Antenatal Diagnosis and Ultimate Outcome of Fetal Hemivertebrae

Spinal Unit, University Hospital
Queen's Medical Centre, Nottingham, UK

PURPOSE:
The ultrasound (US) diagnosis of neural tube defects has been well described. Anomalies of fetal vertebral bodies however have received little attention. This study documents the incidence of congenital hemivertebrae identified on routine antenatal US examination, the association with defects of other organ systems. The ultimate post-natal surgical outcome is discussed.

METHODS:
All fetuses with vertebral anomalies detected on US scan over a four-year period were included. Those with open neural tube defects were excluded. The level of anomaly and Cobb angle were measured on the 20 week scan and 4 weekly thereafter. Associated congenital anomalies were noted. Radiographs were taken 6 weeks after birth and correlated with the US for accuracy of original diagnosis. Post-natal outcome was determined.

RESULTS:
Fifteen fetuses with congenital hemivertebrae were identified from a total of 12,000 routine antenatal scans (incidence 0.125%). The average maternal age was 27 years (range 22-33). One fetus miscarried at 23 weeks. There were no terminations of pregnancy. All other pregnancies resulted in live births with an average term of 36.3 weeks (range 29-40). Two fetuses were born prematurely (one at 29 weeks and one at 33 weeks). Two of the fetuses were noted to have renal agenesis (one miscarriage, one live birth), one had VATER association and one had associated rib and abdominal wall malformation. In all ten fetuses had an isolated hemivertebrae and five had mixed anomalies. Vertebral anomalies appeared in the thoracic spine in six, the lumbar spine in eight and the sacrum in one, resulting in scoliosis in 14 and kyphosis in one. The mean antenatal Cobb angle was 30 degrees. There was no documented in-utero curve progression. The mean postnatal Cobb angle was 32 degrees (range 18 to 42). Accuracy of localisation (level and type) was good with only one error. The mean post-natal follow-up was 26 months (range 6 to 54). Six of the fifteen underwent surgery at a mean age of 12.4 months (range 1.5 to 35). Surgery included anterior and posterior convex hemi-epiphyseodesis in two and hemivertebra excision with fusion in situ in four. The mean pre-operative Cobb angle was 36 degrees (range 25-42) reducing to a mean of 26 degrees (range10-45) at maximal follow-up.

CONCLUSION:
In general sonographically detected isolated fetal hemivertebrae carry a good prognosis. Ultrasound appears accurate in the diagnosis of both the level and type of congenital malformation. The value of very early surgical management needs continued assessment.