Central Neurotoxicity

Description: The body's nervous system is divided into two systems, the central nervous system and the peripheral nervous system. The central nervous system is also divided into two major parts the brain and spinal cord. Different parts of the brain control different functions. Cancer treatments, including chemotherapy, can produce certain effects on these areas of the brain, including impaired cognitive skills, chemo-induced seizures, and memory loss.

• The cerebral cortex is a sheet of tissue that makes up the outer layer of the brain. This area of the brain is responsible for thought, voluntary movement, language, reasoning, perception.
• The cerebellum is located behind the brain stem and controls functions of movement, balance and posture.
• The brain stem is a general term for the area of the brain between the thalamus and spinal cord. Structures within the brain stem are responsible for the most basic functions of life such as breathing, heart rate and blood pressure.
• The hypothalamus is located at the base of the brain and is only the size of a pea. One important function of the hypothalamus is the control of body temperature. The hypothalamus acts like a "thermostat" by sensing changes in body temperature and then sending out signals to adjust the temperature.
• The thalamus receives sensory information and relays this information to the cerebral cortex. The cerebral cortex also sends information to the thalamus, which then transmits this information to other areas of the brain and spinal cord.
• The limbic system is a group of structures that are important for controlling the emotional response to a given situation.
• The hippocampus is one part of the limbic system that is important for memory and learning.
• The basal ganglia are a group of structures that are important in coordinating movement.
• The midbrain functions to help control vision, hearing, eye movement and body movement.

What is Central Neurotoxicity?

The above is a very basic description of the brain and its functions. We are describing central neurotoxicity as side effects of cancer therapy that interfere with the functions of the central nervous system. Particularly focusing on chemotherapy brain effects of confusion, cognitive problems, memory problems and memory loss, seizures, balance and movement.

Central neurotoxicity can also be caused by a variety of conditions including disease, infection, or injury. If there is a question regarding the cause of the neurological symptoms further evaluation may be needed. Below are listed some common exams that may be used to evaluate the central nervous system.

Common Neurologic Examinations:

• Physical Examination - During a physical examination by the health care professional a neurologic examination may be performed. This can be very brief or more detailed depending on concerns and findings. In general the physical examination is divided into 4 parts; cranial nerve assessment, motor function assessment, sensory function assessment, and assessment of reflexes.
• Cranial nerve assessment: There are 12 cranial nerves and these arise from the brain. Each nerve has its own function and the assessment of the nerves is done by evaluating each function. For example, testing the gag reflex with the tongue depressor is testing the 9th and 10th cranial nerves.
• Motor function assessment is checking a person's gait, muscle strength and coordination. The test where a person is asked to touch their nose then the finger of the examiner, with eyes open then with eyes closed is an example of how coordination may be evaluated.
• Sensory function assessment is checking sensations such as pain, temperature, position sense, crude and fine touch along certain pathways. A test that may be used to evaluate this is asking the person to close their eyes and then using a wisp of cotton, ask the person if they can feel the cotton brushed on the skin.
• Testing reflexes helps to assess the status of the central nervous system, this indicates whether the pathway from the spinal cord to the area stimulated and back is intact. The briskness of response is evaluated.
• Computerized Tomography (CT) Scan - A CT scan may be done of your brain, or another part of your body, if your healthcare provider suggests. This exam is more specific than plain x-rays, as a computer takes pictures, from different angles, to show a cross-sectional view of your brain, or other organs. How it works:
• As you lie on a movable table, a scanner inside of a machine moves around you. X-rays are taken at different angles, as the computer records the pictures. The computer then puts the pictures in a specific order, so that the specialist can interpret the findings.
• Sometimes, you may be given a contrast (dye) solution, either taken by mouth (oral) or injected into a large vein (IV). This helps to improve the picture, and show any abnormalities as the dye passes through your body. Your doctor may want you to drink oral contrast if he or she wants to examine your abdomen or pelvis at the same time another part of your body is examined.
• You may be required to fast (not eat) after midnight the day of the exam, if your abdomen is to be examined. Your healthcare provider will give specific instructions to you.
• Electroencephalogram (EEG) - An EEG is a procedure that records your brain waves during certain activities. The procedure may take only 45 minutes to an hour, and tests your brain waves while you are asleep, awake, or concentrating on certain actions. It is sometimes used during anesthesia. It may be a valuable tool to diagnose your condition. Your healthcare provider may order this test if he or she thinks you may have:
• An infection in your brain
• A seizure disorder
• Changes in your mental status
• A Brain tumor
• Electromyography (EMG) - This test may be ordered by your doctor if you have been experiencing nerve pain, or muscle weakness. An EMG will show the conduction of the nerves and muscles, usually in your arms or legs. An EMG may be ordered if:
• You have a neuromuscular disease, such as Myasthenia Gravis, or Amyotrophic Lateral Sclerosis (ALS, or Lou Gering's disease)
• You have pain, numbness or tingling in your extremities - perhaps as a result of carpal tunnel syndrome, or a disease, such as amyloidosis
• Certain nerve injuries from sports-related activities (Burner's disease)
• Magnetic Resonance Imaging (MRI) - While x-rays are very good at looking at bones and solid structures, an MRI looks, very specifically, at the soft organs, cartilage, eyes and tissues of your body. You may receive an MRI:
• Of the spine - if you are having severe back pain, pain that goes down your leg, and your healthcare provider is worried about the stability of your spine. You may have this done if you have cancer that has gone to your bones (metastasized), or if there is a tumor on your spine. You may also have thinning of the bones (osteoporosis), and you are at risk for breaking a bone or fracturing one or more of the bones in the vertebral column, called vertebrae.
• There are 33 vertebrae, each joined by ligaments. Damage to one or more of these bones may damage the spinal cord, and cause serious problems.
• Of the brain - to look at the brain tissue, to check for cancer, or cancer that may have spread, or if swelling is present. This is also important if your doctor thinks you may have an infection in your eyes or head.
• Of a joint - if you have had injury (from playing sports, walking, or falling down), and you have a lot of pain. This will show if any ligaments or cartilage have been damaged in your body. You may receive an MRI of the shoulder, knee, or any other joints in your body.
• There is no special preparation in many cases, but you should not wear metal to the exam. Avoid all metal inside the MRI machine, including:
• Metal snaps on clothing
• Zippers
• Jewelry
• Watches.
• If you have a pacemaker, metal plates in your body from surgery, or any other type of metal in your body, notify your healthcare provider.
• There is a loud "whirring" noise associated with the MRI machine, which many people find upsetting. While you are undergoing the procedure:
• It helps to wear earplugs or headphones to block out the noise of the machine.
• If you are anxious, close your eyes and take slow, deep, even breaths. Think of things that have relaxed you in the past.
• This procedure takes about 1/2 hour to 1 hour to complete.