Pattern and Severity of Leukoaraiosis and Microvascular Resistance- Inputs from a TCD Study from South Asia.

Background and Purpose: Leukoaraiosis is thought to be related to long-standing microvascular ischemia. The pathogenic mechanisms and hemodynamic changes could be different for periventricular and deep white matter leukoaraiosis. In this cross-sectional study, we examined whether the Pulsatility Index (PI) in Transcranial Doppler ultrasonography (TCD), which can give indirect information regarding downstream microvascular resistance and compliance, is different for leukoaraiosis in periventricular and deep locations. Correlation between presence of leukoaraiosis and PI was also studied since it was not studied in South-Asian patients before. Methods: Consecutive patients with suspected lacunar stroke or white-matter disease, undergoing MR brain imaging were included. Vascular imaging was done with CT or MR Angiography to rule out significant (>50%) stenosis. Fazeka's grading was done for severity of leukoaraiosis and mean PI in the middle cerebral artery (MCA) was obtained with trans-temporal TCD. Results: Ninety patients (Mean age 61 ± 10.9 years, 29% females) were available for final analysis. Age, hypertension, diabetes mellitus, CAD, and presence of leukoaraiosis were strongly associated with elevated mean PI in univariate analysis. In multivariate analysis, presence of leukoaraiosis was significantly associated with higher mean PI after adjusting for other variables. Mean PI strongly correlated with both periventricular (Spearman's correlation coefficient 0.56, P = 0.01) and deep white matter (Spearman's correlation coefficient 0.63, P = 0.01) leukoaraiosis. Conclusions: Our study confirms the correlation of Pulsatility Index with leukoaraiosis in South-Asian patients. Interestingly, changes in microvascular resistance appeared to be similar for both periventricular and deep white matter leukoaraiosis in spite of potential differences in etiopathogenesis.

The Imaging of Localization Related Symptomatic Epilepsies: The Value of Arterial Spin Labelling Based Magnetic Resonance Perfusion

Accurate identification of the epileptogenic zone is an important prerequisite in presurgical evaluation of refractory epilepsy since it affects seizure-free outcomes. Apart from structural magnetic resonance imaging (sMRI), delineation has been traditionally done with electroencephalography and nuclear imaging modalities. Arterial spin labelling (ASL) sequence is a non-contrast magnetic resonance perfusion technique capable of providing similar information. Similar to single-photon emission computed tomography, its utility in epilepsy is based on alterations in perfusion linked to seizure activity by neurovascular coupling. In this article, we discuss complementary value that ASL can provide in the evaluation and characterization of some basic substrates underlying epilepsy. We also discuss the role that ASL may play in sMRI negative epilepsy and acute scenarios such as status epilepticus.