7.3 Pathologies

• Sacro-coccygeal teratoma
• Chordoma
• Caudal dysplasia
• Abnormalities in the closure of the neural tube
  • Spina bifida occulta
  • Spina bifida in combination with a dermoid cyst
  • Spina bifida aperta (meningocele, meningomyelocele, myeloschisis)
  • Anencephaly

Spina bifida aperta

In cases of spina bifida aperta, besides fissures of the osseous structures, one also finds abnormalities of the meninges and/or of the spinal cord itself.
The membranous covering can be present or absent. The mildest form is the meningocele where merely the meninges protrude under the skin through the cleft in the malformed vertebral arch.

Fig. 30; Fig. 30a
Schematic drawing of a meningocele. The spinal cord is in its normal location. Only a sack filled with cerebrospinal fluid, bounded by the dura mater, protrudes from below the skin.

In a myelomeningocele the meninges as well as the spinal cord (myelon) are found outside of the vertebral arch. They are visible as a protrusion under the skin; sometimes the skin can also be absent or only very thin.
In addition, the central canal is bloated and forms a cyst. In this case one speaks of a myelocystomeningocele.

Fig. 31; Fig. 31a
Schematic drawing of a myelo-
meningocele.
The spinal cord comes to the surface through the osseous defect and is normally covered only by a thin skin.

The myeloschisis (rachischisis) is the severest form of the spina bifida aperta. The nerve tissue is here fully bare and a dermal or meningeal covering is absent. With this abnormality, the closure of the neural folds fails to occur.

Abb. 32; Abb. 32a
Schematic diagram of a myeloschisis.
The nerve tissue lies open at the surface without a dermal covering.
This leads to the severest disorder of the innervation.

Anencephaly

Anencephaly represents a special kind of spina bifida. It arises when the neural folds do not fuse in the cranial region of the neural tube. When the fusion fails for the entire neural tube, one speaks of craniorachischisis totalis. Both anomalies are always fatal.