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Neuroradiology Case of the Week

Case 394

March 2009

Xiang Liu, MD, PhD, and PL Westesson, MD, PhD, DDS

Clinical Presentation: A previously healthy 31-year-old male presented with 2 weeks of fatigue, weakness and progressive ataxia. The patient denied shortness of breath, cough, recent travel, gastrointestinal or genitourinary symptoms, allergies or drug use. Laboratory test revealed white cell count of 39.8 THOU/μL with 49% eosinophils, absolute eosinophil count is 19.5 THOU/uL. The peripheral blood smear test confirmed leukocytosis and more than 50% of the white blood cells were eosinophils. There were some hypersegmented neutrophils and rare bands, but there were no blast cells. Both RBC and platelet morphology were within normal limits. The platelet count was slightly elevated. The results of bone marrow biopsy showed mature eosinophils, but no neoplastic cells, and it was thought less likely that this process was related to an underlying neoplasm.

Imaging Findings: Echocardiogram and chest CT were performed, pulmonary and cardiac findings were normal. The first brain MR, which was 2 weeks after onset, revealed multiple small lesions located within the watershed regions of the bilateral cerebral hemispheres, within the bilateral cerebellum and bilateral basal ganglia. These lesions were with high signal on the T2-weighted and FLAIR images. Most of these lesions demonstrated restricted diffusion. Many of these lesions enhanced on the post-contrast T1-weighted images. Repeated MR after one week showed that the number and size of enhanced lesions decreased, but there were more lesions in the bilateral periventricular and subcortical white matter with restricted diffusion.

Diagnosis: Hypereosinophilic syndrome

Discussion: Hypereosinophilic syndrome(HES) characterized by an eosinophil count of more than 1500/μL for more than 6 months and multiorgan involvement without other causes of eosinophilia and in the absence of eosinophil blast cells in the marrow or blood. Three subtypes include myeloproliferative, lymphocytic, and idiopathic. There are 65% of HES patients with neurologic involvement, including three major types: peripheral polyneuropathy, encephalopathy, and central nervous system (CNS) thromboemboli infarction.
     The locations of the infarctions distributed particularly in the border zone or distal fields of the major cerebral arteries.
     Specific mechanism of hypereosinophilia-induced brain infarctions remains unclear. For the patients with cardiac involvement, microembolic to the CNS may be secondary to intracardiac thrombus formation due to endomyocardial fibrosis and thrombus formation by eosinophilic infiltration.
     However, small and multiple infarcts in the border zone thromboemboli may also occur in HES patients without demonstrable cardiac disease. It has been postulated in these cases, that local thrombus formation from a hyperviscous, hypercoaguable state or distant microthromboemboli within the vessels of the CNS may be the underlying mechanisms. Our case is featured as acute, extensive watershed infarctions with restricted diffusion by hypereosinophilia without evident cardiac abnormality.

References:

1. McMillan HJ, Johnston DL, Doja A. Watershed infarction due to acute hypereosinophilia. Neurology. 2008 Jan 1;70(1):80-2. [PubMed]
2. Kwon SU, Kim JC, Kim JS. Sequential magnetic resonance imaging findings in hypereosinophilia-induced encephalopathy. J Neurol. 2001 Apr;248(4):279-84. [PubMed]
3. Sarazin M, Caumes E, Cohen A, Amarenco P. Multiple microembolic borderzone brain infarctions and endomyocardial fibrosis in idiopathic hypereosinophilic syndrome and in Schistosoma mansoni infestation. J Neurol Neurosurg Psychiatry. 2004 Feb;75(2):305-7. [PubMed]
4. Battineni ML, Galetta SL, Oh J, Lango M, Brooks JJ, Schuster SJ, Loevner LA. Idiopathic hypereosinophilic syndrome with skull base involvement. AJNR Am J Neuroradiol. 2007 May;28(5):971-3. [PubMed]