If a person is suspected to have CNS tumor, some investigations are required to confirm the diagnosis of the disease. Further, these investigations help in determining the type of CNS tumor, extent and grade of disease, which in turn help in selecting an appropriate treatment approach.
Following are some commonly used diagnostic tools for CNS tumors:
- Imaging Tests: Imaging tests are the mainstay of diagnosis for CNS tumors. These tests help in scanning the CNS and can accurately diagnose the location, size, and shape of the tumor. These tests play important role in defining the extent of disease. They are employed after treatment to evaluate the treatment efficacy and to detect any signs of disease progression/recurrence.
Magnetic resonance imaging (MRI) scan: This technique provides detailed images of internal body structures using radio waves, strong magnetic field, and gadolinium-based contrast material (which is used via intravenous injection to improve the clarity of the MRI images). This is the most widely used technique for the diagnosis of CNS cancers/tumors because it can provide very detailed images of the brain and spinal cord tissue. Some more advanced MRI techniques are frequently used for the diagnosis of CNS cancers/tumors, which provide important information about the disease. Following are such techniques.
Magnetic resonance angiography (MRA) provides detailed images of the CNS vasculature and is very helpful in planning surgery.
Magnetic resonance spectroscopy (MRS) provides information about the composition in a particular area and can differentiate between the healthy and diseased tissue. It can further signal the type of defect in the suspected area.
Functional MRI (fMRI) highlights the slight change in blood flow in a particular part of the brain activated in real time. Thus, this technique is very helpful in mapping tumor-adjacent areas of the brain that are responsible for specific function, such as speech, though, movement, etc. This can be used for preserving important function by an appropriate planning of the indicated treatment (surgery or radiation).
Computed tomography (CT) scan: In this technique, detailed cross-sectional images of body organs are generated using x-rays with contrast agents. This technique can provide images of the CNS tumor. However, it is not primarily employed for the diagnosis of CNS tumors and is reserved for patients who cannot undergo MRI examination, such as those with an implanted pacemaker, metal fragment, paramagnetic surgical clips, extreme obesity, or those who have fear for closed spaces. This technique can sometimes be used to highlight the CNS vasculature by CT angiography. Also, this technique can be used for determining the extent of disease and for planning the treatment in case radiation therapy is indicated for the treatment.
- Biopsy analysis: Biopsy samples contain a small number of cells or a tiny piece of tissue collected from the affected area with the help of a biopsy instrument. These samples are generally collected simultaneously with the main surgical procedure or sometimes before the main surgical procedure planned for the treatment of CNS tumor. The collected biopsy sample is then tested in a laboratory and can help in establishing the diagnosis of CNS tumor based on the presence of characteristic cells. These samples provide very useful information about the cancer cells such as the type of cancer, the severity of cancerous changes involved, and the presence of specific defective genes or proteins.
- Lumbar Puncture: In this procedure, a sample of cerebrospinal fluid (CSF, a biological fluid that surrounds the brain and spinal cord) is collected with the help of a needle inserted up to the subarachnoid space around the spinal cord through the lower part (lumbar region) of the spine. The collected sample is then analyzed in a laboratory for the presence of cancer cells (or tumor markers). This is generally employed for the CNS tumors that may spread via CSF or for primary CNS lymphomas. The detection of certain tumor markers in the CSF can establish the diagnosis of germ cell tumors. This technique can also be used to deliver a treatment into the CSF, if required.