Vanishing vertebra: A rare finding in sickle cell disease

A 28-year-old male with sickle cell disease and recent vaso-occlusive crises presented with a new episode of back pain and low-grade fever. The pain was managed with NSAIDs and morphine, but there was an incomplete response. Laboratory findings revealed leucocytosis with neutrophilia and elevated markers of haemolysis. Empirical antibiotic therapy was started after a blood culture was taken, and a spinal MRI was requested.

Spinal MRI showed diffuse bone marrow infiltration, with signal intensity decrease on both T1 and T2 sequences compared to vertebral discs, indicating reconversion from yellow marrow to bone marrow. Additionally, multiple areas of low signal intensity within vertebral bodies on T1-weighted images and high signal intensity on T2-weighted images suggested vertebral bone infarcts (Figure 1).

Vertebral bodies exhibited an “H-shaped” morphology with central depression, and two thoracic vertebrae were almost completely collapsed (Figure 2). Interestingly, different counting methods led to discrepancies in identifying the collapsed vertebral bodies. When counting upwards from the lumbar region (L5), the collapsed vertebral bodies were identified as T6 and T10. However, counting downwards from the uppermost cervical level (C2) identified them as T5 and T9, highlighting a lack of correspondence (Figure 3).

Sagittal sequences showed posterior elements at T5/T6 without a body or disc, articulating with the uppermost collapsed vertebra’s facets. No lumbosacral transition anomalies were detected (Figure 4).

In total, upon counting all vertebral bodies, 28 were identified instead of 29, with the T5 vertebra completely absent, leaving only its posterior elements.

Background

Sickle cell disease (SCD) is a haemoglobinopathy characterised by the presence of haemoglobin S (HbS), inherited in an autosomal recessive manner. The abnormal morphology of HbS reduces the flexibility of red blood cells, making them rigid. As a result, these cells have a tendency to accumulate in capillaries, leading to vessel occlusion and subsequent ischemia, which manifests as vascular occlusive crises [1].

Clinical Perspective

Sickle cell disease predisposes individuals to vaso-occlusive crises, which can lead to ischemic events and infarctions affecting multiple organs, including the bones. Within the spine, such vaso-occlusive incidents can cause bone infarctions within vertebral bodies, resulting in the phenomenon known as “vanishing vertebra”. This phenomenon may be exacerbated by the collapse of neighbouring vertebrae, potentially leading to spinal deformities and neurological compromise.

Acute presentations include bony infarctions associated with vaso-occlusive crises and osteomyelitis, while chronic complications encompass osteoporosis, compression fractures, and osteonecrosis [1,2].

Imaging Perspective

In individuals with SCD, haematopoietic marrow hyperplasia leads to the conversion of yellow marrow to red marrow, which is evident as abnormal signal intensity on T1-weighted images due to the absence of normal fatty signal. Osteonecrosis, a consequence of bone infarction following ischemia, initially presents with increased T2 signal in the acute phase and transitions to a fibrotic/sclerotic pattern with low signal on all sequences in the chronic phase [2,3].

The vanishing vertebra phenomenon, characterised by the complete disappearance of one or more vertebral bodies, is exceedingly rare. Typically, the posterior elements remain intact. Our case represents the first report demonstrating MRI images of this entity; previous literature only included radiographic evidence [4].

The aetiology of vanishing vertebra involves a complex interplay of factors, including vaso-occlusive infarction, secondary infection, compressive forces, and reactive bone changes. Presentations may include multiple osteolytic lesions in the lumbar vertebrae with reduced vertebral body height [3].

In our case, the patient’s history of SCD and the imaging findings of vanishing vertebra support the diagnosis. Accurate differentiation from other causes of vertebral collapse, such as infection or neoplasm, is crucial.

In osteomyelitis, findings such as vertebral body oedema, paraspinal/epidural abscesses, or disc involvement would be expected [2].

Outcome

The management of vaso-occlusive crises primarily focuses on pain management using analgesics, while simultaneously investigating potential infectious sources such as osteomyelitis. Therefore, empirical antibiotic therapy is usually initiated pending confirmation through analytical, clinical, and imaging assessments.

Percutaneous vertebroplasty has been documented as an effective and safe intervention for alleviating back pain associated with vertebral compression fractures [5].

Take Home Message / Teaching Points

Vanishing vertebra is a rare yet significant complication of SCD, highlighting the importance of meticulous radiological assessment to prevent oversight or misinterpretation as anatomical variations or fusion anomalies.