Abnormal Skull Shape

Abnormal skull shape generally occurs because the bones of the skull have grown together (suture fusion or synostosis) or because the bones of the skull have been moved to an incorrect place but are not fused (deformational ). Most abnormal skull shapes come from the birth process and subsequent flattening of one side of the head. It may also be related to a tightened neck muscle on one side (torticollis), abnormal neck spine (fusion) or abnormal eye muscles.

 

Craniosynostosis (fusion of the skull bones)

The skull is formed by five bones, with gaps between the bones (sutures). These six gaps are important to allow the bones to move during the birth process. They also allow the brain and skull to increase in size as the baby grows. If one or more of these "sutures" grow together, then the rest of the skull has to grow in a different direction, causing the skull shape to be abnormal. This problem can only be corrected surgically by a team of pediatric neurosurgeon and pediatric/craniofacial plastic surgeon. Most surgeries are completed before one year of age; some are completed at three to four months of age. The two problems that need to be corrected include increasing the volume of the skull to prevent increased pressures on the brain within the skull (intracranial pressure) and improving the appearance of the skull and forehead. Below is a list of terms that may be used to describe the exact suture or sutures involved.

Plagiocephaly - literally means "crooked skull" and can be used to describe a deformational skull shape or synostosis of the unicoronal suture (left or right). It is important to differentiate between the two causes. The asymmetry is usually on one side of the head and may involve the bones around the eye. Occasionally, the posterior suture (lambdoid suture) will fuse and cause a plagiocephaly.

Brachycephaly - usually refers to bicoronal synostosis (both coronal sutures involved) and causes the forehead region to be wide and high. The eyes may appear wide apart.

Trigonocephaly - refers to fusion of the metopic suture causing a triangular shaped forehead. The eyes may be close together. Some babies will have a ridge over the midline suture but a mild deformity of the forehead.

Patient with
Metopic Synostosis and trigonocephaly

A: Preop

B: 2 years after
     frontal orbital
     advancement

 
A                           B
 
Scaphocephaly - The most common suture to fuse is the middle or sagittal suture. Often the back or front of the skull will be worse but the overall shape is a long skull with a shortened distance from ear to ear.
Pre-op
CAT scan
Diagram of surgery
2 years post-op
Patient with sagital synostosis and scaphocephaly
Multiple suture fusion - Occasionally more than one suture will be fused. The resulting head shape is dictated by the number and location of the suture. These cases usually require earlier intervention and careful monitoring of intracranial pressures on the brain.

 

Suture fusion associated with other congenital defects

Most babies with fusion of the skull suture will not have any other anomalies. Rarely, the suture fusion is related to a syndrome meaning a collection of other congenital anomalies, not directly related to the skull. Some of the syndromes have associated genetic mutations and may be hereditary while others are merely clinical diagnoses. The following are a few of the more common syndromes associated with
craniosynostosis:
  • Apert syndrome - may have fusion of skull sutures, fusion of several fingers of the hands and feet, and small face with prominent eyes (midface hypoplasia and proptosis). Babies often have a very large soft spot on the forehead.

  • Crouzon syndrome - May be similar to Apert's in skull shape. Often has more prominent eyes and small midface and no hand or foot involvement. The soft spot is usually small or gone completely.

  • Pfeiffer syndrome - Similar to Crouzon syndrome but with broad thumbs and great toes.

  • Saethre-Chotzen syndrome - may or may not have fusion of the cranial sutures. Upper lid droop and webbing of index and long fingers and fourth and fifth toes are common. External ear anomalies may also be present. Genetic testing is now available to confirm the diagnosis in most cases.

Positional head deformities (no suture fusion)

Positional head deformities are quite common and in some reports have been found in 40-90% of newborn infants. The initial cause may be related to the birthing process (passage through the birth canal). Another cause of positional head deformities may be a persistent tilt of the baby's head to one side (torticollis). Again the most common cause may be related to the position of the baby in the uterus and the neck muscles will stretch with time and specific neck exercises. Occasionally, the muscle will have tight scar that will not stretch and the muscle should be divided to correct the head position. This can be done with small incisions that are well hidden and a camera (endoscopic surgery).
 
Rarer causes of torticollis include abnormal eye muscles which cause the head to tilt to improve vision, and abnormalities of the neck spine. Because the brain grows very fast in the first three years of life and because no bones have grown together, the majority of the abnormal skull shapes will become normal with time. A certain percentage of patients will not improve and will require closer monitoring. Sometimes supporting the head on the flat side with pillows (so the baby is resting on the "non-flat" side)or moving the crib to a different position in the room may help. If the deformity persists, "helmet therapy" or "head banding therapy" may be used. The head device directs the growth of the skull through gentle persistent pressure. Careful and frequent monitoring is required. The benefits of this therapy are usually best between 4 and 15 months of age. This therapy has proven to be quite effective. In a few patients, helmet therapy does not work and surgical correction of the deformity is required.

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