral induction: 5-6 weeks’ gestation)
Neuronal proliferation (8-16 weeks’ gestation)
Neuronal migration (24 weeks’ gestation to years)
Organization (6 months’ gestation to years after birth)
Myelination (birth to years after birth)
a Stages overlap in time but may be individually abnormal.
Modiied from Volpe JJ. Brain injury in premature infants: a complex
amalgam of destructive and developmental disturbances. Lancet
Neurol. 2009;8(1):110-124. 46
in utero, and neonatal sonographic imaging may be needed to
conirm or further evaluate the prenatal diagnosis. In most cases,
MRI may be required to clarify the ultrasound indings. In general,
MRI is preferred over CT because it best demonstrates sulcal
patterns, migrational anomalies, and abnormal myelination.
Disorders of cerebellar growth and development are now better