Isolated Plagiocephaly

Isolated synostotic plagiocephaly (SP) is a form of nonsyndromic craniosynostosis characterized by premature fusion of one coronal suture leading to skull deformity and facial asymmetry.

Epidemiology

Incidence is estimated at around 1 in 10,000 births.

Clinical description

Isolated SP is characterized by a rounded ipsilateral palpebral fissure, an ipsilaterally displaced nasal root, contralateral frontal bossing and skull asymmetry as a result of unilateral coronal synostosis. Mild facial hypoplasia and macrocephaly have been observed in some cases. Unilateral or bilateral hearing loss, and developmental delay or learning problems have also been reported in some patients. Frequent visual field abnormalities and defective eye movements were recently reported in 50% of infants with SP.

Etiology

A recurrent P250R mutation in fibroblast growth factor receptor 3 (encoded by the FGFR3 gene; 4p16.3) was found to be responsible for the majority of these familial cases and for some of the sporadic cases. Intrafamilial variability of the phenotype caused by the P250R mutation may result in patients presenting either plagiocephaly or brachycephaly within the same family. However, FGFR3 mutations have only been identified in a limited number of patients (7-10%); in most cases the etiology is unknown and is likely not to be genetically determined. Intrauterine deformational forces have been implicated but additional determinants such as maternal hematologic or metabolic disorders might be involved.

Diagnostic methods

Diagnosis is based on clinical examination and radiological evaluation by X-rays and 3D CT and/or MRI of the skull. Molecular screening for the FGFR3 mutation should be recommended as this mutation may be associated with additional anomalies (mild brachydactyly and fusion of carpal or tarsal bones) that are only detectable by radiographic analyses of the limbs.

Differential diagnosis

SP should be clearly distinguished from deformational plagiocephaly, a common form of plagiocephaly attributed to the supine sleep position that does not involve the sutures and does not usually require surgical treatment. The differential diagnosis should also include syndromes associated with premature fusion of one coronal suture (Crouzon, Pfeiffer and Saethre-Chotzen syndromes; see these terms), a distinction that mostly relies on the presence of limb anomalies in syndromic forms. Identification of the P250R mutation can be helpful for the differential diagnosis of synostotic plagiocephaly.

Genetic counseling

Most cases of SP are sporadic, but familial forms (2-3% of all cases) with autosomal dominant transmission have been reported.

Management and treatment

Surgical correction involving a bifrontal craniotomy is the most appropriate treatment for isolated SP. Hearing loss and visual defects need to be properly assessed before and after surgery.

Prognosis

Cranial expansion surgery at early stages during infancy usually results in normal intelligence in children and adolescents. However, the impact of reconstructive surgery on visual function has not yet been assessed.