Hemivertebra

Hemivertebra is a type of vertebral anomaly and results from a lack of formation of one half of a vertebral body. It is a common cause of congenital scoliosis. 

Epidemiology

The estimated incidence is at ~0.3 per 1000 live births ².

Pathology

It falls under the spectrum of segmentation anomalies and can involve one or multiple levels.

A hemivertebra acts as a wedge within the vertebral column, resulting in curvature away from the side on which it is present. 

Associations

Recognized associations are many and include:

• Aicardi syndrome
• cleidocranial dysostosis
• gastroschisis ³
• Gorlin syndrome
• fetal pyelectasis ³
• Jarcho-Levin syndrome
• OEIS complex
• VACTERL association
• mucopolysaccharidosis ⁹

Classification

A hemivertebra can be classified according to many types which include:

Attachment

• fully segmental (free)
  • not attached to either vertebra above or below
  • most concerning
• semi segmental: half segment is fused with vertebra above or below with no intervening intervertebral disc
• non-segmental
  • not separated from (i.e. connected to) either level above or below
  • causes less of a concern
• incarcerated
  • joined by pedicles to levels above and below
  • causes less of a concern

Orientation 

• dorsal hemivertebra: classically results in kyphosis
• lateral hemivertebra: classically results in scoliosis
• ventral hemivertebra (extremely rare): results in lordosis

Radiographic features

Antenatal ultrasound

A hemivertebra may be seen as an asymmetrical vertebral body on sagittal or coronal scanning, while on axial scanning, a focal defect may be seen on either side of the vertebral column ⁵.

Plain radiograph / CT

Usually directly outlines the bony anomaly and is often seen as a wedge-shaped vertebral body.

Treatment and prognosis

The prognosis can be variable dependent on the type of segmentation anomaly, from being a progressive to a non-progressive deformity. The strongest negative impact is when a hemivertebra occurs at the lumbosacral level ⁷.

Differential diagnosis

Consider

• block vertebrae
• bullet shaped vertebrae
• butterfly vertebrae