Hemivertebra

A hemivertebra is type of vertebral anomaly and results from a lack of formation of one half of a vertebral body. It can be a common cause of a congenital scoliosis / kyphosis or a lordosis. 

Epidemiology

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

Pathology

It falls under the spectrum of segmentational 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

Recognised associations are many and include

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

^{This list supposed to be lot longer that this. If you know more, do add in with a relevant journal reference :)}

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 segemental : 
  • not seperated 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 a kyphosis
• lateral hemivertebra : classically results in a scoliosis
• ventral hemivertebra (extremely rare) : results in the 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 at either side of the vertebral column ⁵.

Plain film / CT

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

Prognosis

The prognosis can be variable dependant on the type from being a progressive to non progressive deformity. The strongest negative impact is when a hemivertebra occurs at the lumbo-sacral level ⁷.

Differential diagnosis

For antenatal sonographic appearances consider 

• block vertebra