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Definition/Background
The Chiari II malformation is a complex anomaly with skull,
dural, brain, spine, and spinal cord manifestations. This disorder is almost
invariably associated with myelomeningocele.
Characteristic
Clinical Features
Two distinct age-dependent syndromes are identified in Chiari II malformations. One syndrome
involves infants, and the other involves older children. Signs and symptoms
during infancy include respiratory distress, difficulty swallowing, inspiratory
stridor, apnea, weakness or spasticity of the upper or lower extremities, and scoliosis.
Signs and symptoms during childhood include syncopal episodes, spastic
quadriparesis, nystagmus, weakness in upper extremities with increased tone,
and exaggerated deep-tendon reflexes.
Characteristic
Radiologic Findings
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CT and MR can both evaluate for Chiari II malformation. The
bony changes can be much better appreciated on CT scans.
Bony changes:
Small posterior fossa, concave clivus, and
petrous ridges, gaping foramen magnum, calvarial defects (Lacunar skull).
Dural changes:
Fenestrated falx.
Brain: Inferiorly
displaced, peg-shaped tonsils, towering cerebellum, cerebellum creeping around
the brain stem, beaked tectum, interdigitating gyri.
Ventricles:
Hydrocephalus, colpocephaly, and elongated and inferiorly displaced fourth
ventricle.
Spine and spinal
cord: Spina bifida, segmentation anomalies, diastomatomyelia, and
myelomeningocele.
Less Common
Radiologic Manifestations
Corpus callosal agenesis, heterotopia, and poly- microgyria.
The patient is an 8-year-old girl with spastic quadri-
paresis and exaggerated deep-tendon reflexes.
Sagittal T1WI demonstrates a relatively small posterior fossa with inferiorly displaced peg-shaped cerebellar tonsils. Also noted is concave clivus (arrow).
Axial T2WI demonstrates beaked tectum. Also noted is cerebellum creeping around the brain stem.
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Labels: Brain, Congenital Anomalies
