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BMJ No 7110 Volume 315 Editorial Saturday 20 September 1997
Occipital plagiocephaly: an epidemic of craniosynostosis?Craniosynostosis needs to be distinguished from more common postural asymmetry
One cause of plagiocephaly is craniosynostosis, which is premature
fusion of the cranial sutures-the adaptive fibrous joints between the
bones of the skull. The resulting abnormal skull shape is usually an
isolated anomaly but it may be associated with a craniofacial syndrome
such as that of Crouzon or Apert. The skull shape is predictable from
the suture or sutures involved. Premature fusion of the lambdoid
sutures, which separate the occipital from the parietal bones
bilaterally, may cause occipital plagiocephaly.
Premature lambdoidal fusion is nevertheless rare.(2, 3) The
apparently increasing incidence of babies presenting with occipital
flattening, either unilaterally or bilaterally, has coincided with
current advice to nurse infants in a supine position to combat cot
death.(4) This phenomenon represents postural, or
deformational, plagiocephaly, resulting from unrelieved pressure on the
occiput. Asymmetrical influences on the skull base caused by
torticollis or cervical spine anomaly may have a similar effect.
In reviewing 75 children presenting consecutively with occipital
plagiocephaly to the supraregional craniofacial centre at Great Ormond
Street Hospital for Children we have identified some characteristic
features of the course of this "epidemic." Two thirds of the
infants and children were boys; two thirds presented with a right sided
unilateral flattening; and in two thirds this asymmetry had started
some time after birth, progressed until around the age of 6 months, and
remained stable thereafter. Half the group showed asymmetry of head
turning. The delayed presentation and consistent history of
asymmetrical head turning is not characteristic of lambdoid
synostosis, in which the head shape is abnormal from birth.
Postural plagiocephaly, related to the deformational asymmetry of
head turning, is a far more likely cause.
Postural plagiocephaly and true lambdoidal synostosis can be
distinguished by clinical examination and confirmed by routine
radiological investigation.(2) Lambdoid synostosis produces
a unilateral occipitoparietal flattening when viewed from behind. The
territory of the lambdoid suture presents as a palpable bony ridge,
with a bony prominence at the skull base behind the ear on that side,
which is displaced inferiorly and posteriorly. The skull base thus
seems to tilt to the affected side, giving the head a parallogram shape
when viewed from behind. Although the postural group also displays
unilateral occipitoparietal flattening, there is no palpable bony ridge
of sutural fusion and no bony prominence at the skull base behind the
ears, which are level. The ear on the flat side is displaced anteriorly
rather than posteriorly and often folded forward. The skull base has no
tilt, and therefore the head does not appear as a parallelogram from
behind. True lambdoid synostosis is readily distinguishable
radiologically, appearing sclerotic on plain radiography and
obliterated by bone on computed tomography. The suture remains
radiologically open in the postural group.
Why is it important to distinguish the synostotic from the
deformational? Clearly the course of the two conditions is different,
and this directly affects clinical management. True synostosis is
likely to have been present from birth, is progressive, and is unlikely
to improve spontaneously. It confers the risk that intracranial
pressure may be raised, although this occurs in less than 10% of cases
when only a single suture is implicated.(5) Postural
plagiocephaly, however, confers no risk of intracranial pressure
disturbance, and in over 70% of our series the skull shape improved
spontaneously. As the child matures and head control improves, the
plasticity of the skull base initially allows the deformity to
stabilise and then gradually improve. As scalp hair grows the cosmetic
deformity becomes less noticeable. The spontaneous improvement may be
encouraged by regular changes in sleeping position, perhaps helped by
orthotics.(6) In severe cases surgical correction may be
proposed, but parents should be aware that this would be a cosmetic
procedure and not without risk in view of the proximity of the
posterior dural venous sinuses.
Thus in most children presenting with an occipital plagiocephaly
there will be no craniosynostosis, and even when there is, functional
impairment is unlikely. Distinguishing between craniosynostotic and
positional Barry M Jones
Richard Hayward
Robert Evans
Jonathan Britto
Craniofacial Centre,
References
1 Ortega R. Unkind cut.Wall Street Journal
1996; 29 Feb: A1-5.
2 Huang MH, Gruss JS, Clarren SK, Mouradian WE, Cunningham ML,
Roberts TS, et al. The differential diagnosis of posterior
plagiocephaly: true lambdoid synostosis versus postitional moulding.
Plast Reconstr Surg 1996;98:765-4.
3 Pople IK, Sanford RA, Muhlbauer MS. Clinical presentation and
management of 100 infants with occipital plagiocephaly. Pediatr
Neurosurg 1996;25:1-6.
4 American Academy of Paediatrics Task Force on Infant Position
and SIDS. Positioning and SIDS. Pediatrics 1992;89:1112.
5 Gault D, Renier D, Marchac D, Jones BM. Intracranial pressure
and intracranial volume in children with craniosynostosis. Plast
Reconstr Surg 1991;90:377-81.
6 Ripley CE, Pomatto J, Beals SP, Joganic EF, Manwaring KH, Moss
SD. Treatment of positional plagiocephaly with dynamic orthotic
cranioplasty. J Craniofac Surg 1994;5:150-9.
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