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1993-10-28-20 Hemivertebra © Gauthier www.thefetus.net/

Hemivertebra 

Daniel W. Gauthier, MD, William J. Meyer, MD

Address correspondence to: Daniel W. Gauthier, MD, Department of Obstetrics and Gynecology, Division of Maternal‑Fetal Medicine, University of Illinois College of Medicine, 820 South Wood Street, M/C 808, Room 250, Chicago, IL  60612‑7313, Ph: 312‑996‑7300 Fax: 312‑996‑4238

Synonyms: Congenital scoliosis (one of the causes of), unilateral aplasia of the vertebral body, complete unilateral failure of formation of the vertebral body.

Definition: Congenital malformation of the spine in which only half of a vertebral body develops.

Prevalence: 5‑10:10,000 births, occurs more commonly in females.

Etiology: Sporadic versus multifactorial inheritance.

Pathogenesis: Developmental failure of one of the lateral vertebral chondrification centers.

Associated anomalies: Musculoskeletal system including ribs, spinal cord and limbs. Other associated anomalies include cardiac, renal, central nervous system and gastrointestinal. May be part of a syndrome: Jarcho‑Levin, Klippel‑Fiel, VACTERL.

Differential diagnosis: Neural tube defects, other causes of congenital scoliosis (wedge vertebra, butterfly vertebra, bloc vertebra).

Prognosis: Dependant upon associated anomalies. Isolated hemivertebra carries good prognosis.

Recurrence risk: Rare, however, there may be a 4% risk of neural tube defects in siblings. 

Management: Dependant upon associated anomalies. Standard obstetrical management for isolated hemivertebra.

MESH Hemivertebra of thoracic vertebrae ICD9  756.14 CDC 756.155

Introduction

Congenital scoliosis is caused by the abnormal development of the vertebrae. Hemivertebra, a condition where there is complete unilateral failure of the vertebral body to form, is a common cause of congenital scoliosis. There are few reports concerning the ultrasonographic diagnosis of fetal hemivertebra1‑3.  We present a case of congenital scoliosis due to hemivertebra detected prenatally and the ultrasonic findings that led to the diagnosis.

Case report

A 30‑year‑old Hispanic woman, G2P1 was referred at 23 weeks gestational age for evaluation of a possible neural tube defect detected on an ultrasound performed elsewhere. The patient"s obstetrical history was unremarkable. The current pregnancy was complicated by poorly controlled class B diabetes. Her family history was significant for a brother with spina bifida. Our ultrasound revealed a singleton pregnancy with biometry consistent with 23 weeks gestational age. An abrupt change in the curvature of the spine was seen at the level of the twelfth thoracic vertebra (fig. 1).


Figure 1: Longitudinal view of the spine revealing abrupt change in curvature at approximately T12.

The overlying skin appeared intact and there were no intercranial findings suggestive of an open neural tube defect. Other anomalies identified included a shortened and bowed right tibia and bowed right fibula (fig. 2). 


Figure 2: Longitudinal view of the right lower leg demonstrating a bowed fibula (upper bone) and a shortened and bowed tibia (lower bone).

A single umbilical artery was also seen. The patient was counseled on the findings and elected to have an amniocentesis. Chromosomal analysis revealed a normal 46 XX, karyotype and amniotic fluid alpha‑fetoprotein concentration was 1.1 multiples of the median.

Serial ultrasound examinations revealed normal growth and no change in the above findings. The patient went into spontaneous labor at 37 weeks gestation and had a normal vaginal delivery of a female infant with a birthweight of 3254g and Apgar scores of 7 and 8. Examination of the umbilical cord confirmed the single umbilical artery.

Neonatal chest X‑ray revealed hemivertebra of T11 and a malformed twelfth thoracic vertebra (fig. 3). X‑ray of the right lower leg confirmed an abnormal tibia (fig. 4). The infant was discharged home on the fifth day of life with follow‑up care scheduled with pediatric orthopedic surgery.


Figure 3: Neonatal X-ray of figure 2.


Figure 4: Neonatal chest X-ray revealing hemivertebra of T11 and  abnormal twelfth thoracic vertebra.

Discussion

Hemivertebra is an uncommon congenital anomaly of the spine in which only one half of the vertebral body develops. The incidence of hemivertebra is estimated at 5‑ 10:10,000 births with a male/female ratio of 0.31 for multiple vertebral anomalies and 0.68 for solitary vertebral anomalies4.

Pathogenesis

At 6 weeks gestational age, 2 lateral chondrification centers arise in the developing vertebral bodies. These chondrification centers then unite by 7 to 8 weeks gestational age to form the primary ossification center of the vertebral body. A hemivertebra results from the failure of one of the lateral chondrification centers to develop5. The defective vertebra acts as a wedge in the spine leading to excessive lateral curvature (sco­liosis) (fig. 5).


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.

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