B. Developmental disorders of the spinal cord
- 1. Syringomyelia
- a. commonly occurs at cervical levels; clefts may extend into the brainstem
- b. can be caused by a variety of etiologies besides defective development
including hemorrhage; associated with Chiari I defect
- c. clinically, the patient often presents with loss of pain and
temperature symmetrically in the hands as well as wasting of the hand
muscles. This is due to encroachment of the cystic cavity in the cord on
the anterior commissure which carries pain fibers and the anterior horns
which contain the motor neurons which innervate the hand.
C. Developmental disorders of the brainstem
- 1. Agenesis
- a. inferior olivary nuclei may be absent for no known reason
- b. pyramids may be absent and this anomaly is often related
to abnormalities of the cerebral hemispheres
D. Developmental disorders of the cerebellum
- 1. The Arnold-Chiari malformation includes displacement of the
cerebellum into the cervical segments. See section III.
- 2. The Dandy-Walker malformation includes lateral displacement
of cerebellar hemispheres by a dilated 4th ventricle. See section III.
- 3. Agenesis of the various functional parts of the cerebellum,
alone or in combination, may occur.