The insula of Reil constitutes a functionally intriguing complex of the brain related to multifunctional activities. We examined the subinsular region in 119 consecutively autopsied patients, as T2 hyperintense lesions are frequently observed in magnetic resonance diagnosis of this region. The patients were admitted in neurology wards and were diagnosed as having cerebrovascular disease in 55 patients (46%), other neurological diseases in 57 patients (48%) and non-neurological diseases in seven patients (6%). Demyelination of the white matter was semi-quantified as a fiber density score (percent stained area/total area) with computer-assisted image analysis on Klüver–Barrera-stained sections. Astrogliosis was assessed by immunohistochemistry for glial fibrillary acidic protein.
The lesion analysis showed a dilated perivascular space in 29 patients (24%), demyelination (fiber density score less than the mean − 1 SD) in 27 patients (23%), slit-shaped lesion in six patients (5%), lacunar infarction in one patient (1%) and cerebral hemorrhage in one patient (1%). A histologic–radiologic comparison in two patients with subcortical ischemic vascular dementia showed correspondence between subinsular hyperintensities, and demyelination, gliosis and a dilated perivascular space. These results indicate that subinsular lesions rarely signifies focal vascular lesions, and are consisted of demyelination, gliosis and a dilated perivascular space.