Doctors and other medical professionals will use diagnostic tests to see if a brain tumor is causing your child’s symptoms. These tests will include a physical examination, and an MRI (magnetic resonance imaging) which is a scan of the brain. The diagnosis is usually made based on the signs and symptoms in your child, and on the results of the MRI study. When the tumor can be identified on the MRI, a biopsy is not necessary.
These tumors are treated with radiation therapy, which are high-energy X-rays that destroy tumor cells. This treatment can reduce symptoms significantly, but there may be some permanent damage caused by the tumor which can’t be helped. Steroids, another type of drug, are often given to improve some of the symptoms. Surgery is not part of the standard treatment because the tumor has grown within a part of the brain where resection is impossible. The effectiveness of chemotherapy is still uncertain.​​
Diffuse intrinsic pontine gliomas account for about 5-10 out of every 100 brain tumors in children or 10% of all pediatric brain tumors diagnosed each year.
Research studies done to determine whether new drugs, treatments, or vaccines are safe and effective. They are conducted in three phases:

• Phase I – In this phase, small groups of people are treated with a certain dose of a new agent that has been extensively studied in the laboratory. During the trial, the dose is increased group by group to find the highest dose that does not cause harmful side effects. Usually there is no control treatment for comparison. This process determines a safe, appropriate dose for use in Phase II.

• Phase II – This phase provides continued safety testing of a new agent, along with an evaluation of how well it works against a specific type of cancer. The new agent is given to groups of people and is usually compared with a standard treatment.

• Phase III – This phase answers research questions across the disease continuum and includes large numbers of participants so that the differences in effectiveness of the new agent can be evaluated. If the results of this phase merit further use of the new agent, the pharmaceutical company will usually submit a New Drug Application to the FDA.

Pontine brain stem tumors affect the cranial nerves, causing symptoms related to the nerves that supply the muscles of the eye and face, and muscles involved in swallowing. These symptoms include double vision, inability to close the eyelids completely, dropping one side of the face, and difficulty chewing and swallowing. The tumor also affects the "long tracks" of the brain, with resultant weakness of the arms or legs and difficulty with speech and walking. Symptoms usually worsen rapidly because the tumor is rapidly growing.

The diagnosis of these tumors is usually made within a week or 2 of the symptoms.

The classification of a tumor according to its degree of aggressiveness and malignancy which can be helpful in predicting disease behavior and making treatment decisions. Brain tumors are graded on a scale of I to IV: Grade I refers to benign tumors (e.g., acoustic neuroma, menigioma), Grade II refers to low-grade tumors (e.g., low-grade oligodendroglioma), Grade III refers to intermediate-grade tumors (e.g., anaplastic oligodendroglioma), and Grade IV refers to the most malignant and aggressive brain tumors (e.g., glioblastoma).​
A brain tumor is an abnormal mass of tissue in which some cells grow and multiply uncontrollably, apparently unregulated by the mechanisms that control normal cells. The growth of a tumor takes up space within the skull and interferes with normal brain activity. A tumor can cause damage by increasing pressure in the brain, by shifting the brain or pushing against the skull, and by invading and damaging nerves and healthy brain tissue. The location of a brain tumor influences the type of symptoms that occur. This is because different functions are controlled by different parts of the brain. Brain tumors rarely metastasize (spread) to other parts of the body outside of the central nervous system (CNS). The CNS includes the brain and spinal cord.​​
It is located at the bottom of the brain and connects the cerebrum to the spinal cord. The brain stem controls many vitally important functions including motor and sensory pathways, cardiac and respiratory functions, and reflexes.​​
A DIPG is a Diffuse Intrinsic Pontine Glioma or Diffusely infiltrative brain stem gliomas or tumors that are spread throughout the normal structures of the pons (the middle portion of the brain stem), sometimes spreading to the midbrain (the upper portion of the brain stem) or the medulla (the bottom portion of the brain stem). It is the most dreaded pediatric brain tumor.
Because they are difficult to treat, the outcome for brainstem gliomas is poor. After diagnosis, the survival time is on average 9 to 12 months. To improve the outcome, doctors have tried giving higher amounts of radiation, using chemotherapy medicines to kill the tumor cells and clinical trials. Research and funding is needed to achieve better results. When the tumor recurs, the focus of treatment is on managing symptoms to make sure the child is as comfortable as possible.

National Brain Tumor Society