Butterfly vertebra: Anomaly of the spine

butterfly vertebra

Article reviewed and approved by Dr. Ibtissama Boukas, physician specializing in family medicine

First described in 1844, the vertebrate butterfly is an uncommon birth defect of the spine. Often asymptomatic, it is sometimes responsible for lumbar or back pain. In this article, we will discover the characteristics of this type of vertebra, and how the diagnosis is generally made.

Definition

The vertebrae butterfly is a rare congenital malformation resulting from a defect in ossification of the vertebral body normally accomplished between the third and sixth week of gestation. As a result, the vertebrae and intervertebral discs located above and below the affected vertebra compensate by adjusting their shape.

Moreover, it is sometimes confused with a metastatic tumor, a compression fracture traumatic cause or due to osteoporosis, or an infection.

The anomaly mainly affects the lumbar region, then the back, and rarely affects the cervical vertebrae. As it is often asymptomatic, it is often discovered incidentally during an examination ofmedical imaging. On the other hand, the butterfly vertebra can modify the normal biomechanics of the spine, and cause lower back pain. Also, it increases the risk of herniated disc.

Due to the rarity of this condition, there are no epidemiological data linking butterfly vertebra and low back pain (or other spinal pain).

Despite being generally benign, butterfly vertebra can sometimes coexist with other birth defects. Indeed, congenital malformations of the spine are often associated with cardiac and urogenital abnormalities. We can also find abnormalities such as:

  • other spinal abnormalities
  • anal atresia
  • heart abnormalities
  • a tracheoesophageal fistula
  • kidney abnormalities
  • limb abnormalities
  • etc.

In addition, intraspinal abnormalities (such as those related to spinal cord) may coincide with vertebral malformations such as butterfly vertebrae. This represents more than a third of adolescents with congenital scoliosis.

Diagnostic

On the anteroposterior X-ray, the butterfly vertebra is easily detected because it is divided into two hemi-vertebrae. The latter are generally symmetrical, but can also be of different size in the case of scoliosis. These two hemi-vertebrae also resemble the wings of a butterfly, hence the name.

If in doubt about the diagnosis, a CT scan and magnetic resonance imaging (MRI) are recommended to rule out other birth defects. One thinks for example of the supernumerary lumbar vertebrae, the spina bifida, scoliosis, etc.

Furthermore, we mentioned that the butterfly vertebra was sometimes accompanied by cardiac or urogenital abnormality. It is therefore common for the doctor to continue the investigation via a cardiac and renal evaluation when a butterfly vertebra is discovered on imaging. 

References

  • https://pubs.asahq.org/anesthesiology/article/129/3/582/22261/Butterfly-Vertebrae
  • https://www.reumatologiaclinica.org/en-butterfly-vertebra-articulo-S2173574314000550
Back to top