To identify those factors associated with cerebral hemorrhage among brains with cerebral amyloid angiopathy (CAA), we undertook a comparative postmortem histopathological study of amyloid-containing vessels in the brains of patients with and without hemorrhage. Those without hemorrhage were represented by the following two groups: (1) elderly patients from a large general hospital (n = 66; age range, 75-107 years) and (2) patients with various neuropsychiatric disorders (n = 70; age range, 27-96 years). CAA was found in 45% of the first group and in 54% of the second group. The findings in these patients were compared with those in 17 brains in which both CAA and cerebral hemorrhage were present. We found that CAA was more severe in the brains with cerebral hemorrhage than in those without, and that fibrinoid necrosis was seen only in the brains with cerebral hemorrhage (12 of the 17 brains). Microaneurysms occurred only in the presence of severe, rather than moderate or mild, CAA. Serial sections in 2 brains of patients with cerebral hemorrhage showed fibrinoid necrosis, microaneurysms, and vascular rupture in close association with the hemorrhage. In 2 patients, hemorrhage was precipitated by trauma, and in 1, it was secondary to metastatic carcinoma. The features of brains from patients with CAA that are most consistently related to cerebral hemorrhage are (1) a severe degree of CAA and (2) the presence of fibrinoid necrosis, with or without microaneurysms.

A distinct subpopulation of striatal aspiny neurons, containing the enzyme nicotinamide adenine dinucleotide phosphate diaphorase, is preserved in the caudate nucleus in Huntington's disease. Biochemical assays confirmed a significant increase in the activity of this enzyme in both the caudate nucleus and putamen in postmortem brain tissue from patients with this disease. The resistance of these neurons suggests that the gene defect in Huntington's disease may be modifiable by the local biochemical environment. This finding may provide insight into the nature of the genetically programmed cell death that is a characteristic of the disease.

Dysmorphic alterations of dendritic arbors and spines in spiny striatal neurons were identified in section-Golgi impregnations of moderate and severe grades of Huntington's disease (HD). These alterations could be characterized as either proliferative or degenerative changes. Proliferative changes included prominent recurving of distal dendritic segments, short-segment branching along dendrites, and increased numbers and size of dendritic spines. Degenerative alterations consisted of truncated dendritic arborizations, occasional focal dendritic swellings, and marked spine loss. Proliferative changes were found primarily in moderate grades of HD, while degenerative changes were predominantly found in severe grades. Cytopathologic changes increased with neuropathologic severity. Similar morphologic alterations were observed in calbindin D28k (Calb) stained neurons in HD striatum. The immunoreactive intensity of Calb staining was increased in the distal dendrites of positive neurons in HD striatum. The present findings provide morphologic and quantitative evidence that confirms an early and marked involvement of spiny striatal neurons in HD and suggest that neuronal growth, rather than degeneration, may be the harbinger of cell death in this disorder.