Cephalocele refers to the outward herniation of CNS contents through a defect in the cranium. The vast majority are midline.
The estimated incidence is 0.8-4:10,000 live births with a well recognized geographical variation between types; however, this has been speculated to be underestimated as many may result in elective termination, in utero demise, or stillbirth. There may be a female predilection .
The presentation may vary widely depending upon the type of defect.
- large mass seen extending from cranium on prenatal ultrasound
- small cranial soft tissue mass palpated in childhood (e.g. atretic cephalocele)
- in utero demise (severe defect)
It is thought to arise due to failed closure of the rostral end of the neuropore. This may result from either overgrowth of neural tissue in the line of closure, or failure of induction by adjacent mesodermal tissues which interferes with normal skull closure.
Cephaloceles can be classified into 5 types, based upon the herniated contents :
- meningocele: CSF lined by meninges
- gliocele: CSF lined by glial tissue
- meningoencephalocele: CSF, brain, and meninges
- meningoencephalocystocele: CSF, brain, meninges, and part of a ventricle and choroid plexus
- atretic cephalocele: dura, fibrous tissue, and degenerated brain
- occipital cephalocele: most common, up to 75%
- parietal cephalocele: up to 37%
- frontal cephalocele/fronto-ethmoidal cephalocele: ~10%, this type is most common in Asia
- petrous apex cephalocele : rare
- intra sphenoidal cephalocele : rare
Additional congenital anomalies may be present in up to 50 % of cases. They include
- non-aneuploidic syndromic
- non-syndromic CNS anomalies
- non-syndromic non-CNS anomalies
- maternal serum alpha-fetoprotein (MSAFP) may be elevated
Sonographically, these lesions may appear as:
- a cyst protruding from the fetal calvarium representing a meningocele or cyst within cyst appearance
- a solid mass protruding from the calvarium representing a herniated brain: encephalocele
- either or both of the above associated with a defect in the calvarium
Treatment and prognosis
The overall prognosis is variable dependent on severity and other associations (presence of hydrocephalus, microcephaly, etc). If a large cephalocele is noted in an antenatal ultrasound scan, it generally implies a poor prognosis.
- Spina bifida
- fetal hydrocephalus
- Dandy-Walker continuum
- Trisomie 18
- Frontonasale Dysplasie
- dysgenesis of corpus callosum