Hypereosinophilic syndrome with central nervous system involvement: a case report

Cerebral infarction is the most common neurological complication in patients with hypereosinophilic syndromes (HES), typically occurring in border-zone regions. However, intracranial artery stenosis is rarely observed in HES, and the underlying mechanisms of cerebral infarction remain largely unknown. Here, we report a case of HES complicated by acute ischemic stroke secondary to severe stenosis of left middle cerebral artery (MCA). A diagnosis of idiopathic HES was established based on eosinophilia (14.08%) in bone marrow aspiration and negative genetic testing. Without contraindications, intravenous thrombolysis with alteplase was administered, resulting in a decrease of the National Institutes of Health Stroke Scale score from 13 to 2. High-resolution magnetic resonance imaging (HR-MRI) showed homogeneous, concentric wall thickening and enhancement in the terminal segments of the left internal carotid artery and at the origin of the MCA, indicating an inflammatory process. Follow-up HR-MRI at 17 months demonstrated a reduction in vessel wall enhancement after immunosuppressive therapy. Over the two-year follow-up period, the eosinophil count remained within the range of 0.22-1.09 × 10⁹/L, and no stroke recurrence was observed. In the literature review, only three cases of stroke associated with HES reported intracranial stenosis, all located in the M1 segment of the MCA. Their clinical outcomes improved following immunosuppressive therapy. Thus, intracranial large artery stenosis is a rare etiology of stroke in patients with HES. Homogeneous vessel wall enhancement on HR-MRI suggests an underlying vasculitis, which appears responsive to immunosuppressive therapy.