Imaging the bone marrow with magnetic resonance during a crisis and in chronic forms of sickle cell disease

The radiological manifestations of sickle cell disease

Sickle cell disease (SCD) is an inherited abnormality of the beta-globin chain, which causes a spectrum of haemolytic anaemias. Clinical manifestations in SCD include anaemia, jaundice, recurrent vaso-occlusive crises, and infections (particularly by encapsulated bacteria) due to functional asplenia and cerebrovascular accidents. Radiological investigations play a critical role both in the diagnosis and in the primary prevention of the complications of SCD.

Bone involvement in sickle cell disease

Bone involvement is the commonest clinical manifestation of sickle cell disease both in the acute setting such as painful vaso-occlusive crises, and as a source of chronic, progressive disability such as avascular necrosis. Management of these problems is often difficult because of the diagnostic imprecision of most laboratory and imaging investigations and because of the lack of evidence for most surgical procedures in sickle cell disease. This review first discusses the acute problems related to bone involvement in sickle cell disease, with particular reference to differentiating infection from infarction, and then describes the long-term effects of sickle cell disease on bone mineral density, growth, and chronic bone and joint damage.

Perivascular fibrosis in the bone marrow in sickle cell disease

CONTEXT

Magnetic resonance imaging of bone marrow in homozygous sickle cell disease (hemoglobin [Hb] SS) shows nonhomogeneous, mottled signals that increase with age and number of crises. The pattern of these signals is reminiscent of the underlying vascular architecture, but histopathology of this tissue has not been adequately studied.

OBJECTIVE

To elucidate the histopathology of blood vessels in the bone marrow in sickle cell disease.

DESIGN

Retrospective histochemical morphometric study of bone marrow arteries by point counting in HbSS (13 cases) and sickle cell Hb C (HbSC) (8 cases) compared to nonanemic normal controls (HbAA) (10 cases). All patients were nondiabetic, normotensive, younger than 37 years, and matched for age group.

RESULTS

The mean point count for perivascular fibrous tissue was significantly greater in the HbSS group (P <.001) in both small (P <.001) and medium-sized (P =.002) vessels, and in both age groups (pediatric, P <.001; adult, P =.005) compared with the HbAA group. Additional analysis showed the difference was significant in HbSS pediatric small vessels (P <.001) and in pediatric and adult medium vessels (P =.045 and P =.03, respectively). Ratios of fibrous tissue to muscle showed proportionately greater fibrous tissue in HbSS pediatric small (P <.001) and medium-sized vessels (P =.02), and in adult large vessels (P =.03). Mean point counts for muscle were significantly decreased in HbSS small vessels when all ages were compared as a group (P =.02), but when compared by age groups, counts were significantly increased in adult HbSS medium-sized vessels (P =.01). Overall mean point counts for muscle and fibrous tissue in the HbSC group were intermediate between those of the HbSS and HbAA groups, but were not significantly different from counts in the HbAA group (P =.78 and P =.35, respectively).

CONCLUSION

In sickle cell disease, arterial vessels in the bone marrow show significantly increased fibrous connective tissue and changes in muscle that vary with age and vessel size.

The role of CT and MR in imaging the complications of sickle cell disease

Sickle cell disease is the most common inherited haemoglobinopathy described. Complications of sickle cell disease (SCD) are due to chronic haemolysis of fragile red cells or secondary to vascular occlusion by sickled red cells with subsequent tissue infarction. Traditionally plain film radiography has been the mainstay in the assessment of patients with SCD, but increasingly magnetic resonance (MR) imaging and computed tomography (CT) are being used. In this review the imaging features of a range of complications of SCD are demonstrated with particular emphasis on CT and MR.

Gadolinium-DOTA enhanced MRI of painful osseous crises in children with sickle cell anemia

In order to evaluate the role of gadolinium-DOTA enhanced MRI in the management of painful osseous crises in children with sickle cell anemia (SCA), nine children with SCA underwent MRI, bone scans and ultrasonographic studies during 11 osseous crises. Imaging findings were compared with the final diagnosis: three acute osteomyelitis (AO) and 16 acute infarcts (AI). MRI could not differentiate AO from AI. The appearance of severe AI was very misleading and was similar to the usual appearance of AO, including soft tissue changes, periosteal reaction and patterns of enhancement. Gadolinium-DOTA enhanced MRI was useful for determining the anatomic site and extent of AO or AI and for distinguishing between necrotic material, fluid collection and vascularized inflammatory tissue. It can also help to guide the aspiration of intraosseous, subperiosteal and soft tissue fluid collections.