Physicians Should Keep in Mind Possibility of Butterfly Vertebrae

Your spine is made up of small bones that stack one on top of the other. These are called vertebrae. Some people have a benign (not harmful) abnormality called butterfly vertebrae. Butterfly vertebrae have a cleft, an indentation or opening, through the middle. If you look at it with an x-ray, the shape reminds you of a butterfly. Usually, this doesn't cause any problems and goes undetected unless there is a reason to x-ray that part of the back. Sometimes, however, there may be pain, but not from the abnormality itself.

The authors of this article described a 46-year-old woman who had lower back pain, made worse by bending forward or standing for long periods. When she had an x-ray, the doctors saw butterfly vertebrae in the middle section of the back, the thoracic spine, but this was just a coincidence because the pain was actually being caused by pressure between two nearby discs. Her doctors treated her for lower back pain and she was assured that although she had been diagnosed with the abnormality, there was no need for any treatments.

Researchers believe that the butterfly vertebrae occur when the fetus is between three and six week gestation and, although most butterfly vertebrae are in the lumbar spine (the lower part of the back), the can happen in other parts, as with the patient just described. There are some syndromes that may also have this abnormality, such as Alagille syndrome (arteriohepatic dysplasia>), Pfeiffer syndrome, Crouzon syndrome, and Jarcho-Levin syndrome. Since the patient in the case study didn't have any signs of any of the syndromes, nor did she have any other back abnormalities, like spina bifida, diastematomyelia, or kyphoscoliosis, the doctors felt that her condition was benign.

The authors point out that butterfly vertebrae can be easily confused with a fracture on an x-ray, but magnetic resonance imaging (MRI), which can show images of soft tissue, show that there is no soft tissue damage around the vertebrae, which means there's no break in the bone. Although the actual butterfly vertebrae doesn't cause pain, it can protrude (stick out) enough to cause the spine to be a bit out of line. This alteration in alignment can end up causing back pain. The authors discuss one patient who had butterfly vertebrae in the lumbar spine but complained of pain in the thoracic spine.

The authors also write that although thoracic butterfly vertebrae are rare, they do occur. So if a doctor is examining a patient for back pain, they should carefully examine the x-rays and MRIs to see if there's any evidence of trauma. If there isn't, there's a good chance what the doctor is seeing is the butterfly vertebrae. By recognizing this possibility, patients could be spared unnecessary tests and perhaps even surgery.

Reference: 

Gopinathan Patinharayil, MD, DOrthos, MS Ortho, DNBOrtho, MNAMS, et al. Butterfly Vertebrae. In Spine. November 2008. Vol. 33, No. 24. Pp. E926-928

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