The brain capillaries in Alzheimer's disease
BALOYANNIS S.I., COSTA V., MAVROUDIS I., BALOYANNIS I.S.

In six brains derived from patients suffered from Alzheimer's disease, we attempted to proceed in morphological study of the capillaries, using silver impregnation technique, based on a modification of the rapid Golgi staining, associated with electron microscopy. Specimens have been selected from every area of the brain hemispheres, the hippocampus, the cerebellum, the thalamus, the lateral and medial geniculate bodies, the anterior and posterior colliculi and the locus coeruleus. The Golgi impregnation technique revealed an impressive poverty of the capillary network all over the brain cortex, particularly in the acoustic and optic cortices, the hippocampus the cerebellum, the thalamus and the brain stem. Most of the capillaries demonstrated local stenosos and dilatations, tortuosities, global and fusiform microaneurysms and abnormal capillary loops. The most marked alterations were seen in the hippocampus, the parietal cortex, the prerhinal cortex, the prefrontal cortex as well as the medial and lateral geniculate bodies. The capillaries of the cerebellar cortex and the dentate nucleus were less affected in comparison with those of the hippocampus and the parietal cortex. The most serious morphological alterations consisted of the local stenosis and the poststenotic dilatations as well as the formation of micro aneurysms in the places of the bifurcation of the capillary branches. The capillary density was decreased at any area of the cortex and the subcortical centers in comparison with the normal control brains of patients, who were neurologically unremarkable and have had the same age with those who suffered from Alzheimer's disease. The capillaries of the locus coeruleus demonstrated fusiform aneurysms and local stenosis and an impressive decline of the capillary density in comparison with the normal controls. Electron microscopy revealed disruption of the blood brain barrier associated with thickness of the basal membrane, astrocytic proliferation, marked thickness of the astrocytic perivascular processes (the astrocytic feet) and substantial microglial proliferation. We should have thought that both of the pathological components, namely the Alzheimer's changes and the alternation of the capillaries may result in the dramatic loss of the dendritic spines, which is also associated with mitochondrial alterations and the fragmentation of Golgi apparatus. The disruption of the blood brain barrier on the other hand reasonably exposes the neuropile space to many noxious factors, which may induce cellular necrosis at the cortical and the subcortical level. In conclusion the majority of the cases of cortical dementia, which may be diagnosed as Alzheimer's disease, according to the clinical and neuropsychological criteria, been assessed from the neuropathological point of view may be accepted as mixed type of dementia, associating the accumulation of the neuritic plaques in the neuropile space, the accumulation of the α-β peptide in the neurons and the axonic and dendritic profiles, the neurofibrillary tangles, the synaptic alterations and the loss of spinal density with the disruption of the blood brain barrier and the multiple morphological alterations of the brain capillaries. The capillary alterations in Alzheimer's disease may be considered that pleads in favor of the fact that many components may play an important role in plotting the pathogenetic background of the disease and lead reasonably to the concept that a multidimentional therapeutic regime, including vascular and haemodynamic support, might be beneficial. Encephalos 2008, 45(4):220-225.

Key words: Alzheimer's disease, brain capillaries, Golgi staining, electron microscopy, mixed dementia.