[Intracranial cholesterol granulomas]

In the development of a cholesterol granuloma both cellular and vascular permeability factors have to be taken into consideration. It may arise as a special degradation product in a chronic cerebral infarct because of the partial insufficient activity of the macrophages. Consequently, the degradation of brain sphingolipids and other compounds does not follow the usual route of degradation and transportation by granular cells to the stage of neutral fat but the necrotic mass transforms into cholesterol esters. Cholesterol crystals produce an irritative effect to neighbouring tissues which may result in the formation of young fibroblasts with proliferative tendency in the vessel wall. Some of the fibroblasts take part in the proliferation of connective tissue, while the rest degenerate, producing more cholesterol or xanthomatous material. Inflammatory changes may also be associated with these lesions. The amount of cholesterol sometimes increases in the inner side of the thickening connective tissue layer. The final result may be an intracranial space occupying mass or it may end as a small cholesterol granuloma, as demonstrated in our incidental cases. By the time a granuloma has developed, the original vessel usually disappears completely, but sometimes remnants of vessels might prove the vascular origin. Other pathomechanisms should also be taken into consideration, such as a cholesterol embolus or anomalous vessel with a large cholesterol plaque in the wall. This also explains why trauma (hemorrhage, granulation), cholesterol embolus, inflammation, metabolic imbalance may predispose to the formation of a granuloma, as well as the hypercholesterolaemia. The nine cases demonstrate the significance of the intracranial granuloma from pathological, clinical and neurosurgical points of view. Such cases have not yet been reported in the national or international literature.