ANTENATAL DIAGNOSIS OF FETAL HEMIVERTEBRAE

Abstract

Introduction: Although the ultrasound diagnosis of neural tube defects has been described extensively, anomalies of the fetal vertebral bodies have received little attention. This study aims to document the incidence of congenital hemivertebrae, the association with defects of other organ systems and discuss the outcome.

Methods: All fetuses with ultrasonographically detected vertebral anomalies presenting to the above institution over a four year period were included in the study. Those with open neural tube defects were excluded. The level and Cobb angle (where possible) were estimated from the 18 week scan. Associated congenital anomalies were noted. Radiographs were taken soon after birth and checked for accuracy of original diagnosis and patients were monitored for curve progression.

Results: Fourteen fetuses with congenital hemivertebrae were found from a total of 12,000 routine antenatal scans. Maternal age ranged from 22–32 years (mean 26.8 years) with an average term of 36.3 weeks (range 29–40). Only two fetuses were born prematurely: one at 33 weeks as part of a twin gestation (only one of the twins had an isolated hemivertebrae) and the other at 29 weeks via emergency caesarian section for fetal distress. This pregnancy was complicated by the oligohydramnios sequence (Potter syndrome). Ten of 14 fetuses had an isolated hemivertebrae. Two had VATER association (oesophageal and anal atresia) and two had multiple mosaic type congenital scoliosis, one of which had associated rib and abdominal wall malformation. All pregnancies resulted in live births. All except one child remain well at latest follow-up (average 25 months). The infant born at 29 weeks has had multiple complications of prematurity. Vertebral anomalies appeared in the thoracic spine in five, the lumbar spine in eight and the sacrum in one resulting in scoliosis in 13 and kyphosis in one. The average antenatal Cobb angle was 30°. The average postnatal Cobb angle was 32° (range 18–42). Accuracy of localisation (level and type) was good with only one error due to inability to see the S1 hemivertebrae. Six of the 14 had surgery before the age of 24 months, with the youngest aged three months. In this group the average pre-operative Cobb angle was 35° (range 25–42°). Three patients had anterior and posterior fusion in-situ without instrumentation. Three patients had hemivertebrectomy with correction and posterior instrumentation of the spine.

Conclusion: In general sonographically detected isolated fetal hemivertebrae carry a good prognosis. If associated with the oligohydramnios syndrome the fetus is at high risk. Ultrasound appears accurate in the diagnosis of both the level and type of congenital malformation. The value of early surgical management needs continued assessment.