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Edward syndrome

Dr Abhilash Sandhyala and Dr Frank Gaillard et al.

The Edward syndrome (also known as trisomy 18) along with Down syndrome (T21) and Patau syndrome(T13), make up the only three trisomies to be compatible with extra-uterine life in non mosaic forms, albeit in the case of Edward's only for a week or so.

Epidemiology

After Down syndrome it is the second commonest autosomal trisomy and the overall incidence is estimated to be at ~ 1 : 3000 - 8000. There is an increase in incidence with increasing maternal age.

Syndromic spectrum

Trisomy 18 fetuses can have multiple anomalies in multiple systems. Over 130 ! features have been reported. Out of the three main trisomies, this trisomy has highest incidence of major structural anomalies.

Features include

congenital heart disease : 90 - 95%
central nervous system / spinal abnormalities : 70%
- choroid plexus cysts (especially if cysts are large and bilateral ⁶) : found in 25 - 43 % with trisomy 18
- agenesis of the corpus callosum : < 10%
- Dandy Walker continuum
- mega cisterna magna ⁶ :
- mental retardation
- neural tube defects : ~ 20% ⁷
  - myelomeningocoele / spina bifida :
IUGR : 60 - 90% (tends to occur from early in gestation)
facial / calvarial abnormalities
- micrognathia
- dolichocephaly : strawberry skull : as a result of frontal lobe hypoplasia.
- low set ears
- hypertelorism
- cleft lip + / - palate
cystic hygroma : ~ 20 %
skeletal abnormalities
- hand anomalies
  - clenched hands with overlap of 2^nd and 3^rd digits : 80%
  - radial ray anomalies
  - absent thumb
- feet anomalies
  - rockerbottom feet : typical feature
  - club feet
- prominent occiput
- short neck
umbilical cord
gastrointestinal - thoracic anomalies
- bowel containing omphalocoele : ~ 20 - 25%
- congenital diaphragmatic hernia : ~ 10%
renal anomalies
- antenatal hydronephrosis
- urethral duplication
- horseshoe kidney : 20% ³

Pathology

Markers

The following serological markers (often termed a triple screen) are generally lower than expected for that of pregnancy.

MSAFP : maternal serum alpha feto protein *
oestriol
beta human choriotrophic gonadotrophin (bHCG)

Prognosis

The syndrome carries an extremely poor prognosis with a mean infant survival of 48 days ⁴. The risk of recurrence for a future pregnancy is ~ 1 % greater than that adjusted for maternal age ⁷.

Differential diagnosis

pseudo-trisomy 18 - Pena-Shokeir syndrome : an autosomal recessive condition that can contain some overlap in the clinical features of that of trisomy 18

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