Hemivertebrae are congenital anomalies of the spine, present at birth. The condition arises from a vertebra failing to develop correctly in the womb, resulting in a partially formed, wedge-shaped bone. This contrasts with the rectangular shape of a healthy vertebra and can disrupt the spine’s normal alignment. While it is a developmental defect, the severity and implications can vary widely.
Causes and Development
The formation of a hemivertebra is an error that occurs early in embryonic development when the spine is forming. It is a failure of segmentation, where the ossification centers of a vertebral body do not properly fuse. This results in one side of the vertebra failing to form completely, meaning the condition is not caused by injury after birth.
While the precise cause is often unknown, it involves a mix of genetic and environmental influences. In humans, hemivertebrae can be associated with genetic syndromes that affect skeletal development, like Jarcho-Levin or Klippel-Feil syndrome. The condition is also an inherited trait in certain animal breeds, particularly in brachycephalic (short-nosed) dog breeds like French Bulldogs, English Bulldogs, and Pugs, where selective breeding has increased its prevalence.
Associated Symptoms and Conditions
The wedge-shaped vertebra disrupts the spine’s mechanical balance, often leading to abnormal curvatures. A lateral (sideways) curve is known as scoliosis and is the most common deformity. A forward rounding of the upper back is called kyphosis (hunchback), while an inward curve of the lower back is lordosis (swayback). The specific type of curve depends on the location and orientation of the malformed vertebra.
In many instances, an individual may have no noticeable symptoms if the defect is balanced or non-progressive. If the spinal deformity is severe or progresses, it can lead to compression of the spinal cord or nerve roots. This can cause neurological symptoms such as pain, muscle weakness, numbness, or problems with bladder or bowel control. Common physical signs include uneven shoulders, a tilted rib cage, or one shoulder blade appearing more prominent.
The progression of the spinal curve is a concern. Statistics suggest that about 25% of these curves remain stable, 50% progress slowly, and 25% can worsen rapidly. The location of the hemivertebra also plays a part in its impact, as a malformation in the lumbosacral region at the base of the spine can have a more significant effect.
Diagnostic Process
Diagnosis begins with a physical examination followed by medical imaging. X-rays are the standard tool, providing clear images of the bones to identify the wedge-shaped vertebra. This imaging allows a doctor to measure the degree of any resulting spinal curvature, like scoliosis or kyphosis, and establish a baseline for monitoring.
For a more detailed assessment, advanced imaging may be used. A computed tomography (CT) scan generates a detailed, three-dimensional view of the vertebrae, showing the anomaly’s shape and size. To evaluate soft tissues, a magnetic resonance imaging (MRI) scan is used to assess the spinal cord and nerves for compression. In some cases, the condition may be detected before birth through prenatal ultrasound.
Management and Treatment
The management strategy is tailored to the individual, depending on the curve’s severity and likelihood of progression. For mild cases without symptoms or worsening signs, the approach is observation. This involves regular check-ups and periodic X-rays to monitor the spine, especially during a child’s growth spurts.
When a spinal curve progresses in a growing child, a back brace may be recommended. This non-surgical option helps guide the spine’s growth and prevent the curvature from becoming more severe. The custom-fitted brace must be worn for a prescribed number of hours daily and aims to halt the curve’s advancement, not correct it.
Surgery is considered for severe, rapidly progressing deformities or when there is spinal cord compression. A common procedure is a hemivertebra excision, where the malformed vertebra is removed. This is often combined with spinal fusion, where adjacent vertebrae are joined with rods and screws to create a stable segment, correcting the deformity.
Living with Hemivertebrae
The long-term outlook for an individual with a hemivertebra depends on the severity of the condition. Many people with a single or non-progressive hemivertebra live full and active lives with few limitations. If the spinal curvature is mild and does not worsen, it may not require treatment beyond the periodic monitoring discussed previously. The prognosis is good when the hemivertebra is an isolated issue.