It is recommended that children with TSC be screened for SEGA with neuroimaging every 1–3 years.

Medical imaging plays a central role in the diagnosis of brain tumors. Early imaging methods – invasive and sometimes dangerous – such as pneumoencephalography and cerebral angiography have been abandoned in favor of non-invasive, high-resolution techniques, especially magnetic resonance imaging (MRI) and computed tomography (CT) scans. Neoplasms will often show as differently colored masses (also referred to as processes) in CT or MRI results.

- Benign brain tumors often show up as hypodense (darker than brain tissue) mass lesions on CT scans. On MRI, they appear either hypodense or isointense (same intensity as brain tissue) on T1-weighted scans, or hyperintense (brighter than brain tissue) on T2-weighted MRI, although the appearance is variable.

- Contrast agent uptake, sometimes in characteristic patterns, can be demonstrated on either CT or MRI scans in most malignant primary and metastatic brain tumors.

- Pressure areas where the brain tissue has been compressed by a tumor also appear hyperintense on T2-weighted scans and might indicate the presence a diffuse neoplasm due to an unclear outline. Swelling around the tumor known as "peritumoral edema" can also show a similar result.

This is because these tumors disrupt the normal functioning of the BBB and lead to an increase in its permeability. However, it is not possible to diagnose high- versus low-grade gliomas based on enhancement pattern alone.

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 histological examination is essential for determining the appropriate treatment and the correct prognosis. This examination, performed by a pathologist, typically has three stages: interoperative examination of fresh tissue, preliminary microscopic examination of prepared tissues, and follow-up examination of prepared tissues after immunohistochemical staining or genetic analysis.

An X-ray computed tomography (CT) or magnetic resonance imaging (MRI) scan is necessary to characterize the extent of these tumors (size, location, consistency). CT will usually show distortion of third and lateral ventricles with displacement of anterior and middle cerebral arteries. Histologic analysis is necessary for grading diagnosis.

In the first stage of diagnosis the doctor will take a history of symptoms and perform a basic neurological exam, including an eye exam and tests of vision, balance, coordination and mental status. The doctor will then require a computerized tomography (CT) scan and magnetic resonance imaging (MRI) of the patient's brain. During a CT scan, x rays of the patient's brain are taken from many different directions. These are then combined by a computer, producing a cross-sectional image of the brain. For an MRI, the patient relaxes in a tunnel-like instrument while the brain is subjected to changes of magnetic field. An image is produced based on the behavior of the brain's water molecules in response to the magnetic fields. A special dye may be injected into a vein before these scans to provide contrast and make tumors easier to identify.

If a tumor is found, it will be necessary for a neurosurgeon to perform a biopsy on it. This simply involves the removal of a small amount of tumor tissue, which is then sent to a neuropathologist for examination and grading. The biopsy may take place before surgical removal of the tumor or the sample may be taken during surgery. Grading of the tumor sample is a method of classification that helps the doctor to determine the severity of the astrocytoma and to decide on the best treatment options. The neuropathologist grades the tumor by looking for atypical cells, the growth of new blood vessels, and for indicators of cell division called mitotic figures.

Diagnosis is made by imaging with a contrast-enhanced MRI or CT scan of the brain.

The risk of meningioma can be reduced by maintaining a normal body weight, and by avoiding unnecessary dental x-rays.

PXA is diagnosed through a combination of diagnostic processes:

- Initially, a doctor will interview the patient and do a clinical exam, which will include a neurological examination.

- A CT scan of the brain, and/or an MRI scan of the brain and spine, will be performed. A special dye may be injected into a vein before these scans to provide contrast and make tumors easier to see.

- For children experiencing seizures, an EEG might be part of the diagnostic process (the goal being to record the brain's electrical activity in order to identify and localize seizure activity).

- Finally, a biopsy of the tumor, taken through a needle during a simple surgical procedure, helps to confirm the diagnosis.

There are no precise guidelines because the exact cause of astrocytoma is not known.

Usually—depending on the interview of the patient and after a clinical exam which includes a neurological exam, and an ophthalmological exam—a CT scan and or MRI scan will be performed. A special dye may be injected into a vein before these scans to provide contrast and make tumors easier to identify. The neoplasm will be clearly visible.

If a tumor is found, it will be necessary for a neurosurgeon to perform a biopsy of it. This simply involves the removal of a small amount of tumorous tissue, which is then sent to a (neuro)pathologist for examination and staging. The biopsy may take place before surgical removal of the tumor or the sample may be taken during surgery.

Observation with close imaging follow-up may be used in select cases if a meningioma is small and asymptomatic. In a retrospective study on 43 patients, 63% of patients were found to have no growth on follow-up, and the 37% found to have growth at an average of 4 mm / year. In this study, younger patients were found to have tumors that were more likely to have grown on repeat imaging; thus are poorer candidates for observation. In another study, clinical outcomes were compared for 213 patients undergoing surgery vs. 351 patients under watchful observation. Only 6% of the conservatively treated patients developed symptoms later, while among the surgically treated patients, 5.6% developed persistent morbid condition, and 9.4% developed surgery-related morbid condition.

Observation is not recommended in tumors already causing symptoms. Furthermore, close follow-up with imaging is required with an observation strategy to rule out an enlarging tumor.

An X-ray computed tomography (CT) or magnetic resonance imaging (MRI) scan is necessary to characterize the anatomy of this tumor as to size, location, and its heter/homogeneity. However, final diagnosis of this tumor, like most tumors, relies on histopathologic examination (biopsy examination).

The majority of patients can be expected to be cured of their disease and become long-term survivors of central neurocytoma. As with any other type of tumor, there is a chance for recurrence. The chance of recurrence is approximately 20%. Some factors that predict tumor recurrence and death due to progressive states of disease are high proliferative indices, early disease recurrence, and disseminated disease with or without the spread of disease through the cerebral spinal fluid. Long-term follow up examinations are essential for the evaluation of the outcomes that each treatment brings about. It is also essential to identify possible recurrence of CN. It is recommended that a cranial MRI is performed between every 6–12 months.

If resected, the surgeon will remove as much of this tumor as possible, without disturbing eloquent regions of the brain (speech/motor cortex) and other critical brain structure. Thereafter, treatment may include chemotherapy and radiation therapy of doses and types ranging based upon the patient's needs. Subsequent MRI examination are often necessary to monitor the resection cavity.

The prognosis for gliomatosis cerebri is generally poor. Surgery is not practical considering the extent of the disease, standard chemotherapy (nitrosourea) has been unsuccessful, and while brain irradiation can stabilize or improve neurologic function in some patients, its impact on survival has yet to be proven.

In 2014, Weill Cornell Brain and Spine Center launched an international registry for Gliomatosis Cerebri, where tissue samples can be stored for genomic study.

Most of the brain is separated from the blood by the blood-brain barrier (BBB), which exerts a restrictive control as to which substances are allowed to pass. Therefore, many tracers that reach tumors in the body very easily would only reach brain tumors once there is a disruption of the BBB. Thus the disruption of the BBB, which can be detected by MRI and CT, is regarded as the main diagnostic indicator for malignant gliomas, meningiomas, and brain metastases.

Although there is no specific or singular clinical symptom or sign for any brain tumors, the presence of a combination of symptoms and the lack of corresponding clinical indications of infections or other causes can be an indicator to redirect diagnostic investigation towards the possibility of an intracranial neoplasm. Brain tumors have similar characteristics and obstacles when it comes to diagnosis and therapy with tumors located elsewhere in the body. However, they create specific issues that follow closely to the properties of the organ they are in.

The diagnosis will often start by taking a medical history noting medical antecedents, and current symptoms. Clinical and laboratory investigations will serve to exclude infections as the cause of the symptoms. Examinations in this stage may include the eyes, otolaryngological (or ENT) and electrophysiological exams. The use of electroencephalography (EEG) often plays a role in the diagnosis of brain tumors.

Swelling or obstruction of the passage of cerebrospinal fluid (CSF) from the brain may cause (early) signs of increased intracranial pressure which translates clinically into headaches, vomiting, or an altered state of consciousness, and in children changes to the diameter of the skull and bulging of the fontanelles. More complex symptoms such as endocrine dysfunctions should alarm doctors not to exclude brain tumors.

A bilateral temporal visual field defect (due to compression of the optic chiasm) or dilation of the pupil, and the occurrence of either slowly evolving or the sudden onset of focal neurologic symptoms, such as cognitive and behavioral impairment (including impaired judgment, memory loss, lack of recognition, spatial orientation disorders), or emotional changes, hemiparesis, hypoesthesia, aphasia, ataxia, visual field impairment, impaired sense of smell, impaired hearing, facial paralysis, double vision, or more severe symptoms such as tremors, paralysis on one side of the body hemiplegia, or (epileptic) seizures in a patient with a negative history for epilepsy, should raise the possibility of a brain tumor.

With treatment, pleomorphic xanthoastrocytomas are associated with a high rate of cure.

- Grade II pleomorphic xanthoastrocytomas are known to progress towards grade II tumors, which are more likely to recur after surgical removal.

- Grade III anaplastic pleomorphic xanthoastrocytomas may evolve and show signs of anaplasia, according to evidence in the medical literature.

Like most tumors in the brain, astroblastoma can be treated through surgery and various forms of therapy. Many publications within the last decade have suggested a noticeable improvement in success rate of patients. With the advancement of cutting-edge technology and novel approaches in stem cells, patients are hopeful that they be happy and healthy through old age.

The following factors influence an oncologist's specific treatment plan:

1. Patient's overall medical history

2. Localization and grade severity of the tumor

3. Age and tolerance to certain medications, procedures, and treatment

4. Predicted progress of recovery

5. Final anticipated outcome of treatment

The primary diagnosis is made with a computed tomography scan (CT scan). On a scan, hemangioblastoma shows as a well-defined, low attenuation region in the posterior fossa with an enhancing nodule on the wall. Sometimes multiple lesions are present.

Microscopically, an astrocytoma is a mass that looks well-circumscribed and has a large cyst. The neoplasm may also be solid.

Under the microscope, the tumor is seen to be composed of bipolar cells with long "hairlike" GFAP-positive processes, giving the designation "pilocytic" (that is, made up of cells that look like fibers when viewed under a microscope). Some pilocytic astrocytomas may be more fibrillary and dense in composition. There is often presence of Rosenthal fibers, eosinophilic granular bodies and microcysts. Myxoid foci and oligodendroglioma-like cells may also be present, though non-specific. Long-standing lesions may show hemosiderin-laden macrophages and calcifications.

The histopathologic grading of oligodendrogliomas is controversial. Currently the most commonly used grading schema is based on year 2007 World Health Organization (WHO) guidelines. An updated classification is in progress. Oligodendrogliomas are generally dichotomized into grade II (low grade) and grade III (high grade) tumors. The designation of grade III oligodendroglioma (high grade) generally subsumes the previous diagnoses of anaplastic or malignant oligodendroglioma.

Unfortunately, the WHO guidelines include subjective criteria in differentiating grade II and grade III tumors including the appreciation of "significant" hypercellularity and pleomorphism in the higher grade lesion. In addition, the presence of low mitotic activity, vascular proliferation and necrosis, including pseudopallisading necrosis are insufficient by themselves to elevate the grade of these tumors. This leads to inevitable interobserver variability in diagnosis by pathologists. The ultimate responsibility for making treatment decisions and interpretation of these diagnoses lies with the oncologist in consultation with the patient and their family.

It has been proposed that WHO guidelines should contain a category for grade IV oligodendrogliomas which essentially appear to be glial neoplasms with overwhelming features of glioblastoma multiforme (GBM) arising from known lower grade oligodendrogliomas or GBM with a significant proportion of oligodendroglial differentiation. The diagnostic utility of this latter category is uncertain as these tumors may behave either like glioblastoma or grade III oligodendrogliomas. As such, this is an exceptionally unusual diagnosis.

The updated WHO guidelines published in 2007 recommends classifying such tumors for the time being as 'glioblastoma with oligodendroglioma component'. It remains to be established whether or not these tumors carry a better prognosis than standard glioblastomas.

The standard work-up for AT/RT includes:

- Magnetic resonance imaging (MRI) of the brain and spine

- Lumbar puncture to look for M1 disease

- Computed tomography (CT) of chest and abdomen to check for a tumor

- Bone marrow aspiration to check for bone tumors. Sometimes the physician will perform a stem cell transplant

- Bone marrow biopsy

- Bone scan

The initial diagnosis of a tumor is made with a radiographic study (MRI or CT-). If CT was performed first, an MRI is usually performed as the images are often more detailed and may reveal previously undetected metastatic tumors in other locations of the brain. In addition, an MRI of the spine is usually performed. The AT/RT tumor often spreads to the spine. AT/RT is difficult to diagnose only from radiographic study; usually, a pathologist must perform a cytological or genetic analysis.

Examination of the cerebrospinal fluid is important (CSF), as one-third of patients will have intracranial dissemination with involvement of the CSF. Large tumor cells, eccentricity of the nuclei, and prominent nucleoli are consistent findings. Usually only a minority of AT/RT biopsies have rhabdoid cells, making diagnosis more difficult. Increasingly it is recommended that a genetic analysis be performed on the brain tumor, especially to find if a deletion in the INI1/hSNF5 gene is involved (appears to account for over 80% of the cases). The correct diagnosis of the tumor is critical to any protocol. Studies have shown that 8% to over 50% of AT/RT tumors are diagnosed incorrectly.

Before the advent of MRI, diagnosis was generally not established until autopsy. Even with MRI, however, diagnosis is difficult. Typically, gliomatosis cerebri appears as a diffuse, poorly circumscribed, infiltrating non-enhancing lesion that is hyperintense on T2-weighted images and expands the cerebral white matter. It is difficult to distinguish from highly infiltrative anaplastic astrocytoma or GBM.

Treatment options include surgery, radiotherapy, radiosurgery, and chemotherapy.

The infiltrating growth of microscopic tentacles in fibrillary astrocytomas makes complete surgical removal difficult or impossible without injuring brain tissue needed for normal neurological function. However, surgery can still reduce or control tumor size. Possible side effects of surgical intervention include brain swelling, which can be treated with steroids, and epileptic seizures. Complete surgical excision of low grade tumors is associated with a good prognosis. However, the tumor may recur if the resection is incomplete, in which case further surgery or the use of other therapies may be required.

Standard radiotherapy for fibrillary astrocytoma requires from ten to thirty sessions, depending on the sub-type of the tumor, and may sometimes be performed after surgical resection to improve outcomes and survival rates. Side effects include the possibility of local inflammation, leading to headaches, which can be treated with oral medication. Radiosurgery uses computer modelling to focus minimal radiation doses at the exact location of the tumor, while minimizing the dose to the surrounding healthy brain tissue. Radiosurgery may be a complementary treatment after regular surgery, or it may represent the primary treatment technique.

Although chemotherapy for fibrillary astrocytoma improve overall survival, it is effective only in about 20% of cases. Researchers are currently investigating a number of promising new treatment techniques including gene therapy, immunotherapy, and novel chemotherapies.

The prognosis for brain metastases is variable. It depends on the type of primary cancer, the age of the patient, the absence or presence of extracranial metastases, and the number of metastatic sites in the brain. For patients who do not undergo treatment the average survival is between one and two months. However, in some patients, such as those with no extracranial metastases, those who are younger than 65, and those with a single site of metastasis in the brain only, prognosis is much better, with median survival rates of up to 13.5 months. Because brain metastasis can originate from various different primary cancers, the Karnofsky performance score is used for a more specific prognosis.

Neuroimaging, such as MRI, is the main diagnostic tool for brain stem gliomas. In very rare cases, surgery and biopsy are performed.

Craniopharyngiomas are usually successfully managed with a combination of adjuvant chemotherapy and neurosurgery. Recent research describes the rare occurrence of malignant transformations of these normally benign tumors. Malignant craniopharyngiomas can occur at any age, are slightly more common in females, and are usually of the adamantinomatous type.

The malignant transformations can take years to occur (although 1 in 5 of the diagnosed cases were de novo transformations), hence the need for lengthier follow up in patients diagnosed with the more common benign forms.

There was no link found between malignancy and initial chemo-radiotherapy treatment, and the overall survival rate was very poor with median survival being 6 months post diagnosis of malignancy.