Brain tumor overview

# Overview
Primary brain tumors include any tumor that starts in the brain. Primary brain tumors can start from brain cells, meninges, nerves, or glands. Brain tumors can be classified into two main categories: primary and secondary tumors. Primary tumors originate in astrocytes, oligodendrocytes and ependymal cells. Secondary tumors originate in malignant cancers located primarily in other organs. The cause of brain tumors is unknown. These cancers should be differentiated from essential tremor, stroke, chronic subdural hematoma, meningitis, orbital optic neuritis, arteriovenous malformations and brain abscesses. Radiation is one the common risk factors for brain tumors. The complications of brain tumors are brain herniation, loss of brain function and recurrence. The most common symptoms of brain tumors are headache, seizures, visual changes and changes in personality, mood and concentration. On head CT scan, brain cancer is characterized by hypodense mass lesions. On MRI brain, brain tumor is characterized by hypointense or isointense on T1-weighted scans, or hyperintense on T2-weighted MRI. The predominant therapy for brain tumor is surgical resection. Meningiomas, with the exception of some tumors located at the skull base, can be successfully removed surgically. In more difficult cases, stereotactic radiosurgery, such as Gamma Knife radiosurgery remains a viable option. Most pituitary adenomas can be removed surgically using a minimally invasive approach through the nasal cavity and skull base (trans-nasal, trans-sphenoidal approach). Larger pituitary adenomas require a craniotomy (opening of the skull) for their removal. Radiotherapy, including stereotactic approaches, is reserved for inoperable cases. Adjunctive chemotherapy and radiation may be required.

# Historical Perspective

# Classification
Brain tumors can be classified into two main categories: primary and secondary tumors. Primary tumors originate in astrocytes, oligodendrocytes and ependymal cells. Secondary tumors originate in malignant cancers located primarily in other organs. Brain tumors are classified depending on location of the tumor, type of tissue involved and whether they are benign or malignant.

# Pathophysiology

# Causes
The cause of brain tumors is unknown.

# Differentiating brain tumors from other diseases
Brain tumors should be differentiated from essential tremor, stroke, chronic subdural hematoma, meningitis, orbital optic neuritis, arteriovenous malformation, intraocular optic neuritis and brain abscess.

# Epidemiology and Demographics
In 2012, the prevalence and incidence of brain tumors were 148,818 and 6.4 per 100,000 persons per year respectively. The case-mortality rate of brain tumors is 4.4 per 100,000 persons per year. Patients of all age-group develop this cancer. Males are more affected with gliomas than females. Females are more affected with meningiomas. It usually affects individuals of the caucasian race. African Americans are less likely to develop this cancer.

# Risk factors
Brain tumors are associated with a number of predisposing risk factors such as radiation, inherited conditions like neurofibromatosis; von Hippel-Lindau syndrome; Li-Fraumeni syndrome; Turcot syndrome, viruses such as Ebstein-Barr virus, chemicals such as formaldehyde; vinyl chloride; acrylnitrile and genetic factors.

# Natural History, Complications and Prognosis
The complications of brain tumors are brain herniation, loss of brain function and recurrence. The prognosis in primary brain tumors depends on the type of tumor, age, functional status of the patient, the extent of surgical tumor removal, spread of metastasis and biogenetic markers.. Patients with benign gliomas may survive for many years
while survival in most cases of glioblastoma multiforme is limited to a few months after diagnosis. The 5-year survival rate is 33.3%.

# Diagnosis

## Staging and Grading
The subtypes of brain tumors have different staging systems based on the grade, extent of spread, size and presence of distant metastases. The grades of brain tumors are subdivided into Grades 1,2,3 and 4. The lower the grade, better the prognosis.

## History and Symptoms
The most common symptoms of brain tumors are headache, seizures, visual changes and changes in personality, mood and concentration.

## Physical examination
Common physical examination findings of brain tumors include altered sense of consciousness, anisocoria, papilledema and focal neurological deficits.

## CT
Imaging plays a central role in the diagnosis of brain tumors. On head CT scan, brain cancer is characterized by hypodense mass lesions.

## MRI
Imaging plays a central role in the diagnosis of brain tumors. On MRI brain, brain tumor is characterized by hypointense or isointense on T1-weighted scans, or hyperintense on T2-weighted MRI.

## Other imaging findings
The other imaging modalities that can be used for brain tumors are single-photon emission computed tomography, positron emission tomography and whole bone scan.

## Other Diagnostic Studies
Electrophysiological exams, such as electroencephalography play a marginal role in the diagnosis of brain tumors. The definitive diagnosis of brain tumor can only be confirmed by histological examination of tumor tissue samples obtained either by means of brain biopsy or open surgery. The histologic examination is essential for determining the appropriate treatment and the correct prognosis.

# Treatment

## Medical Therapy
The predominant therapy for brain tumor is surgical resection. Adjunctive chemotherapy and radiation may be required.

## Surgery
Meningiomas, with the exception of some tumors located at the skull base, can be successfully removed surgically. In more difficult cases, stereotactic radiosurgery, such as Gamma Knife radiosurgery, remains a viable option. Most pituitary adenomas can be removed surgically using a minimally invasive approach through the nasal cavity and skull base (trans-nasal, trans-sphenoidal approach). Larger pituitary adenomas require a craniotomy (opening of the skull) for their removal. Radiotherapy, including stereotactic approaches, is reserved for inoperable cases.