Structural connectivity mediates the relationship between blood oxygenation and cognitive function in sickle cell...

Area of Science:

• Neuroscience
• Hematology
• Medical Imaging

Background:

• The impact of reduced hemoglobin (Hb) and peripheral oxygen saturation on brain structure in sickle cell disease (SCD) is not fully understood.
• Silent cerebral infarcts are common in SCD, but their direct role in cognitive dysfunction is debated.
• Understanding the relationship between blood oxygenation, brain connectivity, and cognition is crucial for managing SCD.

Purpose of the Study:

• To investigate the effect of structural brain connectivity on cognitive function in sickle cell disease patients using graph-theoretical analysis.
• To examine the relationships between network properties, blood oxygenation (hemoglobin and oxygen saturation), and cognitive indices (working memory and processing speed).
• To determine whether cognitive impairment is mediated by hypoxic-ischemic effects on white matter or by silent cerebral infarcts.

Main Methods:

• Diffusion magnetic resonance imaging (dMRI) data from 92 sickle cell disease patients and 54 control subjects were analyzed using graph-theoretical network analysis.
• Relationships between network properties (edge density, efficiency) derived from streamline counts and fractional anisotropy were assessed against Hb levels, oxygen saturation, and cognitive scores.
• Multiple regression and path analyses were employed to elucidate direct and indirect effects of blood oxygenation and network properties on cognition.

Main Results:

• A specific brain subnetwork showed weakened connectivity in SCD patients compared to controls.
• Hemoglobin levels significantly affected overall network edge density, while peripheral oxygen saturation impacted subnetwork efficiency.
• Structural connectivity efficiency, particularly in a specific subnetwork, significantly influenced working memory and processing speed indices, with no significant effect from silent cerebral infarcts.

Conclusions:

• Cognitive impairment in sickle cell disease is primarily mediated by hypoxic-ischemic effects on normal-appearing white matter, rather than silent cerebral infarcts.
• Network-based methods using dMRI are valuable for identifying biomarkers of cognitive dysfunction in SCD patients.
• Reduced oxygen saturation indirectly affects processing speed through its impact on structural connectivity efficiency in specific brain subnetworks.