Glioma brain tumors are derived from cells which constitute supporting tissue of the nervous system and constitute more than 50% of all neural tumors. They are divided pathologically into four grades. Grade IV gliomas are the most malignant. The most important of glioma encountered are Astrocytomas, glioblastomas, medulloblastomas and oligodendroglioma. These are infiltrative tumors and their common locations are cerebral hemisphere, cerebellum and brain stem.
Glioblastoma
It is an extremely malignant tumor which arises in late middle age. It may arise in patients with long standing seizure or personality disorders. A genetic or familiar incidence has also been incriminated.
Common sites are cerebral hemisphere, brain stem, cerebellum or spinal cord; it infiltrates the brain tissue extensively. Clinically patient presents with mental changes or seizures which predate the diagnosis from periods ranging from months to year. It is a highly vascular tumor. Patient may develop sudden neurologic defects following sudden hemorrhage or necrosis in the tumor mass.
CT scan reveals a heterogeneous pattern of tumor interspersed with hypo dense areas. MRI scan delineates a more extensive mass. The tumor is rapidly progressive and death results due to stupor or coma in 6-12 months.
Treatment is not satisfactory. It consists of chemotherapy and radiotherapy. Younger patients are known to improve in their quality and duration of life. Prognosis is poor and most patients do not survive for more than a year.
Astrocytomas
These are slow growing tumors and are relatively benign. They commonly arise from sub cortical white matter in adults. Other sites are cerebellum, Thalamus, Brain stem and optic nerves. These tumors are avascular and contain homogenous population of well differentiated astrocytes.
Astrocytomas are liable to undergo cystic changes. These are further divided into two groups – more benign one with survivor-ship of 5 years and infiltrative type who recur after surgery.
The tumor clinically evolves slowly spread over period of many years. Most of the symptoms are due to displacement of brain tissue or involvement of the nerve tracts (corticospinal, spinothalamic tracts, visual tracts). Hydrocephalus is rare. Astrocytomas in the cerebellar region cause ataxia and in coordination. Diagnosis is made by MRI since CT scan may be normal at early stage.
Degeneration in astrocytoma leads to rapid progression of symptoms and signs.
Treatment is by surgical excision of the growth. If the symptoms progress, radiation is recommended. Average survival after suigery is 5 years.
Medulloblastoma
It is a rapidly growing brain tumor which arises from the inferior portion of vermis of the cerebellum. It is mainly seen in children but young adults may be effected. It has a tendency to rapidly disseminate to ventricles, meninges and subarachnoid space. It is one of the more malignant forms of glioma.
Clinically, patient presents with headache in occipital region, vomiting and ataxia. Hydrocephalus and signs of brain stem compression appear later on.
Average duration of illness is about 6 months. Resection of the tumor followed by radiation to the posterior fossa, whole brain and spinal cord is employed. Chemotherapy role is doubtful. Metastases to distant organs may take place.
Oligodendroglioma
It is a slowly growing benign brain tumor relatively uncommon which primarily occurs in cerebral cortex or within the ventricles. It is seen in young adults in the third or fourth decades. Both benign and malignant forms are seen.
Diagnosis is made by CT scan which reveals a well defined mass with low attenuation and fine speckled calcium deposits and cysts. Malignant transformation of the tumor can be diagnosed if contrast enhanced CT is employed. Treatment is by resection, But despite being a benign growth results are not very good. Post operative chemotherapy and radiation is employed in some cases. Survival after surgery varies from 5 to 10 years.
Ependymoma
It is another brain tumor which arises from ependyma in the roof of the fourth ventricle. It is seen chiefly in young age. It may sometimes arise from the walls of other ventricles and the central canal of the spinal cord. Treatment is by resection and radiation.
Craniopharyngiama
It arises from the remnants of Rathke’s pouch (pituitary stalk). It is usually a brain tumor present in Suprasellar area and produces pressure effects like bitemporal heminopia leading on to total blindness and optic atrophy. It is a slow growing tumor and produces symptoms of neuroendocrine dysfunction.
Radiology of skull shows calcification in the growth, MRI confirms the diagnosis by a bright ‘T2’ signal.
