Chapter 68. Congenital Malformations of The Skeletal System - Review of Medical Embryology Book

SPINA BIFIDA OCCULTA results from failure of fusion of the halves of the vertebral arch, most often in the lumber and sacral regions

It is a common defect but usually of no significance
The skin over the bifid spine is usually intact, and there may be no visible signs of the defect except for a "dimple" or tuft of hair
Severe types do exist and are described under Nervous system development

KLIPPEL-FElL SYNDROME (brevicollis): very rare; extreme shortening of the neck due to a reduced number of cervical vertebrae. The rest of the cervical vertebrae are usually abnormal in shape and may be fused. Associated with other abnormalities
ASYMMETRICALLY FUSED VERTEBRAE or parts of vertebrae missing; an increase or decrease in vertebral number is not uncommon due to the complicated process of formation and rearrangement of the segmental sclerotomes in development

IF PART OR ALL OF A VERTEBRA is missing, the corresponding ribs are generally gone
IN SEVERE CONGENITAL SCOLIOSIS, the ribs on the concave side of the chest are often fused or branched
ACCESSORY RIBS: usually the cervical rib (lumbar ribs are less common)

Attached to the seventh cervical vertebra; may be unilateral or bilateral
Pressure effects on the brachial plexus or subclavian vessels may produce symptoms
From retention and development of costal processes of cervical or lumbar vertebrae

FUSED RIBS: this may occur posteriorly when 2 or more ribs arise from a single vertebra

Skull malformations range from major defects incompatible with life to those that are minor and relatively unimportant. The abnormalities are manifold, and either all or part of the skull may be involved. They are frequently associated with brain defects

CRANIOSCHISIS OR ACRANIA: the cranial vault is almost absent and a large spinal defect is often present. Also associated with anencephaly

Due to a failure of the cranial end of the neural tube to close during week 4, thus the cranial vault does not form

If sagittal suture: a long, narrow, wedge-shaped skull (scaphocephaly)
If the coronal suture: a high, towerlike skull (oxycephaly or acrocephaly)
If coronal or lambdoid suture closes on one side: twisted and asymmetric skull (plagiocephaly)

MICROCEPHALY: cranium is normal size or slightly small, but there is no abnormal closure of the sutures. It is primarily an abnormality of the CNS in which the brain and skull both fail to grow