Radiological Diagnosis

Apert Syndrome

Radiological Findings

Lateral skull radiograph shows craniostenosis in the form of tower like skull with decreased anteroposterior and increased vertical skull length with convolution markings suggesting turribrachycephaly with raised intracranial tension. Also seen are shallow orbits and hypoplastic maxillae [Figure - 1]. Radiograph of both hands shows bilateral cutaneous syndactyly of first four fingers sparing the little finger. There is synostosis of proximal end of fourth and fifth metacarpals and of second, third and fourth phalanges, with radial deviation of phalanges, which is bilaterally symmetrical. There is delta shaped proximal phalanx of thumbs in both hands [Figure - 2]. Radiograph of both feet shows cutaneous syndactyly of all toes called Sock Feet appearance. There is delta shaped deformity of proximal phalanx of both great toes with absent distal phalanx [Figure - 3]. 3D CT Reconstruction of skull shows tower like skull vault with depressed nasal bridge and proptosis of eyeballs [Figure - 4]. CT and MRI of brain (not shown here) showed aqueductal stenosis with hydrocephalus of lateral and third ventricles.

Discussion

Apert syndrome was first described by Eugene Apert in 1906 as a triad of craniosynostosis, syndactyly and maxillary hypoplasia. It is a rare autosomal dominant disorder and most common of different types of acrocephalysyndactyly [1],[3]. Prevalence is estimated at 1 in 65,000 live births. Apert syndrome accounts for 4.5% of all cases of craniostenosis. Asians have the highest prevalence of 22.3 per million live births [2].

There is growth inhibition in the sphenofrontal and coronal suture area beginning very early in fetal life. During early infancy, the coronal suture area is closed prematurely. Compensatory growth occurs at the remaining open sutures to allow continued brain growth; however, complex, multiple sutural synostoses frequently extends to premature fusion of the sutures at the base of the skull, causing midfacial hypoplasia, shallow orbits, a foreshortened nasal dorsum, maxillary hypoplasia and occasional upper airway obstruction [4],[5]. Patient may present with symptoms of headache and vomiting due to acute increased intracranial pressure, especially in cases of multiple suture involvement and with stridor and sleep apnea due to upper airway obstruction resulting from craniosynostosis of sutures of skull base. Many patients exhibit mental retardation, though there may be patients with normal intelligence [6]. Patients have apparent low-set ears with occasional conductive hearing loss. Eyes exhibit down-slanting palpebral fissures, shallow orbits and proptosis. Nasal bridge is markedly depressed. Other features are prognathism, high arched palate and cleft palate.

Syndactyly involves the hands and feet with partial-to-complete fusion of the digits, often involving second, third and fourth digits. In severe cases, all digits are fused (Mitten Hands and Sock Feet), with the palm deeply concave and cup-shaped and the sole supinated. Hitchhiker posture or radial deviation of short or broad thumbs results from abnormal proximal phalanx [3]. Brachydactyly and synonychia may occur. Common CNS malformations include agenesis of the corpus callosum, malformed limbic structures, variable ventriculomegaly, encephalocele, gyral abnormalities, hypoplastic cerebral white matter and heterotopic gray matter. Progressive hydrocephalus is uncommon. Papilloedema and optic atrophy with loss of vision may occur with subtle increased intracranial pressure. Congenital cervical spinal fusion may occur especially of C5-C6 vertebrae. Skin lesions are frequent after adolescence. There may be associated cardiovascular, gastrointestinal or genitourinary anomalies, which occur in less than 10 percent of cases. Recurrence risk for an affected individual to have an affected offspring is 50%. Prenatal ultrasonographic diagnosis can be made based on findings of acrocephaly, mitten like hands and proximally placed and radially deviated thumbs [7].