Regional Cerebral Blood Flow Patterns on ASL in Subacute Sclerosing Panencephalitis: Quantitative Analysis and
Sabha Ahmed1, Ankit Arora1, Anuran Mukherjee1
1From the Department of Neuroimaging and Interventional Radiology (S.A., A.A., S. R., C.M., J.S.), Neurology (A.M., L.G.V.), National Institute of Mental Health and Neurosciences (NIMHANS), Bengaluru, Karnataka, India and Department of Radiology (G.B.), Mayo Clinic, Rochester, Minnesota, USA.
Background And Purpose:
Subacute sclerosing panencephalitis (SSPE) is a progressive, uniformly fatal neuroinflammatory disease caused by persistent measles virus encephalitis, characterised by chronic T-cell-mediated inflammation, progressive demyelination, and cortico-striatal-thalamic network dysfunction. Conventional MRI characterises established structural disease but does not capture early haemodynamic alterations. We aimed to characterise regional perfusion patterns using cerebellar-normalised arterial spin labeling (ASL) ratios, define qualitative perfusion phenotypes, and examine their association with clinical severity and disease staging in a cohort of patients with confirmed SSPE.
Materials And Methods:
33 patients with confirmed SSPE (mean age 13.9 ± 6.7 years; 23 male) and 8 age-matched controls underwent 3T MRI including ASL in this retrospective case-control study. Cerebellar-normalised perfusion ratios (CNRs) were computed across 8 bilateral cortical and subcortical regions of interest. Group comparisons used Mann-Whitney U testing; Spearman correlations assessed the Neurological Disability Index (NDI), Barthel Index and illness duration. Jabbour stage comparisons used Kruskal-Wallis testing with post-hoc pairwise comparisons.
Results:
CNRs were significantly elevated in SSPE versus controls in 6/8 bilateral regions. The strongest discriminators were the lentiform nucleus, occipital cortex, and caudate nucleus. Basal ganglia hyperperfusion was the dominant ASL pattern (18/33, 54.5%), whereas structural basal ganglia abnormalities were present in only 5/33 patients (15.2%), demonstrating a marked perfusion-structure dissociation. A four-region composite achieved an AUC of 0.9 with 100% specificity. Deep grey matter CNRs correlated significantly with NDI across five subcortical regions but showed no correlation with illness duration.
Conclusions:
ASL-derived cerebellar-normalised perfusion ratios demonstrate regionally specific hyperperfusion in SSPE, likely reflecting the haemodynamic consequences of active neuroinflammation and cortico-striatal-thalamic network dysfunction. The marked dissociation between ASL-detected basal ganglia hyperperfusion and structural MRI signal change suggests that perfusion imaging may detect disease-related haemodynamic alterations before structural injury becomes radiologically evident. Correlation of deep grey matter CNRs with neurological severity, but not disease duration suggests that ASL may track the biological intensity of disease activity rather than its chronological extent. These findings warrant prospective validation in larger cohorts before CNRs can be recommended as routine biomarkers in SSPE.
