Neurologic dysfunction may result from the following:
Invasion and destruction of brain tissue by the tumor
Direct compression of adjacent tissue by the tumor
Increased intracranial pressure (because the tumor occupies space within the skull)
Bleeding within or outside the tumor
Cerebral edema
Obstruction of dural venous sinuses (especially by bone or extradural metastatic tumors)
Obstruction of CSF drainage (occurring early with 3rd-ventricle or posterior fossa tumors)
Obstruction of CSF absorption (eg, when leukemia or carcinoma involves the meninges)
Obstruction of arterial flow
Rarely, paraneoplastic syndromes (see Paraneoplastic Syndromes)
A malignant tumor can develop new internal blood vessels, which can bleed or become occluded, resulting in necrosis and neurologic dysfunction that mimics stroke.
Benign tumors grow slowly. They may become quite large before causing symptoms, partly because often there is no cerebral edema. Malignant primary tumors grow rapidly but rarely spread beyond the CNS. Death results from local tumor growth and thus can result from benign as well as malignant tumors. Therefore, distinguishing between benign and malignant is prognostically less important for brain tumors than for other tumors.
Symptoms and Signs
Symptoms caused by primary tumors and metastatic tumors are the same. Many symptoms result from increased intracranial pressure:
Headache
Deterioration in mental status
Focal brain dysfunction