Evaluating and diagnosing nervous system problems can be complex. Many of the same symptoms occur in different ways among the different disorders. And many disorders don't have clear causes, markers, or tests.

Neurological tests to evaluate children may include:

• CT scan. This imaging test uses X-rays and a computer to make images of the body. A CT scan shows detailed images of any part of the body, including the brain, bones, muscles, fat, and organs. CT scans are more detailed than general X-rays. This test can be done quickly. Most children can have a CT scan without sedation.
• Electroencephalogram. This test records the brain's continuous, electrical activity through electrodes attached to the scalp.
• MRI. This test uses a combination of large magnets, radiofrequencies, and a computer to make detailed images of organs and structures within the body. Certain metals can't be used with the magnets in an MRI scanner. Discuss the risk of any implanted devices or hardware with your child's doctor. Also tell the radiology staff. Sometimes your child will need to remove braces or dental devices before an MRI. Talk with your child's doctor to find out if this is needed. MRI studies take longer than CT, and the machine makes a lot of noise. Young children may need to have sedation so that they can stay still throughout the MRI exam. MRI has no radiation exposure.
• Electrodiagnostic tests. These include electromyography and nerve conduction velocity. These studies evaluate and diagnose disorders of the nerves, muscles, and motor neurons. Electrodes are inserted into the muscle, or placed on the skin overlying a nerve, muscle, or muscle group, and electrical activity and muscle response are recorded.
• Positron emission tomography scan. This computer-based imaging test provides a picture of the brain's activity rather than its structure by measuring levels of an injected substance with a tracer molecule, most often glucose.
• Arteriogram (also called angiogram). This test provides an image of arteries and veins going to and through the brain. CT angiography, a newer and less invasive method, is sometimes used.
• Cerebral spinal fluid analysis (also called spinal tap or lumbar puncture). This test takes a sample of cerebrospinal fluid from the spinal cord for testing.
• Evoked potentials. This test records the brain's electrical response to visual, auditory, and sensory stimuli.
• Ultrasound (also called sonography). This test uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels. Ultrasound of the brain can be done only in the first few months of life while the infant's fontanels, or soft spots, are open.
• Neurosonography. This test uses ultra-high frequency sound waves to evaluate structures of the nervous system, including the brain, spinal cord, and other structures.

You can't explain the test to a baby, but you can help them feel more secure during the test by bringing a special blanket, toy, or pacifier. For many of the studies, sedation or anesthesia is used, which needs the child to fast before the procedure. You may breastfeed your baby or give them a bottle of juice or formula once the technician tells you your baby can eat.

Young children remember things for only a short time, so the best time to talk about the test is right before you are ready to come to the hospital. Explain to your child that you are going to the hospital to have some pictures taken that the doctor needs to help them get better. Try to use simple words. For tests that need the child to be still, such as a CT, MRI, or lumbar puncture, sedation or anesthesia may be used to make sure of a good quality image and prevent pain. It's important to be honest with your child. If the test will be uncomfortable, be sure to talk about it and tell them it is okay to cry. Because children at this age are afraid of being separated from their parent, let them know that you will stay with them as much as possible. When you come to the hospital, bring a favorite book, toy, or blanket.

School-aged children have good imaginations. If you don't tell them the truth, they may imagine something much worse than the actual test. The day of the test, tell your child that they will be going to the hospital to have some pictures taken. Tell them that the pictures will help the doctor decide how to make them better. Use simple words. Be honest. Try to tell your child exactly what will happen. If your child's test is going to be uncomfortable, be sure to tell them it's okay to cry. When you come to the hospital, bring along a favorite book, toy, or game. Depending on the age and emotional maturity of the child, sedation or anesthesia may be used.