Craniosynostosis

Overview

The infant calvarium (skull) is made up of a series of bones that are connected by fiberous tissue which are called cranial sutures. These cranial sutures are the growth center of the infant calvarium.
craniosynostosis-1 craniosynostosis-2
Growth occurs perpendicular to these cranial sutures allowing for expansion of the calvarium. This growth is critical as the infant brain grows approximately 60% of adult size in the first year of life.

craniosynostosis-1

Craniosynostosis is the premature fusion of the cranial suture. The incidence of this cranial deformity is 1 in 2000 births. The result of this fusion is a focal point of growth restriction. This “sticky point” does not allow the infant calvarium to grow normally. As a result, there is compensatory growth parallel to the area of synostosis. This phenomina is important for several reasons. First there is potential for pressure on the growing brain and second the growing calvarium has an abnormal appearance.

craniosynostosis-4

Dependent on which cranial suture or sutures have fused the head shape takes on a predictable and recognizable pattern of head deformation.

SCAPHOCPHALY: SAGITTAL SUTURE
SCAPHO: BOAT

PLAGIOCEPHALY: UNILATERAL CORONAL
PLAGIO: OBLIQUE, TWISTED

TRIGONOCEPHALY: METOPIC SUTURE
TRIGONO: TRIANGULAR

BRACHYCEPHALY: BILATERAL CORONAL
BRACHY: FLAT

LAMBDOIDAL: POSTERIOR PLAGIOCEPHALY
MULTIPLE SUTURES: CLOVER LEAF DEFORMITY

Diagnosis and workup

Typical of craniosynostosis is an abnormal head shape at birth that worsens with time. This is different from deformation plagiocephally which typically improves with time. Early recognition of an abnormal head shape that does not fit the typical pattern of positional plagiocephaly is vital in minimizing long term issues as related to craniosynostosis.

If craniosynostosis is suspected the infant should be evaluated by a trained craniofacial surgeon. In addition to a comprehensive history and physical exam the surgeon may choose to obtain a CT scan which is an objective and definitive measure for the presence of craniosynostosis.

craniosynostosis-6

What are the risks of untreated craniosynostosis?

This topic is heavily debated. Intuitively it would make sense that if the infant skull is not expanding at the same rate at the growing brain there is the risk of pressure on the infant brain. This is referred to as increases in intracranial pressure. The risk of increases in intracranial pressure, as relates to craniosynostosis, is dependent on if one or more sutures are effected. If one sutures is involved the risk is approximately 20%.   This risk increases to nearly 50% if multiple sutures are involved. The reported risks are cognative delays, visual impairment and neuropsychiatric disorders. These risks have been reported to be significantly reduced if the offending sutures is removed and/or the calvarium is expanded. (1)

Timing of surgery and surgical options

The goal of surgery is to remove the fused cranial suture with or without cranial remodeling. The purpose of this is to allow for the brain to grow unrestricted and to reverse the cranio-orbital deformity. The type of reconstruction offered is dependent on the severity of the deformity, the type of synostosis and the age at presentation to the craniofacial surgeon.

Endoscopic minimally invasive strip craniectomy

This technique is actually an old technique revisited. This surgical option is very effective if the child is diagnosed and evaluated by a craniofacial surgeon prior to 3 months of life. With this technique the fused cranial suture is removed though a small incision(s). Following the procedure the child is placed in a custom cranial molding helmet. The purpose of the helmet is to mold the head into a more normal orientation over time.

The advantages of this technique are smaller scars, shorter hospital stay, potential for less blood loss, and less post-operative swelling. The disadvantage is that the deformity takes time to correct although if done early in life the long term results are comparable to more traditional techniques.

craniosynostosis-1 craniosynostosis-5

Endoscopic miminally invasive craniectomy for sagittal craniosynostosis

Traditional cranial vault remodeling

This operation is typically performed between 4 and 8 months of life. With this technique the fused suture is also removed. In addition, the deformity that is present at the time of surgery is correct such that at the completion of the procedure the infant will have a more normal head shape.

The major advantage of this technique is that the aberrant anatomy is normalized immediately following surgery, there is no need for a post-operative helmet, and it provides a better long term result if the infant is not treated prior to 3 months of age. The disadvantage is a larger scar in the hair bearing scalp, greater potential for blood loss and a somewhat longer hospital stay.

craniosynostosis-7

Traditional cranial vault remodeling for sagittal craniosynostosis

Summary

Craniosynostosis is the premature fusion of the growth center of the infant skull that results in predictable patterns of head deformity. Early recognition of abnormal and worsening head shape is essential and should be followed by evaluation and discussion with a trained craniofacial surgeon.

References

  1. Intracranial pressure in craniostenosis. – Renier D; Sainte-Rose C; Marchac D; Hirsch JF – J Neurosurg – 01-SEP-1982; 57(3): 3
  2. Congenital Synostoses Frank S. Ciminello MD, and S. Anthony Wolfe MD, FACS eMedicine,
  3. Craniofacial Distractor Applicator Dorfman DW, Ciminello FS, and Wong GB J Craniofacial Surg. 20(2) pgs 475-477, 2009