Reduced ratio of afferent to total vascular density in mesial temporal sclerosis.

Mesial temporal sclerosis (MTS) is the most common cause of drug-resistant temporal lobe epilepsy in adults. Despite nearly 2 centuries since the first reports of MTS, relatively little is known about its etiology and pathogenesis. Increasing attention has been directed toward the potential role of vascular abnormalities in MTS. We evaluated the hippocampal microvasculature in 9 MTS cases and 3 non-MTS controls using celloidin tissue sections and markers for total (collagen type IV) and afferent (enzymatic alkaline phosphatase) vessels. Tissue sections were assessed by light microscopy and quantified by threshold analysis of digital images and stereological analysis using the Space Balls probe. Although consistent alterations in the total microvascular density were not found, there was a significant reduction in the density of afferent vessels using both methodologies; these reductions were in areas CA2 and CA3 by image threshold analysis and in area CA3 using stereological measures of the ratio of afferent to total vessels. Increased numbers of string vessels (i.e. remnants of regressing vasculature) were also observed in Ammon's horn, suggesting vascular degeneration in the MTS hippocampus. These findings may help further our understanding of the pathophysiology of MTS.