What are primary brain tumors?
A primary malignant brain tumor is one that originates in the brain itself. Although primary brain tumors often shed cancerous cells to other sites in the central nervous system (the brain or spine), they rarely spread to other parts of the body. Primary brain tumors are named due to the cell types, from which they are originated. Frequently encountered histologic brain tumor types are glioma, glioblastoma, astrocytoma, oligodendroglioma, medulloblastoma, meningioma and
neuroglioma. Tumors can be benign and are usually, but not necessarily, localized to a small area. They can also be malignant and invasive (i.e., spreading to neighbouring areas). Brain cells can be damaged by tumor cells by (i) directly being compressed from growth of the tumor, (ii) indirectly being affected from inflammation ongoing in and around the tumor mass, (iii) brain edema (swelling) or (iv) increased pressure in the skull (due to brain edema or to the blockage of the circulation of the cerebrospinal fluid).
Local tissue damage (either by direct or indirect mechanisms) causes focal neurologic symptoms, which vary due to the location of the brain tumor. Hemiparesis, aphasia, difficulty speaking, ataxia, hemihypoesthesia (numbness and decreased sensation of touch on one side of the body) and localized headache are some of the symptoms occurring due to the local effects of the brain tumor. Increased pressure in the skull or brain edema cause more generalized symptoms like generalized headache, nausea and vomiting, loss of consciousness (stupor or coma) and intellectual decline. Seizures due to the local irritating effect of the brain tumor or metabolic changes caused by the cancer are also frequently observed. Since the development of the skull is incomplete during infancy, infants with brain tumor may have increased head perimeter, bulging fontanelles or separated sutures.
Neurologic examination reveals local (specific to the location of the tumor) or generalized neurologic changes. Slowly progressive nature of the neurologic symptoms is suggestive of a possible brain tumor and the diagnosis is confirmed by CT scan or MRI of the head. Angiography, EEG examination or brain biopsy may aid in diagnosis in difficult cases. Although slow progression is an important hallmark of the disease, some brain tumors may enlarge very quickly and thus may cause sudden neurologic changes. Treatment includes the surgical removal of the tumor mass or the destruction of the tumor cells by radiation (radiotherapy) and/or drugs (chemotherapy) in cases with contraindications for a surgical operation.