What is the centrum semiovale?

Centrum Semiovale: Anatomical Definition and Clinical Significance

What is the Centrum Semiovale?

The centrum semiovale is a specific region of subcortical white matter located deep within the cerebral hemispheres, positioned superior to the lateral ventricles and beneath the cortical gray matter. This anatomical area consists primarily of white matter fiber tracts and represents a critical zone for both neuroimaging interpretation and understanding cerebrovascular pathology 1.

Anatomical Location and Characteristics

The centrum semiovale occupies the deep white matter territory at the level where the cerebral hemispheres are widest, essentially forming the white matter core above the lateral ventricles. This region is:

• Positioned in the same axial plane as cortical target regions, making it less susceptible to differences in scatter correction between superior and inferior brain planes 2
• Supplied by superficial penetrating arteries (medullary arteries) that arise from cortical branches of the middle cerebral artery 3
• Corresponds to the cortical border-zone territory, distinguishing it from the corona radiata which represents the internal border-zone 3

Clinical Relevance in Neuroimaging

Reference Region for PET Imaging

The centrum semiovale serves as a reference region in amyloid PET imaging due to its lack of amyloid accumulation in subcortical white matter 2. However, this application has important caveats:

• Technical advantages: Being in the same plane as cortical regions reduces technical variability
• Limitations: Region delineation has not been standardized, and cortical signal can spillover into adjacent white matter 2
• For SV2A PET imaging: The centrum semiovale shows negligible concentrations of synaptic markers, though some degree of specific binding has been observed 4

Marker of Cerebral Amyloid Angiopathy (CAA)

Severe perivascular spaces in the centrum semiovale (CSO-PVS) represent a critical diagnostic marker for CAA in the Boston Criteria 2.0 5. Specifically:

• Diagnostic threshold: >20 visible perivascular spaces in one hemisphere on T2-weighted sequences 5
• Pathophysiological significance: Enlarged CSO-PVS correlate with lower CSF Aβ40 levels, suggesting they serve as a noninvasive marker of vascular amyloid deposition 6
• Clinical utility: Combined with one hemorrhagic marker, severe CSO-PVS can establish probable CAA diagnosis even without multiple hemorrhagic lesions 5

Cerebrovascular Disease Patterns

The centrum semiovale demonstrates distinct vulnerability patterns in different vascular pathologies:

• Internal carotid artery disease: The centrum semiovale is highly susceptible (72.7% of cases), more so than basal ganglia or corona radiata 7
• Middle cerebral artery disease: Rarely produces centrum semiovale infarcts, instead affecting striatocapsular and corona radiata regions 7
• Embolic mechanisms: Approximately half of centrum semiovale infarcts result from embolic occlusion of medullary arteries 3

Neuropathological Sampling

In research and autopsy protocols, the centrum semiovale serves as a standard sampling site. The CERAD protocol specifically recommends including anterior centrum semiovale blocks when assessing cerebrovascular disease and vascular cognitive impairment 1. This standardization allows for:

• Consistent assessment of white matter pathology
• Evaluation of small vessel disease burden
• Correlation with neuroimaging findings

Key Clinical Pitfalls

When interpreting centrum semiovale findings:

• Do not confuse with corona radiata: These are distinct anatomical regions with different vascular territories and clinical implications 3
• Perivascular space assessment requires proper sequences: T2-weighted imaging is essential for accurate CSO-PVS quantification 5
• Context matters for infarcts: Location in centrum semiovale versus corona radiata suggests different underlying vascular pathologies (ICA versus MCA disease) 7
• Avoid overcounting in reference region applications: Proper ROI definition is critical to minimize gray matter spillover when using centrum semiovale as a reference 2, 4