MR imaging and angiography of primary CNS vasculitis of childhood

Abstract

Background and purpose: Primary angiitis of the central nervous system of childhood (cPACNS) is a rare and ill-defined disease. In the absence of a brain biopsy, the diagnosis is based on typical clinical and imaging abnormalities. The aim of this study was to analyze systematically the MR imaging and MR angiographic (MRA) abnormalities in a large cohort of children with cPACNS.

Methods: We analyzed the MR imaging features of a single pediatric center cohort of 45 cPACNS patients. MR imaging studies were performed for all patients, and both MR imaging and MRA were performed for 42 patients, who formed the cohort for review of the presence and correlation of lesions. Proportions were calculated by using the Fisher exact test, and agreement between MR imaging and MRA was calculated by using the McNemar test. The sensitivity of each diagnostic technique was established.

Results: The most-common pattern of parenchymal abnormality was multifocal, unilateral involvement, each in 42/45 patients (93%). The lateral lenticulostriate artery terrritory was affected in 56% of cases, with involvement of a supratentorial deep gray matter structure in 91%. No infratentorial lesion occurred in the absence of supratentorial abnormality. MRA was normal in 12/42 patients (28.6%). Among the abnormal studies, stenosis was detected on MRA in 83% and was "benign" in appearance in 73% of patients and "aggressive" in 16.7%. Involvement was proximal in 83% and distal in 27% of patients. Multiple ipsilateral lesions were seen in 63%. MR imaging was abnormal in every patient where MRA was abnormal. With the assumption of MR imaging as the gold standard, the sensitivity of MRA was 72%. The agreement between MR imaging and MRA for abnormality was significant (P = .04).

Conclusion: We have illustrated the MR imaging and MRA appearances of cPACNS in the largest cohort to date. Both parenchymal and vascular lesions were predominantly proximal, unilateral, and multifocal within the anterior circulation. There was good agreement between MR imaging and MRA for lesion location. MR imaging findings were abnormal in all cases at diagnosis, and this remains the most sensitive technique to the detection of vasculitis.

Fig 1.

FLAIR (A) and isotropic (B) DWI MR images. Normal FLAIR imaging in the context of a 1-day history of right-sided weakness. DWI reveals restriction within the putamen and external capsule (white arrow).

Fig 2.

T2-weighted (A), FLAIR (B), and isotropic DWI (C) of a unilateral lesion in a patient with an acute or chronic presentation of worsening right-sided weakness. There are 2 T2-weighted hyperintense lesions involving the genu and posterior limb of the internal capsule (white arrow) and posterolateral putamen (black arrow). Both T2-weighted (A) and FLAIR (B) images reveal lesions of differing age with an anteromedial well-defined encephalomalacic cavity and a posterolateral lesion. The isotropic image (C) confirms a new focal area of infarction within the lateral lenticulostriate artery territory (black arrow) as an area of reduced diffusion.

Fig 3.

Fat-saturated T2-weighted MR imaging of bilateral lesions. There is T2-weighted signal intensity abnormality involving bilateral basal ganglia nuclei, thalami, subcortical, and deep white matter, greater on the right. The distribution of abnormality is consistent with both anterior and posterior circulation involvement.

Fig 4.

T2-weighted MR imaging. There is expansion and irregular hyperintensity within the right middle cerebellar peduncle extending into the right cerebellar deep white matter and dentate nuclei. Mild fourth ventricular effacement is evident (black arrow). The appearances are consistent with anterior inferior cerebellar artery (AICA) and perforator infarcts.

Fig 5.

A, FLAIR demonstrating acute infarct within a superficial distribution. There is cortical swelling and hyperintensity and adjacent patchy subcortical involvement within the right MCA territory. Additional punctate signal intensity abnormalities are present within the right external capsule and parietal deep white matter (black arrows). B, T2-weighted axial MR imaging demonstrating bilateral peripheral infarcts with hyperintensity within deep and subcortical white matter best appreciated within the right frontal lobe. Bilateral cortical involvement and left deep white matter involvement are appreciated more easily on FLAIR (not shown).

Fig 6.

Time-of-flight MRA maximum intensity projection (MIP) viewed from posteriorly. The posterior circulation has been removed. There is smooth, regular, concentric, distal left internal carotid and proximal prebifurcation M1 segment flow attenuation (white arrowhead) resulting in reduction in flow signal intensity from remaining MCA branches (white arrow). The A1 segment of the ACA is unaffected. The pattern of proximal involvement was seen in >80% and the “benign” morphology was seen in half of patients studied.

Fig 7.

Time-of flight MIP oblique view demonstrating distal involvement of the postbifurcation M1 and proximal M2 segments. There is eccentric, irregular narrowing with alternating stenosis and dilation consistent with beading (white arrowheads). “Aggressive” features are said to be the hallmark of vasculitis but were seen in only 11% of our patients. Multiple additional stenoses are present within the left M2 and P2.

Fig 8.

T2-weighted (A) and FLAIR (B) MR imaging demonstrating focal hyperintensity within the cortex of the postcentral gyrus (white arrow). There is widening of the adjacent sulci providing further clues to previous infarction here but the signal intensity abnormality may be overlooked owing to the adjacent CSF hyperintensity. A small subtle lesion is present within the ipsilateral posterior frontal lobe cortex (black arrowhead). Both the lesions are readily visualized on FLAIR imaging (B).