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Imaging Diagnosis

Radioisotope scanning, using technetium, will show increased activity in any joint, particularly in the spine early in the infection, before there are other imaging changes. Gallium has been used to assess activity, but its accuracy remains controversial.

The most characteristic radiological findings are seen in the spine, especially in the lower dorsal and lumbar regions, but even these are nonspecific. The lesions may occur at the periphery or in the center of the vertebral body. Peripheral vertebral lesions tend to occur early in the infection and affect the anterosuperior margin of the vertebral body, causing rarefaction or erosion and loss of cortical definition; there is rounding of the corner of the vertebral body with eventual resorption. Loss of the intervertebral disc space occurs early (Figs. 32.2 thru 32.4) and is always associated with destruction of cancellous bone, although this may need CT or conventional tomography to be clearly demonstrated.

In most countries, there is less suppuration in brucellosis than in tuberculous infections, although the frequency of paraspinal abscesses displays some geographic variation. When a paraspinal abscess does develop in brucellosis it is less prominent than that seen in tuberculosis and very seldom undergoes calcification, an important differentiating feature. The abscesses may be unilateral or bilateral; they are seldom very large and are well demonstrated by CT or MRI. There is no accurate way to differentiate between the abscess of brucellosis and that of tuberculosis.

In all cases of brucellosis, there is evidence of bone repair at an early stage. There is reactive sclerosis and proliferation of new bone with spur formation (Fig. 32.3), particularly anteriorly or laterally, and only rarely posteriorly. The result is a hypertrophic spondyloarthritis. Occasionally, there is a small loose fragment of bone anterior to the original defect, with subsequent sclerosis around it. All these radiological changes may affect one or more vertebrae. The anatomical, pathological, and plain radiographic findings have been well correlated by Botet. The central type of vertebral lesions is less common than the peripheral type and causes deep semicircular erosions, or multiple small defects within the vertebral body, resulting in a honeycomb pattern. These heal with dense irregular bone, but hollow defects may persist. It is in this pattern of infection that collapse of the vertebral body occurs with varying degrees of wedging.

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Fig. 32.2A-C. Acute brucellosis in a 40 year-old Saudi male complaining of fever, joint pains, and, particularly, pain in the back (A) The lateral view of the lumbar spine shows loss of joint space between the first and second lumbar vertebrae, with gas in the intervertebral disc and early destruction of the body of the second vertebrae anteriorly. There is osteophyte formation anteriorly. (B,C) CT scans confirm the anterior vertebral destruction, central necrosis, and some new bone formation. There is minimal paraspinal soft tissue involvement. The patient was found to have a high brucella titer.(Courtesy of Dr. Frank McGuinness, Saudi Arabia).

Fig. 32.3. Brucellosis of the lower thoracic spine showing two central destructive lesions in adjacent vertebrae (T8 and T9). Below this, T 10 shows dense reactive sclerosis as healing starts. The disc spaces between T 9 and T 10, and T 10 and T11 are narrowed and there is slight hypertrophic spurring showing anteriorly on these vertebrae. There is also anterior scalloping of the T9 and T10 vertebral bodies due to pulsation of the aorta transmitted through a paraspinal abscess.

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Fig. 32.4A-D. Chronic brucellosis in a 70 year-old man from Saudi Arabia. A Loss of joint space, reactive sclerosis and osteophyte formation, and irregularity of the L4 and L5 vertebral bodies. There are similar changes in the upper lumbar vertebrae and at the patient's age it is difficult to sure of their cause; there is no loss of the intervertebral disc space at this level. B-D T 1- and T 2-weighted MRI scans confirm the loss of the L4-5 disc space with residual bony destructive-repair changes in both the vertebral bodies. These scans also show the epidural involvement. The patient had a high brucella titer. (Courtesy of Dr. Frank McGuinness, Saudi Arabia).

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