Rachischisis

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Rachischisis

Last updated on Tuesday, September 9 2008 by jdmiles

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Anencephaly, sagittal section through cranium.
Anencephaly occurs secondary to failure of closure of the anterior neuropore. Exencephaly occurs initially, followed by destruction of the primitive brain secondary to unprotected exposure to amniotic fluid and intrauterine trauma.

Anencephaly, dorsal view of cranium
Destruction of the primitive cerebrum with replacement by granulation tissue results in a gelatinous mass referred to as the area cerebrovasculosa.

Chiari II malformation, dorsal surface of cerebellum
Compression of the inferior cerebellum secondary to its development within the foramen magnum.

Chiari II malformation, spinal cord and posterior fossa structures
Caudal displacement of dorsal posterior fossa structures results in kinking of the cervical spinal cord.

Chiari II malformation, complete dorsal view of dissected spinal cord and posterior fossa
The Chiari II malformation comprises meningomyelocele with abnormal hindbrain development.

Chiari II malformation, mid sagittal section through cerebellum and brainstem
Caudal displacement of dorsal posterior fossa structures results in herniation of the cerebellar tonsils into and through the foramen magnum.

Chiari II malformation, ventral surface of posterior fossa structures
In the Chiari II malformation, the cerebellum appears to wrap anteriorly around the brainstem, as pictured here.

Craniorachiscisis totalis, dorsal view of fetus
Craniorachiscisis totalis occurs due to complete failure of dorsal induction.

Craniorachiscisis totalis, fetal x-ray
Craniorachiscisis totalis demonstrates complete failure of dorsal fusion of bony structures.

Occipital encephalocele, ventral surface of brain
Encephalocele involving the occipital lobe is the most common form of encephalocele in the Western Hemisphere

Inienecephaly, dorsal view of fetus
Inienecephaly is a form of anencephaly occurring in combination with cervical rachischisis and retroflexion.

Luckenschadel, inner surface of skull
Luckenschadel, or multiple cranial lacunae, occurs with developmental anomalies producing uneven pressure on the membranous bones the skull during development. Classically, luckenschadel is seen in association with open neural tube defects such as the Chiari II malformation.

Meningomyelocele, dorsal surface of lower back
The abnormal neuroectodermal tissue comprising the meningomyelocele placode has been dissected to demonstrate continuity with the underlying spinal cord.