Glioma overview

# Overview
A glioma is a type of primary central nervous system (CNS) tumor that arises from glial cells.  The most common site of involvement of gliomas is the brain, but gliomas can also affect the spinal cord or any other part of the CNS, such as the optic nerve. Gliomas were reported as early as the 1850s. Retinal gliomas were most commonly reported because they were easier to detect and sample in the absence of advanced imaging and surgical techniques. Glioma may be classified into several subtypes based on the type of cell, grade, and location. The pathogenesis of cerebral glioma involves invasion of the tumor cells into the adjacent normal brain tissue. The gross and histopathological appearance of glioma varies with the tumor grade and type. Glioma must be differentiated from primary CNS lymphoma, cerebral metastases, meningioma, brain abscess, cavernous malformation, stroke, acute disseminated encephalomyelitis, cavernous sinus syndrome, intracranial hemorrhage, gerstmann syndrome, spinal tuberculosis, hamartoma, germinoma, teratoma, piloid gliosis, and progressive multifocal leukoencephalopathy. The incidence of glioma is estimated to be 4.9 cases per 100,000 individuals in the US. Patients of all age groups may develop glioma. Males are more commonly affected with glioma than females. It usually affects individuals of the caucasian race. African american, latin american, and asian individuals are less likely to develop glioma. Common risk factors in the development of glioma are occupational factors, environmental factors, genetic factors, and viruses. Common complications of glioma include brain herniation, coma, metastasis, and recurrence. The prognosis of glioma varies with the grade of tumor. The 1-year and 2-year survival rate of patients with malignant glioma is approximately 50% and 25%, respectively. Common symptoms of glioma include morning headaches, nausea and vomiting, seizures, drowsiness, changes in speech, difficulty in swallowing, vision changes, abnormal eye movements, changes in personality, memory loss, loss of balance, difficulty in walking, weakness in extremities, numbness in extremities, pain in extremities, and loss of appetite. The CT scan and MRI findings of glioma vary with the tumor grade and type. The predominant therapy for glioma is surgical resection. Adjunctive chemotherapy and radiation may be required.

# Historical Perspective
- Gliomas were reported as early as the 1850s.
- The first recorded reports of gliomas were given in British scientific reports, by Berns in 1800 and in 1804 by Abernety
- With the first comprehensive histomorphological description being given in 1865 by Rudolf Virchow.
- In 1926 Percival Bailey and Harvey Cushing gave the base for the modern classification of gliomas.
- Between 1934 and 1941 the most prolific researcher in glioma research was Hans-Joachim Scherer, who postulated some of the clinico-morphological aspects of Glioblastoma multiforme.
- Retinal gliomas were most commonly reported because they were easier to detect and sample in the absence of advanced imaging and surgical techniques.

# Classification
- The classification and grading of gliomas have evolved over time, beginning in 1926 with a system devised by Bailey and Cushing and later revised by Kernohan, Ringertz, and others.
- As of the 2016 edition of the WHO classification, gliomas are classified based not only on histopathologic appearance but also on well-established molecular parameters
- Glioma may be classified into several subtypes based on the type of cell (ependymoma, astrocytoma, oligodendroglioma, and mixed gliomas), grade (low-grade and high-grade gliomas), and location (infratentorial and supratentorial).
- Astrocytomas are glial cell tumors
Develop from connective tissue cells called astrocytes.
The most common primary intra-axial brain tumor, accounting for nearly half of all primary brain tumors.
They are most often found in the cerebrum (the large, outer part of the brain), but also in the cerebellum (located at the base of the brain).
Astrocytomas can develop in adults or in children.
Pilocytic astrocytomas are low-grade cerebellum gliomas commonly found in children. In adults, astrocytomas are more common in the cerebrum.
High-grade astrocytomas, called glioblastoma multiforme, are the most malignant of all brain tumors.
- Develop from connective tissue cells called astrocytes.
- The most common primary intra-axial brain tumor, accounting for nearly half of all primary brain tumors.
- They are most often found in the cerebrum (the large, outer part of the brain), but also in the cerebellum (located at the base of the brain).
- Astrocytomas can develop in adults or in children.
- Pilocytic astrocytomas are low-grade cerebellum gliomas commonly found in children. In adults, astrocytomas are more common in the cerebrum.
- High-grade astrocytomas, called glioblastoma multiforme, are the most malignant of all brain tumors.
- Brain stem gliomas
Also called diffuse infiltrating brainstem gliomas, or DIPGs, are rare tumors found in the brain stem.
Cannot be surgically removed because of their remote location, where they intertwine with normal brain tissue and affect the delicate and complex functions this area controls.
These tumors occur most often in school-age children
Responsible for the greatest number of childhood deaths from primary brain tumors.
- Also called diffuse infiltrating brainstem gliomas, or DIPGs, are rare tumors found in the brain stem.
- Cannot be surgically removed because of their remote location, where they intertwine with normal brain tissue and affect the delicate and complex functions this area controls.
- These tumors occur most often in school-age children
- Responsible for the greatest number of childhood deaths from primary brain tumors.

# Pathophysiology
The pathogenesis of cerebral glioma involves invasion of the tumor cells into the adjacent normal brain tissue. Although in certain areas the margin of the tumor may seem to be macroscopically well defined from the brain, there are always microscopic nests of tumor cells extending well out into the brain. Genes involved in the pathogenesis of glioma include ERCC1, ERCC2, XRCC1, MGMT, IDH1, IDH2, p53, EGFR, TSC1, TSC2, RB1, APC, hMLH1, hMSH2, PMS2, PTEN, NF1, and NF2. The gross and histopathological appearance of glioma varies with the tumor grade and type.

# Causes
There are no established causes for glioma.

# Differentiating brain tumors from other diseases
Glioma must be differentiated from primary CNS lymphoma, cerebral metastases, meningioma, brain abscess, cavernous malformation, stroke, acute disseminated encephalomyelitis, cavernous sinus syndrome, intracranial hemorrhage, gerstmann syndrome, spinal tuberculosis, hamartoma, germinoma, teratoma, piloid gliosis, and progressive multifocal leukoencephalopathy.

# Epidemiology and Demographics
Glioma is the most common primary intracranial tumor. The incidence of glioma is estimated to be 4.9 cases per 100,000 individuals in the US. Patients of all age groups may develop glioma. Males are more commonly affected with glioma than females. It usually affects individuals of the caucasian race. African american, latin american, and asian individuals are less likely to develop glioma.

# Risk factors
Common risk factors in the development of glioma are occupational factors, environmental factors, genetic factors, and viruses.

# Screening
There is insufficient evidence to recommend routine screening for glioma.

# Natural History, Complications and Prognosis
Common complications of glioma include brain herniation, coma, metastasis, and recurrence. The prognosis of glioma varies with the grade of tumor. The 1-year and 2-year survival rate of patients with malignant glioma is approximately 50% and 25%, respectively.

# Staging
There is no established system for the staging of glioma.

# History and Symptoms
Common symptoms of glioma include morning headaches, nausea and vomiting, seizures, drowsiness, changes in speech, difficulty in swallowing, vision changes, abnormal eye movements, changes in personality, memory loss, loss of balance, difficulty in walking, weakness in extremities, numbness in extremities, pain in extremities, and loss of appetite.

# Physical examination
Common physical examination findings of glioma include aphasia, vision loss, strabismus, memory loss, sensory loss, paresis, abnormal gait, ataxia, papilledema, and focal neurological deficits.

# Laboratory Findings
There are no diagnostic lab findings associated with glioma.

# X Ray
There are no x-ray findings associated with glioma.

# CT
Head CT scan may be diagnostic of glioma. The CT scan findings of glioma vary with the tumor grade and type.

# MRI
Brain MRI may be diagnostic of glioma. The MRI findings of glioma vary with the tumor grade and type.

# Ultrasound
There are no ultrasound findings associated with glioma.

# Other Imaging Findings
Other imaging studies for high-grade gliomas include PET scan, which demonstrates accumulation of -fluorodeoxyglucose (increased glucose metabolism).

# Other Diagnostic Studies
Other diagnostic studies for glioma include biopsy, which demonstrates astrocytes with or without atypia and mitoses, depending on the type of glioma.

# Medical Therapy
Treatment for glioma depends on the location and grade. The predominant therapy for glioma is surgical resection. Adjunctive chemotherapy and radiation may be required.

# Surgery
Surgery is the mainstay of treatment for glioma.