Przemyslaw Kosinski BS, Presenter: Nothing to Disclose

Jackie Leung, Abstract Co-Author: Nothing to Disclose

Manohar Meghraj Shroff MD, Abstract Co-Author: Nothing to Disclose

Suzan Williams, Abstract Co-Author: Nothing to Disclose

Gabrielle deVeber, Abstract Co-Author: Nothing to Disclose

Andrea Kassner PhD, Abstract Co-Author: Nothing to Disclose

The most devastating complication of sickle cell disease (SCD) is overt stroke, which occurs in more than 10% of children. Patients with cerebral blood flow velocities (CBFv) >200cm/s on Transcranial Doppler (TCD) are at highest risk of stroke. There are two models that explain how increased CBFv in SCD increases risk of stroke: the vasculopathy-stenosis and the hemodynamic insufficiency (HI) models. The stenosis model was originally used to attribute stroke onset to high CBFv. However, in the STOP trial, 79% of children with SCD had minor/no stenosis. This favours the HI model, which postulates that cerebral vessels have only a finite capacity to dilate, which is compromised in SCD due to chronic anemia. As a result it poises the cerebral vasculature for ischemia and subsequent stroke. The aim of the study was to investigate the HI model in children with SCD by quantifying the capacity of vasodilation using an MR- based cerebrovascular reactivity (CVR) defined as a change in cerebral blood flow (CBF) in response to a vasoactive stimulus. We hypothesize that CVR is reduced and correlates with the degree of anemia. 

30 SCD patients (10-18 years) were imaged on a clinical MRI system. A hypercapnic challenge (CO2) was administered in synchrony with a blood-oxygen-level dependent (BOLD) MRI to measure relative CBF changes. Anatomical images were also acquired and reviewed by a radiologist to exclude with significant stenosis, large white matter lesions or vascular abnormalities. CVR maps were generated by correlating the BOLD MRI signal change with the corresponding CO2 values. Mean CVR values were then calculated based on gray and white matter segmentation. Hct values were obtained from hematology records. Pearson correlation coefficients were calculated for CVR and hct as well as CVR and CBF. 

CVR demonstrated a moderately strong correlation with hct, r=0.68 (p=0.01). The correlation between CVR and gray matter CBF was moderately strong, r=-0.63 (p=0.021). 

Our results show that CVR is associated with the degree of anemia in children with SCD who do not have a stenosis. This seems to support the HI model of stroke risk in this population.

The degree of anemia needs to be considered when assessing stroke risk in SCD. CVR seems to be superior to TCD measures of high CBFv, as CVR can fully describe the status of the cerebral vasculature.

Kosinski, P, Leung, J, Shroff, M, Williams, S, deVeber, G, Kassner, A, Assessing the Hemodynamic Insufficiency Model of Stroke Risk in Children with Sickle Cell Disease Using MR-based Measures of Cerebrovascular Reactivity.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014544.html