Glioma Brain Tumour

Classification
Gliomas are classified by cell type, by grade, and by location

By type of cell
Gliomas are named according to the specific type of cell they share histological features with, but not necessarily originate from. The main types of gliomas are:

• Ependymomas – ependymal cells.
• Astrocytomas – astrocytes (glioblastoma multiforme is the most common astrocytoma).
• Oligodendrogliomas – oligodendrocytes.
• Mixed gliomas, such as oligoastrocytomas, contain cells from different types of glia.

By grade
Gliomas are further categorized according to their grade, which is determined by pathologic evaluation of the tumor.

• Low-grade gliomas [WHO grade II] are well-differentiated (not anaplastic);these are not benign but still portend a better prognosis for the patient.
• High-grade [WHO grade III-IV] gliomas are undifferentiated or anaplastic; these are malignant and carry a worse prognosis.

Of numerous grading systems in use, the most common is the World Health Organization (WHO) grading system for astrocytoma, under which tumors are graded from I (least advanced disease – best prognosis) to IV (most advanced disease – worst prognosis).

By location
Gliomas can be classified according to whether they are above or below a membrane in the brain called the tentorium. The tentorium separates the cerebrum (above) from the cerebellum (below).

• supratentorial: above the tentorium, in the cerebrum, mostly found in adults (70%).
• infratentorial: below the tentorium, in the cerebellum, mostly found in children (70%).
• pontine: located in the pons of the brainstem. The brainstem has three parts (pons, midbrain and medulla); the pons controls critical functions such as breathing, making surgery on these extremely dangerous.

Signs and symptoms
Symptoms of gliomas depend on which part of the central nervous system is affected. A brain glioma can cause headaches, nausea and vomiting, seizures, and cranial nerve disorders as a result of increased intracranial pressure. A glioma of the optic nerve can cause visual loss.

Spinal cord gliomas can cause pain, weakness, or numbness in the extremities. Gliomas do not metastasize by the bloodstream, but they can spread via the cerebrospinal fluid and cause “drop metastases" to the spinal cord.

Causes
The exact causes of gliomas arenot known. Hereditary genetic disorders such as neurofibromatoses (type 1 and type 2) and tuberous sclerosis complex are known to predispose to their development. Gliomas have been correlated to the electromagnetic radiation from cellphones, and a link between the cancer and cell phone usage is considered plausible, though there is no conclusive evidence. Most glioblastomas are infected with cytomegalovirus, however the significance of this is not known. Pathophysiology High-grade gliomas are highly-vascular tumors and have a tendency to infiltrate. They have extensive areas of necrosis and hypoxia. Often tumor growth causes a breakdown of the blood-brain barrier in the vicinity of the tumor. Asa rule, high-grade gliomas almost always grow back even after complete surgical excision, and so are commonly called recurrent cancer of the brain.

Prognosis
Gliomas are rarely curable. The prognosis for patients with high-grade gliomas is generally poor, and is especially so for older patients. Of 10,000 Americans diagnosed each year with malignant gliomas, about half are alive 1 year after diagnosis, and 25% after two years. Those with anaplastic astrocytoma survive about three years. Glioblastoma multiforme has a worse prognosis with less than a 12-month average survival after diagnosis, though this has extended to 14 months with more recent treatments. For low-grade tumors, the prognosis is somewhat more optimistic. One study reported that low-grade oligodendroglioma patients have a median survival of 11.6 years another reported a median survival of 16.7 years.

Treatment
Treatment for brain gliomas depends on the location, the cell type and the grade of malignancy. Often, treatment is a combined approach, using surgery, radiation therapy, and chemotherapy. The radiation therapy is in the form of external beam radiation or the stereotactic approach using radiosurgery. Temozolomide is a chemotherapeutic drug that is able to cross the blood-brain barrier effectively and is currently being used in therapy for high-grade tumors.

Diagnosis
Diagnosing a glioma usually begins with a medical history review and exam by a brain disorder specialist (neurosurgeon), which includes checking your vision, hearing, balance, coordination and reflexes. Depending on those results, your doctor may request one or more of the tests Media channel under maintenance described below. All of your diagnostic testing can be completed in a few days rather than in several weeks or months.

Imaging tests
High-quality imaging and rapid test results are required. Radiologists who specialize in imaging the brain and nervous system perform and interpret each examination to the highest standard of quality. Imaging scans help gauge the tumour’s effect on your brain activity and function, and blood flow.

If a brain scan detects a tumour, especially multiple tumours, your doctor may test for cancer elsewhere in your body. Imaging tests may include:

• Computerized tomography(CT) scan. A CT scan uses a sophisticated X-ray machine linked to a computer to produce detailed, two-dimensional images of the brain. A CT scan can help identify certain types of tumors, especially those close to or involving bone.
• Magnetic resonanceimaging (MRI) scan. MRI uses a magnetic field and radio waves to create detailed images of the brain. Sometimes a special dye is injected into the bloodstream to make tumors appear different from healthy tissue (MR angiography). Perfusion, functional and intraoperative MRI scans may be done to identify blood flow and volume, critical brain areas involved in speech and motor activity, and the tumor’s precise location.
• Other brain scans. Other tests — such as magnetic resonance spectroscopy (MRS), single-photon emission computerized tomography (SPECT) or positron emission tomography (PET)scanning — help doctors gauge brain tumor activity and blood flow.
• Angiogram. A special dye is injected into the arteries that feed the brain, making the blood vessels visible on X-ray. This test helps locate blood vessels in and around a brain tumor.

Biopsy
Your surgeon will typically do a biopsy to diagnose a brain tumour and confirm its type. A biopsy involves removing a tiny piece of tumour tissue for examination under a microscope as part of the surgery to remove the tumour. The sample is examined instantly by a specialist in assessing brain tissue tumours (neuropathologist)to identify the kind of tumour, which is critical in determining the appropriate treatment for you. Studies show thatthe diagnosis may change substantially for at least one-fourth of people when an experienced neuropathologist does the analysis

Treatment
A neurosurgeon with expertise in brain cancers usually serves as the team lead.

Surgery
Neurosurgeons have significant expertise and experience in performing traditional and advanced glioma tumour removal surgeries.
When possible, you generally can be scheduled for surge.
Advances in neurosurgery offers the latest surgical options, technologies and techniques, including:

• Computer-assisted neurosurgery – Neuro Navigation
• Microscopic tumor removal surgery
• Awake brain surgery and functional brain mapping
• Intraoperative Imaging