Neuroimaging in Cerebral Small Vessel Disease

The diagnosis of cerebral small vessel disease (SVD) is difficult because there is no consensus on clinical criteria and therefore, imaging is important for diagnosis. Most patients undergo brain imaging by computed tomography (CT), which is able to detect ischemic strokes, hemorrhages and brain atrophy and may also indicate white matter changes. Magnetic resonance imaging (MRI) remains the key neuroimaging modality and is preferred to CT in vascular cognitive impairment (VCI) because it has higher sensitivity and specificity for detecting pathological changes. These modalities for imaging morphology permit to detect vascular lesions traditionally attributed to VCI in subcortical areas of the brain, single infarction or lacunes in strategic areas (thalamus or angular gyrus), or large cortical-subcortical lesions reaching a critical threshold of tissue loss. In SVD multiple punctuate or confluent lesions can be seen in the white matter by MRI and were called leukoaraiosis. Another major neuroimaging finding of small vessel disease in VCI are microhemorrhages. However, while CT and MRI are able to detect morphologic lesions, these modalities cannot determine functional consequences of the underlying pathological changes. Positron emission tomography (PET) can support the clinical diagnosis by visualizing cerebral functions in typically affected brain regions. In SVD, Fluor-Deoxy-Glucose (FDG)-PET can clearly differentiate scattered areas of focal cortical and subcortical hypometabolism that differ from the typical metabolic pattern seen in Alzheimer Dementia (AD) with marked hypometabolism affecting the association areas. Additional PET tracers can further support the diagnosis of a type of dementia and also yield information on the underlying pathophysiology.