Evaluation and Diagnosis of Brain Tumors

Medical History and Exam

Brain tumors cause the same symptoms as many other health problems. A history and exam conducted by a healthcare provider can help determine what might be causing certain symptoms and if further testing is needed. A medical history consists of questions regarding a person’s past and present state of health and detailed questions about their current symptoms. A neurological exam is performed to test the functioning of the nervous system and often includes testing of vision, hearing, speech, cognition, strength, sensation, coordination, balance, and reflexes.  If specific abnormalities are discovered during the history and physical, the health care provider will send a patient for a brain scan.     

Imaging

Medical imaging is the creation of a picture (scan) of the internal structures of the body.  A radiologist is a physician who interprets the images. Magnetic resonance imaging (MRI) and computed tomography (CT) are the types of medical imaging most commonly used to evaluate brain tumors. Contrast is often given during MRI or CT scans. Contrast is a substance that is swallowed or injected into the veins before imaging to illuminate tumors.  In fact, it is difficult or impossible to see many tumors without contrast.  People with certain medical conditions will be asked to have a blood test to evaluate their kidney function before receiving contrast.  This is to make certain that their kidneys are working well enough to filter the contrast out of the body after the scan. Scans other than MRI or CT scans may be performed to obtain specific information about a tumor.  The most common types of scans used for the evaluation of brain tumors are the following:

• Magnetic resonance imaging (MRI):  Magnetic fields, radio waves, and computer technology are used to create images of the soft tissues of the brain in great detail.   
  
• Computed tomography (CT):  X-rays and computer technology are used to visualize bone, collections of calcium within tumors, bleeding, and swelling.   
  
• Functional MRI (fMRI): MRI technology is used to generate an image of brain activity according to changes of blood flow in the brain. The purpose of this test is to determine which areas of the brain control certain functions so that these areas can be avoided during surgery.  
  
• Positron Emission Tomography (PET): A type of scan that helps distinguish between tumor cells, necrosis (dead tumor cells), and scar tissue.  
  
• Magnetic Resonance Angiogram/Venography (MRA or MRV): MRI technology is used to create an image of blood vessels in the brain. 
• Magnetic Resonance Spectroscopy/Perfusion: These are specialized MRI-based tests that give information about the metabolic activity of specific areas of the brain, which can help in providing evidence for the presence of a tumor.
  

Biopsy

Medical imaging can verify the presence and show certain features of different types of brain tumors but a biopsy is required to know the tumor type for certain. Knowing the tumor type is essential for initiating treatment of brain tumors, as therapies can be significantly different for different tumor types. In cases where removal of large portions of a tumor may not be possible, a biopsy is a surgical procedure in which a small opening is made in the skull and a needle is inserted into the tumor to obtain a small sample of tumor cells.  Alternatively, tumor specimens (“biopsy”) can be taken during surgery that is intended to remove larger portions of the tumor. During the surgery, an initial evaluation of the biopsy material is performed under a microscope by a pathologist who can often provide a preliminary diagnosis. However, final pathological identification of the tumor often takes up to a week, which is critical for providing an accurate diagnosis so that appropriate treatment can be given.             

Lumbar Puncture (spinal tap) 

In rare cases, a diagnosis can be made for particular tumors if the tumor cells are found within the cerebrospinal fluid (CSF). A lumbar puncture is a procedure that is occasionally performed to obtain a sample of cerebrospinal fluid, the fluid that flows around the brain and spinal cord. Numbing medicine is given. Then, a needle is inserted between the vertebrae of the lower back to obtain cerebrospinal fluid.  The cerebral spinal fluid is sent to a lab to be examined for the presence of tumor cells.  

Audiometry

Audiometry is a test to evaluate hearing.  In cases where a tumor may involve the nerve that carries auditory information from the ear to the brain, audiometry may provide information about whether the tumor has damaged the nerve.

Visual Field Testing (perimetry)

Visual field testing is a test to evaluate vision.  Certain tumors may result in pressure on the optic nerves or areas of the brain involved with transmitting or processing visual information. In these cases, visual field testing may be very helpful for providing baseline information about the extent and location of visual loss, which will help guide treatment.