venerdì 11 luglio 2008
Sickle cell disease with Moyamoya picture
Figure 1: Axial T1 weighted images demonstrates expansion of the diploic space consistent with extramedullary hematopoesis, a finding identified in hemoglobinopathies such as sickle cell disease and thalassemia.
Figure 2: FLAIR images demonstrate areas of increased signal in the left frontal white matter indicating ischemic changes.
Figure 3: Gradient echo image demonstrates increased susceptibility in the left centrum semiovale indicating hemosiderin deposition resulting from prior hemorrhage.
Figure 4, Figure 5, Figure 6: Diffusion weighted images demonstrate scattered areas of restricted diffusion, indicating acute infarcts in a watershed distribution in the left internal carotid artery territory.
Figure 7: MR angiography demonstrates absence of the anterior cerebral arteries with narrowing of the distal left internal carotid artery accounting for the acute scattered infarcts in the left internal carotid territory.
Diagnosis: Sickle cell disease with Moyamoya picture
Sickle cell disease is a hemoglobinopathy where abnormal strands of hemoglobin (Hgb S) stiffen when deoxygenated. This results is deforming of erythrocytes which produce microvascular occlusion and hence, ischemic changes. Because of abnormal adherence of sickled erythrocytes, they deform the internal elastic lamina and muscularis resulting in vasculopathy. By ten years of age, 44% of sickle cell patients demonstrate cerebral ischemia, infarction and atrophy (35% of these lesions are silent).
Cortical involvement in sickle cell disease demonstrates a variety of findings. Findings include evidence of acute or chronic infarcts in the cortical or deep white matter on T2 and FLAIR weighted images, particularly in a watershed distribution.
Typical findings on MR include hemorrhagic infarcts, punctate flow voids in the basal ganglia and an abnormal marrow signal with an expanded diploic space. Aneurysms in atypical locations, lack of vascular flow voids with prominent leptomeningeal and external carotid collaterals and stenosis of the distal internal carotid and proximal circle of Willis are typical vascular findings of sickle cell disease.
Differential diagnosis for the cerebrovascular findings of sickle cell disease include vasculitis of autoimmune and infectious etiologies. Substance abuse, particularly crack-cocaine, and radiation vasculitis can also produce similar findings. Connective tissue disorders such as Marfan and Ehlers-Danlos syndrome as well as homocystinuria can produce progressive arterial narrowing and occlusion. Thalassemia, another hemoglobinopathy, does not produce vascular findings but will result with a thickened skull with an expanded diploic space.