Brain Neoplasms
Brain Neoplasms Definition
Brain neoplasms are tumors of the intracranial components of the central nervous system, including the cerebral hemispheres, hypothalamus, basal ganglia, thalamus, brain stem, and cerebellum. Brain neoplasms are further divided into primary (originating from brain tissue) and secondary (i.e., metastatic) forms. Primary neoplasms are categorized into benign and malignant forms. Generally, brain tumors may also be classified by age of onset, histologic type, or presenting location in the brain.
Brain Neoplasms Historical Background
Presenting complaints of patients with an intracranial neoplasm tend to be the same for primary brain tumors and intracranial metastases. Manifestations of the disease depend on the cause of the symptoms: an increase in ICP, shifting of intracranial contents, direct compression of essential gray or white matter, or secondary cerebral ischemia.
Brain Neoplasms Pathophysiology
Tumors of the brain produce neurologic manifestations through several of mechanisms. Small, strategically located tumors may cause damage to the vital neurologic pathways traversing the brain. Tumors can invade, infiltrate, and supplant normal parenchymal tissue, wreaking havoc on normal function. Because the brain is found in the relatively restricted repository of the cranial vault, growth of intracranial tumors with accompanying edema compresses some normal tissue. Tumors proximal to the third and fourth ventricles may hinder the flow of cerebrospinal fluid, leading to hydrocephalus. In addition, tumors generate new blood vessels (ie, angiogenesis), leading to the disruption of the normal blood-brain barrier and promoting edema. The cumulative effects of tumor invasion, hydrocephalus, and peritumor edema may elevate the intracranial pressure (ICP) and impair cerebral perfusion. Intracranial compartmental rise in ICP may ignite shifting or herniation of tissue under the falx cerebri, through the tentorium cerebelli, or through the foramen magnum. Slow-growing tumors, particularly tumors growing in the so-called silent areas of the brain, such as the frontal lobe, may be associated with a more insidious course. These tumors tend to be larger when detected.
Brain Neoplasms Prevalence
An approximation of the annual incidence rate of primary brain tumors range from 7-19.1 cases per 100,000. Metastatic tumors to the brain are more commonly found with more than 100,000 patients per year in the United States dying with symptomatic intracranial metastases. A rise in the prevalence of HIV infection corresponds to an increase in the occurrence of primary CNS lymphoma. Pituitary adenomas are exceptionally common, and they are common incidental findings on autopsy. Autopsy series of patients with systemic cancer show that intracranial metastases can be found in 18-24% of patients. The international incidence is not known, but it is thought to mirror that of the United States.