Childhood primary small vessel CNS vasculitis (SVcPACNS) is a very rare type of vasculitis that has high morbidity and mortality. Symptoms are nonspecific and because it affects the small blood vessels, but it is not possible to directly image the vessel wall. MRI findings cannot distinguish it from demyelinating conditions and other inflammatory brain diseases. Therefore, biopsy is required to confirm the diagnosis.
In a Canadian study (abstract #3179), Dr. Marinka Twilt et al used a standardized review instrument for assessing the pathology of brain biopsies and fancy statistical tests (called correspondence analysis) to determine whether there are histological features that can distinguish SVcPACNS from other inflammatory brain diseases. They compared 31 specimens with SVcPACNS, 11 with nonvasculitic inflammatory brain disease, and 12 epilepsy controls. Diagnoses were based on current classification criteria.
Using this innovative methodology, they identified several histological characteristics in SVcPACNS that differed significantly from controls and allowed for differentiation of these conditions. These factors included angiocentric or perivascular immune cell infiltrates (predominately T-cells), inflammation in both grey and white matter, and endothelial cell activation. Identifying these distinguishing features is important as treatment of SVcPACNS is different than that of inflammatory brain diseases.
Interestingly, the histological features for SVcPACNS for children are very different than what is seen in adult primary CNS vasculitis. In adults, granulomas and necrosis are reported whereas in children they are not seen. In addition, the T-cell infiltrates that are characteristic of SVcPACNS are rare in adults. Adult and childhood CNS vasculitis may be different diseases altogether. Alternatively, they may be different manifestations of the same disease altered in the adult with immune system maturation or environmental exposures.