Butterfly vertebra: A case report

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Journal of Clinical Imaging 25 (2001) 206 – 208

Butterfly vertebra: A case report ¨ ztu¨rka, Is¸ik Bo¨kesoyb Birkan Sonela,*, Peyman Yalc¸ina, Erhan Arif O a

Department of Physical Medicine and Rehabilitation, Ankara University Medical School, Kirkpinar sokak, No: 25/8, 06540, Ankara, Turkey b Department of Genetics, Ankara University Medical School, Ankara, Turkey Received 20 January 2001

Abstract Butterfly vertebra is a rare congenital anomaly associated with syndromes such as Pfeiffer, Jarcho-Levin, Crousen, Alagille. In the literature, only a few cases of butterfly vertebra have been reported as incidental finding. We described a 37-year-old male who had an L3 butterfly vertebra associated with an L4 – L5 disc protrusion. Awareness of this anomaly is important for making correct diagnosis. Although this uncommon anomaly is considered to be usually asymptomatic, we suggest that it might increase the incidence of disc herniation, because the condition may alter the spinal biomechanics. D 2001 Elsevier Science Inc. All rights reserved. Keywords: Butterfly vertebra; Anomaly; Spine; Embryology; Skeletal anomalies

1. Introduction

2. Case report

Although congenital vertebral abnormalities are common, symmetric fusion defects leading to butterfly vertebra are not frequent in the general population [1]. This defect is considered to occur between the third and sixth week of gestation. Developing vertebral bodies have two lateral chondrification centers that would normally fuse. If one fails to develop completely, a hemivertebra results. Failure of the two centers to fuse, however, results in the formation of a butterfly vertebra. A butterfly vertebra may associate with a few syndromes [2 –5] and chromosome deletions [6– 8]. Presently, only a few cases of butterfly vertebra are reported as an incidental finding. It may be asymptomatic for long periods, but when discovered other body systems are carefully evaluated that may have been affected during embryogenesis [1].

A 37-year-old male was seen in our clinic for low back and left leg pain. He was treated for 2 years in other clinics for these symptoms. He indicated that his pain was aggravated by standing and bending. On examination, the patient had slight right bending scoliosis. Ranges of motion of the thoracolumbar spine were normal. Straight leg raise test was positive on the left, creating leg pain at 60°. Deep tendon reflexes at the patella and heel were + 2 bilaterally and were equal and, no motor weakness and normal sensory response were found. Other systems and results of blood tests were normal. The clinical findings of the patient were in agreement with the lumbar disc disease. Anteroposterior (AP) lumbosacral X-ray revealed a butterfly-like image at the L3 vertebra, and Type 4 mixed sacralization at the L5 vertebra (Fig. 1). The image at the L3 vertebra was thought to be a compression fracture or congenital anomaly, i.e., butterfly vertebra on differential diagnosis. Magnetic resonance imaging confirmed the presence of this anomaly and also revealed the L4 – L5 left disc protrusion (Fig. 2a and b). Electromyography was performed. There were slight chronic L5 radiculopathy findings on the left side.

* Corresponding author. Tel.: +90-312-4381662; fax: +90-3125620116. E-mail address: [email protected] (B. Sonel).

0899-7071/01/$ – see front matter D 2001 Elsevier Science Inc. All rights reserved. PII: S 0 8 9 9 - 7 0 7 1 ( 0 1 ) 0 0 2 6 6 - 2

B. Sonel et al. / Journal of Clinical Imaging 25 (2001) 206–208


condition may occur more frequently than recognized previously. They reported the skeletal findings in 108 patients with a 22q11.2 deletion, of whom 37 (36%) had a skeletal anomaly. Butterfly vertebrae were noted in 11% of 63 patients. Anomalies have been reported in patients with monosomy 20p and 20p-mosaicism as well. But in these karyotypes, the clinical picture is severe and is characterized by a flat face, flat nasal bridge, small ears with thick overfolded helices, chest deformity, and butterfly vertebra [7,8]. Although the present case had only vertebral anomalies (butterfly vertebra and sacralization) and the other system examinations were normal, all of these syndromes and

Fig. 1. AP radiograph of the lumbosacral spine, showing the appearance of the butterfly vertebra at L3 and Type 4 mixed sacralization at the L5 vertebra.

Chromosomal analysis was demonstrated to be 46,XY karyotype, which was done to find out if there were any chromosome anomalies accompanying the butterfly vertebra. Cervical and chest X-ray and abdominal ultrasonography were normal.

3. Discussion A butterfly vertebra is said to be the result of a sagittal cleft caused by the persistence of the notochord. It is often associated with rib and/or vertebral anomalies such as bars, supernumerary lumbar vertebrae, and spina bifida [9]. Butterfly vertebrae are seen in patients with Pfeiffer’s syndrome [3], Jarcho-Levins (spondylothoracic or spondylocostal dysostosis) Syndrome [5], Crouzon Syndrome [4], Alagille Syndrome [2]. Most cases with diastematomyelia are seen in association with other anomalies of the vertebral column such as spina bifida, kyphoscoliosis, and butterfly vertebra [10]. Skeletal anomalies have been reported in patients with a 22q11.2 deletion. Ming et al. [7] suggested that this

Fig. 2. (a) Magnetic resonance imaging of the lumbar region. L3 butterfly vertebra is seen. (b) Magnetic resonance imaging of the lumbar region confirmed the presence of the L3 butterfly vertebra and L4 – L5 disc protrusion.


B. Sonel et al. / Journal of Clinical Imaging 25 (2001) 206–208

conditions as mentioned above were considered in the differential diagnosis. Therefore, he was evaluated at the Department of Genetics and his karyotype designation was normal. In the lateral radiograph, the butterfly vertebra shows either trapezoidal or cuneiform anterior wedging, which may be confused with compression fracture, because wedging is the most obvious radiological sign of a hyperflexion compression fracture. Since fracture needs immediate treatment, it is important to make a differential diagnosis between the two conditions. In osteoporosis, wedging, biconcavity, and compression may all be apparent. Vertebral compression is frequently combined with wedging. Both wedging and compression in osteoporosis indicate a fracture of the vertebral body. The weakened and brittle bone leads to more irregular collapse, and the upper and lower margins of the vertebrae are not involved to similar degrees. Extensive osseous destruction in neoplasm and infection can lead to irregular vertebral collapse. In infection, discal destruction with disc space narrowing is characteristic [11]. Although in the lateral radiograph butterfly vertebra is wrongly reported as wedge fracture, the correct diagnosis is made in the AP radiographs [12]. The butterfly vertebra is easily detected in an AP radiograph, because the vertebra is split into lateral halves or hemivertebra, usually of the same size, which look like the wings of a butterfly in AP X-ray views [11]. There are two chondral centers separated by an empty space, the posterior and inferior surfaces of both half bodies are depressed at their centers. The vertebrae below may have a slight compensatory enlargement of its body [13]. In doubtful cases, anterior tomography is also indicated [12]. Delgado et al. [14], while presenting a patient with L3 butterfly vertebra and lumbar disc protrusion, have reported that this rarely seen anomaly was usually asymptomatic and of no clinical significance and was found coincidentally. The patient presented here similarly has L3 butterfly vertebra and L4 – L5 disc protrusion. In addition to those, he had Type 4 mixed sacralization [15]. Type 4 mixed sacralization exhibits Type 2 (pseudoarticulation) on side and Type 3 (bone fusion) on the other side. Sacralization of the fifth lumbar vertebra is unlikely to cause symptoms when the entire vertebra is solidly incorporated into the sacrum. Occasionally, only one transverse process articulates with the sacrum, altering spinal mechanics and resulting in severe instability and stress. Type 4 does not prove any higher incidence of disc herniation above the transitional segment. Although butterfly vertebra is considered usually asymptomatic, we think it might increase the incidence of disc

herniation, because there is absence of a normal disc between the two vertebrae. This condition may alter the spinal biomechanics. Moreover, if a congenital reduction or lack of vascularisation is also present, the butterfly vertebra is associated with anterior aplasia, which may be associated with kyphosis. It is potentially serious because compression of the spinal cord sometimes develops [16]. All these should be investigated in detail with biomechanical studies and on a large population of butterfly vertebrae.

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