The main cause of spontaneous ICH is hypertensive vasculopathy. Other causes of non-traumatic ICH include: cerebral amyloid angiopathy, brain tumors, hemorrhagic infarctions, bleeding disorders, venous thrombosis, bleeding diathesis. A rare (2-5% range), but important etiology of ICH is intracranial neoplasm, which in some cases can be covered by the bleed.

Hemorrhagic intracranial tumors can be primary or secondary, the most common being: glioblastoma, pilocytic astrocytoma, oligodendroglioma, pituitary adenoma, ependymoma, hemagiopericytoma, central neurocytoma, respectively metastases from melanoma, renal cell, thyroid or lung carcinoma.

When looking at a CT or MRI scan of the brain firstly, it is important to differentiate between cytotoxic and vasogenic edema.

Cytotoxic edema is caused by the death of the cells, the sodium-potasium pump stops working, therefore, the fluid leaks into the cells and cause the swelling. The grey and the white matter are affected, consequently the imagining sign is the loss of grey-white matter differentiation. In this type of cerebral edema, the blood-brain barrier (BBB) remains intact. The main cause of cytotoxic edema is brain infarction, other causes can be hypotoxic injury and HSV encephalitis.

On the other hand, vasogenic edema appears when a process destroys the BBB, then the fluid leaks out, predominantly in the white matter, the cortical density is preserved. A damaged BBB allows even the contrast to leak-out, therefore, the rule is: Give contrast when you see a vasogenic edema! because usually there is an enhancing lesion underneath (tumor, metastases or abscess).

The intracranial bleeding can be divided into two subtypes: intraaxial and extraaxial. Intraaxial hemorrhage is caused by hypertension, amyloid angiopathy, vascular malformation, venous thrombosis, intracerebral tumor, hemorrhagic transformation of an infract, trauma. An intraaxial bleeding determined by the hypertension, usually occurs in the deep structures of the brain, being central in location.

In elderly patients, the principal cause of ICH is amyloid angiopathy, the imaging sings are: lobar hemorrhage with a volume that is larger than the associated edema on CT scan, and when the MRI scan is performed lots of other microhemorrhages are spotted, peripherally in the brain.

In younger patients, lobar hemorrhage also associated with not so much edema, but where the subarachnoid hemorrhage, bleeding in the ventricles and other signs are present, a CT angiogram is mandatory to look for a vascular malformation (AVM).

A lobar hemorrhage with too much vasogenic edema around it, is a sign to give contrast, because there can be an underlying cause which is coverd by the bleeding. The form of the bleed is also important, if it is regular in shape, round for exemple, has a large vasogenic edema around it, the first thought should be hemorrhage into a brain metastases.

The physiopathology of intratumoral bleeding in unclear, but it includes rupture of tumor vessels, tumor necrosis and invasion of the tumor in the parenchymal vessels. The blood supply of the brain malignant tumor is represented by the tumor-generated blood vessels, which are immature and more permeable than the normal blood vessels of the brain, without BBB. High-grade tumors, especially glioblastomas produce a vascular endothelial growth factor (VEGF), an important mediator of angiogenesis, which generates the formation of neovessels. Experimental studies demonstrated that some types of VEGF are more susceptible to produce intratumoral bleeding than others. Therefore, the risk of the hemorrhage is directly proportional with the grade of the tumor.

There are three patterns of capillary growth into the brain tumors: axial, glomeruloid and retiform; the last one is associated the most with important neoplasm bleeding. Retiform type of capillary growth is significantly present in oligodendorgliomas, a low-grade tumor, but owing the fact that this kind of neoplasms are rare, oligodendrogliomas rate only for o small percent of tumor-related hemorrhages. In other primary brain neoplasms, the predisposition of tumor hemorrhage is poorly defined and is not associated with a particular histological subtype.

Brain metastases from any kind of tumor can cause bleeding, but the tendency of intratumoral hemorrhage is different, depending on the neoangiogenesis mechanism which is similar to the primary tumor. In melanomas, thyroid and renal cell carcinomas, the malignant cells invade and damage the tumor blood vessels, which usually leads to hemorrhage. Some studies show that renal cell carcinoma brain metastases are the most likely to cause bleeding, but due to the fact that lung cancer has a high incidence and tendency to metastasize to the brain, brain metastases from bronchogenic carcinoma remain the most common cause of metastatic ICH.