Diagnostic ultrasound ( PDFDrive )

1532 PART V Pediatric Sonography
A
B
C
D
FIG. 45.24 “Sunburst” or Radial Arrangement of Sulci in Agenesis of the Corpus Callosum. (A) and (B) Midsagittal sonograms. (C)
Midsagittal magnetic resonance image. (D) Sagittal pathologic specimen. Arrows indicate radial array of sulci. (C with permission from Osborn AG.
Diagnostic neuroradiology. St Louis: Mosby; 1994 234 ; D with permission from Friede R. Developmental neuropathology. 2nd ed. New York: Springer-
Verlag; 1975. 42 )
Complete agenesis of the cerebellar vermis without
hydrocephalus occurs in Joubert syndrome, with associated
symptoms including episodic hyperpnea, ataxia, abnormal eye
movements, and mental retardation. 31 his anomaly is thought
to be caused by the inability of the posterior fossa axons to
cross the midline. here is a Meckel-like syndrome with Dandy-
Walker malformation, polycystic kidneys, hepatic ibrosis, and
hand and genital anomalies. True Meckel-Gruber syndrome
includes an encephalocele, renal cystic dysplasia, short limbs, and
polydactyly. 60
DISORDERS OF DIVERTICULATION
AND CLEAVAGE:
HOLOPROSENCEPHALY
Holoprosencephaly results from a failure of diverticulation when
the primitive prosencephalon does not divide into the
telencephalon and the diencephalon between the fourth and
eighth weeks of gestation. he telencephalon normally develops
into the cerebral hemispheres, ventricles, putamen, and caudate
nuclei. he diencephalon becomes the third ventricle, thalami,
hypothalamus, and lateral globus pallidus. Holoprosencephaly
represents a spectrum of malformations that form a continuum
from most severe, with no separation of the telencephalon into
hemispheres (alobar holoprosencephaly), to least severe, with
partial separation of the dorsal aspects of the brain (lobar
holoprosencephaly). he septum pellucidum is absent in all forms
of holoprosencephaly (Fig. 45.28).
Septo-Optic Dysplasia
Some consider the mildest form of lobar holoprosencephaly to
be septo-optic dysplasia, with absence of the septum pellucidum
and optic nerve hypoplasia (Fig. 45.29, Video 45.8). About twothirds
of these infants have hypothalamic-pituitary dysfunction.
hey may have visual symptoms and growth restriction. In