The first step in diagnosing a brain or spine tumor involves a physical or neurological exam, so as soon as you suspect symptoms you should consult your doctor.
The complete method for determining the presence of a brain or spine tumor includes:
- A medical or neurological exam to assess your symptoms.
- Imaging (brain or spine scan, such as a MRI or CT scan) shows the size, location and impact of the tumor.
- Evaluation of brain or spine tissue via a biopsy provides more detail about the tumor, such as where it started and whether it is benign (noncancerous) or malignant (cancerous).
The medical or neurological exam entails a series of tests that measure nervous system functions and physical and mental alertness. If the results of this exam are abnormal, a brain or spine scan will be administered by a neurological expert.
A brain or spine scan consists of a picture of internal structures. A specialized imaging machine produces a scan in a manner similar to a digital camera taking a photo. With the use of computer technology, a scan creates an image by photographing the brain or spine from various angles.
Some scans use contrast dye injected into the patient’s vein, which assists the neurosurgeon in differentiating between normal and abnormal tissue. Abnormal or diseased brain or spine tissue absorbs greater amounts of dye than healthy tissue.
A biopsy is the final step in diagnosing a brain or spine tumor. Tumors are classified from the least aggressive (benign) to the most aggressive (malignant).
The cell type of origin or the location of the tumor determines the classification of a brain tumor. Identifying the type of tumor determines the most appropriate type of treatment.
Below we explain in detail each of the above diagnostic steps.
Diagnosing Brain and Spine Tumor Grades
Doctors diagnose brain and spine tumors by types and grades. The grade of a tumor is diagnosed by how the cells look under a microscope, which indicates the characteristics of a tumor’s growth.
Tumor Definitions
- Benign tumors are the least aggressive type and do not contain cancerous cells. They typically grow slowly and generally do not spread.
- Malignant tumors contain cancerous cells and are considered life-threatening as they grow quickly and can invade nearby brain or spinal tissue.
- Primary tumors refer to those that start in the brain or spine. They may spread within these areas but rarely to other organs. Primary tumors are typically more frequent in children and older adults.
- Metastatic or secondary tumors are those that start elsewhere then spread to the brain or spine. These tumors are more common than primary tumors and are seen more in adults than children. They are named by the location in which they begin.
Brain and Spine Tumor Grades
- Grade I tumors are when the tissue is benign and the cells grow slowly. The cells almost look like normal brain cells, and rarely spreads. In some cases, it is possible to remove entirely with surgery.
- Grade II is when the tissue is malignant and the cells look a little more abnormal compared to Grade I tumor cells. It is possible for this type to spread and possibly recur.
- Grade III tumors comprise malignant tissue and actively growing cells (anaplastic). The abnormal cells look very different than healthy cells, and is likely to spread into nearby cells.
- Grade IV tumors look the most abnormal and comprise malignant tissue and fast-growing cells. Metastatic tumors are often Grade IV.
Scans to Diagnose Brain or Spine Tumors
Radiological tests are required for an accurate and positive brain and spine tumor diagnosis. Below are the most common radiological tests used for diagnosing brain and spinal tumors.
X-ray
X-rays may be used for the spine to search for potential causes of pain (e.g., tumors, infections, and fractures). It can also show if any vertebrae are compressing your spinal cord, and to evaluate spine alignment.
X-rays show the structure of the vertebrae and the outline of the joints. However, X-rays are not reliable in diagnosing tumors.
CT or CAT Scan (Computed Tomography)
CT scans can show soft tissue, bone and blood vessels combined. As such, CT images can detect abnormalities, swelling, bleeding and bone and tissue calcification, as well as being effective in determining some types of brain and spine tumors.
The CT scan is a combination of advanced x-ray and computer technology, usually with the use of iodine as a contrast agent. A CT/CAT scan is the diagnostic image created after a computer reads the X-ray, combining various x-ray angles to produce a detailed, three-dimensional image.
For example:
- a CT scan shows the shape and size of the spinal canal, its contents, and the structures around it. It also is good at visualizing the bony structures of the spine.
- a brain CT scan can help identify changes to the skull, internal bleeding or enlarged ventricles (the fluid-filled spaces in the brain). It can also show the size of a tumor.
If a patient cannot have an MRI, for example people with a pacemaker, a CT may be used instead.
PET Scan (Positron Emission Tomography)
Neurosurgeons use PET scans to look at organs and tissues. PET scans can determine the difference between scar tissue, recurring tumor cells, and necrosis (i.e. cells destroyed by radiation treatments).
The PET scan creates a picture of the brain or spine by measuring the rate at which a tumor absorbs glucose (a sugar), which is typically faster than normal cells. This is in contrast to the other imaging techniques, which measure the structure of a brain or spine tumor.
In the case of a PET scan, the patient is injected with deoxyglucose, a substance labeled with radioactive markers. The PET scan relays the measured brain or spine activity to a computer, which creates a live image.
MRI (Magnetic Resonance Imaging)
The MRI uses magnetic fields and computers to scan and capture images of the brain. While it utilizes film, it does not use x-rays.
The scan provides images of various planes, which allows the doctor to create a three-dimensional image of the tumor. An MRI detects signals emitted from both normal and abnormal tissue, which results in clear images of most tumors.
An MRI can show the spinal cord, nerve roots and surrounding areas, as well as enlargement, degeneration, and tumors.
After radiological confirmation of the brain tumor, the only way to determine whether the tumor is benign or malignant is to examine a small tissue sample (extracted through a biopsy procedure) under a microscope. If the tumor is malignant, a biopsy helps determine the cancer’s type, which also determines treatment options.
Biopsy
The biopsy, the most accurate method of obtaining a tumor diagnosis, is administered to determine the type and grade of a tumor.
A biopsy surgically removes a sample of tissue taken from a tumor site in order to be examined under a microscope. The biopsy provides information on the types of abnormal cells present in the tumor.
There are two types of brain biopsy used for diagnosis:
- A craniotomy is performed as part of an open biopsy. A craniotomy consists of removing a piece of the skull in order to gain access to the brain. Following the tumor resection (completely removed) or if the tumor is debulked (partially removed), the bone is usually returned to place.
- A closed biopsy (also referred to as a stereotactic or needle biopsy) may be performed for difficult to reach areas of the brain in which a tumor is located. In a closed biopsy, the neurosurgeon drills a small hole into the skull, through which a narrow hollow needle is passed into the tumor in order to remove a tissue sample.
For spinal tumor biopsies, many are performed using minimally invasive techniques, where a CT scan is used to guide a thin needle into the tumor or surrounding areas.
Once a biopsy sample is obtained, a pathologist examines the tissue under a microscope in order to analyze the brain or spine tissue and make a diagnosis.
If necessary, due to a complicated case or one in which there is more than one grade of tumor cells located in the same tumor, the tissue is sent on for further expert analysis.