What is the role of MRI in the workup of sickle cell disease (SCD)?

Updated: Jul 24, 2019
  • Author: Ivan Ramirez, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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Answer

Answer

MRI allows the early detection of changes in bone marrow due to acute and chronic bone marrow infarction, marrow hyperplasia, osteomyelitis, and osteonecrosis. As with plain radiography, the sine qua non of diagnosing osteomyelitis on MRI is the identification of cortical destruction for which MRI is exquisitely sensitive. [19, 19, 5, 20, 9]

Differentiation of bone infarct from osteomyelitis is one of the most challenging issues in the evaluation of acute bone pain in patients with SCD. Atypical findings on diffusion-weighted images have been identified in the early phase of presentation and can help differentiate bone infarct from osteomyelitis. [11]

Acute infarction is characterized by diffuse decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images. This change results from bone marrow edema. With time, the process becomes focal, and T1-weighted images show a serpentine line of low signal intensity surrounding hyperintense marrow (see the images below). A double line of low signal intensity surrounding inner high signal intensity is sometimes seen on T2-weighted images.

Bone marrow hyperplasia in patients with sickle cell disease presents as diffuse areas of intermediate signal intensity on T1-weighted images, similar or slightly higher than that of skeletal muscle, and corresponding mildly increased signal on T2-weighted images. This effect is due to the replacement of fatty marrow by hematopoietic marrow.

Chronic bone infarcts, or old infarction and fibrosis, appears as focal areas of decreased signal intensity on both T1- and T2-weighted images. [21]  With osteomyelitis, areas of bone infection demonstrate low signal intensity that replaces the usual high signal intensity of fatty marrow on T1-weighted images. This appears as areas of increased signal intensity on T2-weighted images and results from bone marrow edema and/or bone destruction. Bone sequestra, sinus tracts, and subperiosteal abscesses are also clearly identified when present. Fat saturated T1-weighted images with intravenous gadolinium facilitate the identification of bone sequestra, which present as focal low signal intensity defects surrounded by avidly enhancing inflammatory tissue. [9]

Skeletal sickle cell anemia. Osteonecrosis. Corona Skeletal sickle cell anemia. Osteonecrosis. Coronal T1-weighted MRI shows a slightly flattened femoral head with a serpentine margin of low signal intensity around an area of ischemic marrow with signal intensity similar to that of fat.
Skeletal sickle cell anemia. Osteonecrosis in the Skeletal sickle cell anemia. Osteonecrosis in the same patient as in the previous image. Coronal T2-weighted MRI shows a serpentine area of low signal intensity and additional focal areas of abnormal low signal intensity in the femoral head; these findings reflect collapse of bone and sclerosis.

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