Figure 5: Embryology of the normal spine (top), lateral hemivertebra (middle) and dorsal hemivertebra (bottom). In red, the normal ossification
centers, in green the defective ossification centers.
Associated anomalies
Hemivertebrae may be isolated or may occur in multiple areas within the spine and is frequently associated with other congenital anomalies6,7. Hemivertebra is commonly associated with other musculoskeletal anomalies including those of the spine, ribs, and limbs. Cardiac and genitourinary tract anomalies are the more common extra‑musculoskeletal anomalies seen with hemivertebra, with anomalies of the central nervous system and gastrointestinal tract also being reported. Hemivertebra may be part of a syndrome including Jarcho‑Levin, Klippel‑Fiel, and VACTERL. The incidence of karyotypic abnormalities in fetuses with isolated vertebral anomalies is thought to be small. In the largest series, Zelop et al. performed amniocentesis on 18 fetuses with isolated vertebral anomalies and obtained a normal karyotype in all 18 cases3.
Differential diagnosis
Hemivertebrae may have a similar ultrasonic appearance to the other vertebral abnormalities (wedge vertebra, butterfly vertebra, bloc vertebra, bar vertebra or any combination) that cause congenital scoliosis and in some cases may only be differentiated after careful neonatal radiologic evaluation. Open neural tube defects may also be associated with abnormal curvature of the spine but should have other findings differentiating it from hemivertebra. These include the intracranial changes associated with open neural tube defects as well as disruption of the skin over the defect and possibly the presence of a meningocele/myelomeningocele sac.
Prognosis
The prognosis is directly related to the presence or absence of associated anomalies. The prognosis of isolated hemivertebra is good. Left untreated, 25% of patients with congenital scoliosis show no progression, 50% progress slowly, and 25% progress rapidly during growth8. Spinal fusion is the treatment of choice for cases of congenital scoliosis that are progressive or are of the short, rigid type8. The treatment of congenital scoliosis should occur before significant deformity occurs.
Recurrence risk
The occurrence of isolated hemivertebrae in siblings is very uncommon. An association of hemivertebrae with neural defects in siblings has been reported. Wynne‑Davies performed a family survey on 337 patients with congenital scoliosis and found that 5 to 10% of sibling of patients with multiple vertebral anomalies with or without spina bifida had either vertebral anomalies or spina bifida4. However, she found only one of 245 siblings of 101 infants with a solitary vertebral defect (including isolated hemivertebra) had a spinal defect and concluded that isolated defects were sporadic (non‑familial) in nature and carried no risk to subsequent siblings. Connor et al. found an incidence of 4% of neural tube defects among siblings with congenital scoliosis7. In contrast to the previous report, they found an increased incidence of neural tube defects in siblings of probands with single hemivertebra as well as those with multiple vertebral defects.
Therefore, it would be reasonable to offer genetic counseling and prenatal diagnosis for neural tube defects to those patients with a previous child with vertebral anomalies.
Management
When the prenatal diagnosis of hemivertebrae is made, a meticulous search for associated anomalies should be performed. Chromosomal analysis can be offered, especially in the presence of associated anomalies. Amniotic fluid alpha‑fetoprotein concentration can be assessed if there is a question of an open neural tube defect and the patient is of appropriate gestational age. Serial ultrasonic evaluation is recommended to follow fetal growth and evaluate for signs of an open neural tube defect that may not be present at an initial early ultrasound.
If there are no other complicating factors, standard management of labor and delivery is recommended. A careful neonatal assessment for associated cardiac and genitourinary anomalies needs to be performed and the infant should receive long term orthopedic follow‑up so treatment can occur, if necessary, prior to the development of serious deformity.
References
1. Abrams SL, Filly RA: Congenital vertebral malformations: Prenatal diagnosis using Ultrasonography. Radiology 155:762, 1985.
2. Benacerraf B, Greene MF, Barss VA: Prenatal sonographic diagnosis of congenital hemivertebra. J Ultrasound Med 5:257‑259, 1986.
3. Zelop CM, Pretorius DH, Benacerraf BR: Fetal Hemivertebrae: Associated anomalies, significance, and outcome. Obstet Gynecol 81:412‑416, 1993.
4. Wynne‑Davies, R: Congenital vertebral anomalies: aetiology and relationship to spina bifida cystica. J Med Genet 12:280‑288, 1975.
5. Moore KL, Persaud TVN: The Developing Human, Fifth ed. Philadelphia: WB Saunders, 358‑364, 1993.
6. McMaster MJ, David CV: Hemivertebra as a cause of scoliosis. J Bone Joint Surg 68:588‑595, 1986.
7. Connor JM, Conner AN, Connor RAC, Tolmie JL, Yeung B, Goudie D: Genetic aspects of early childhood scoliosis. Am J Med Genet 27:419‑424, 1987.
8. Winter RB: Congenital scoliosis. Orthop Clin North Am 19:395‑408, 1988.