Acute Ischemic Stroke in a 4-Year-Old with Hemoglobin SS Disease Despite a Normal Recent Transcranial Doppler
Muhammad Waleed Butt, Angelica GarzonAbstract
Background
Stroke is a major complication of sickle cell disease (SCD), historically affecting up to 11 % of children with HbSS by age 20 in the absence of screening. Introduction of annual transcranial Doppler (TCD) ultrasonography between ages 2-16 years has reduced the incidence of first stroke to ≈1 %. Chronic transfusion therapy is recommended for children with abnormal TCD velocities ≥ 200 cm/s. Nevertheless, ischemic stroke can occur despite a recent normal TCD, particularly in the setting of evolving large-vessel or Moyamoya-type vasculopathy.
Methods
A 4-year-old boy with HbSS presented with acute left-sided weakness and limp approximately 20 hours after onset. His TCD one month earlier showed normal velocities. Initial CT, CTA, and perfusion studies were unremarkable, but MRI revealed acute right-sided watershed infarction and chronic left-sided gliosis. MRA and cerebral angiography demonstrated chronic right internal carotid artery (ICA) occlusion with robust collateral flow, consistent with likely sickle cell-associated Moyamoya vasculopathy. Emergent exchange transfusion reduced HbS from 76 % to 13 %. No endovascular intervention was required. He was transitioned to a chronic transfusion program and discharged with outpatient physical therapy.
Results
Cerebrovascular accidents are among the most devastating complications of SCD. Before systematic screening, approximately 11 % of children with HbSS experienced overt stroke by age 20; after adoption of the STOP protocol, the rate fell to about 1 %. Strokes are usually ischemic, caused by progressive stenosis of the distal ICA or MCA, with or without Moyamoya collaterals. Despite routine TCDs, events can occur when pathology lies proximal to the insonation window or when collateral circulation masks elevated velocities. Moyamoya describes progressive stenosis or occlusion of the terminal ICA and proximal MCA/ACA with compensatory collaterals; when secondary to SCD, it is termed Moyamoya syndrome, seen in up to 20 % of affected children. Although TCD screening has reduced stroke incidence, it assesses only intracranial MCA and distal ICA flow and cannot detect proximal ICA disease or collateral networks. A normal TCD does not exclude cerebrovascular disease; new neurological symptoms warrant urgent MRI/MRA. Management requires immediate exchange transfusion targeting Hb ≈ 10 g/dL and HbS < 30 %, chronic transfusions every 3 to 4 weeks, and consideration of EDAS for refractory cases.
Conclusions
This case demonstrates that ischemic stroke may occur in HbSS children even after a recent normal TCD, owing to subclinical or proximal large-vessel disease such as Moyamoya vasculopathy. Clinicians should maintain a high index of suspicion: any new neurologic deficit warrants urgent MRI/MRA and prompt exchange transfusion, irrespective of prior screening results. Integration of TCD with periodic MRI/MRA surveillance, coordinated hematology-neurology care, and timely consideration of surgical revascularization are critical to prevent recurrence and optimize neurodevelopmental outcomes.