Muscle weakness (hypotonia)

How does a doctor know what is causing my child's muscle weakness?

Your child's doctor will obtain a medical history for your family and your child and will perform a physical examination that will likely include a detailed muscle function and neurological examination. The latter, also called a neuro exam, may be performed with instruments, such as lights and reflex hammers, and usually does not cause any pain to the child.

• assessment of motor and sensory skills
• balance and coordination
• mental status (the child's level of awareness and interaction with the environment)
• reflexes
• functioning of the nerves

Depending on what your child's doctor suspects, the following tests may also be used to find out what's causing your child's muscle weakness:

• Magnetic Resonance Imaging (MRI) – A diagnostic procedure that uses a combination of large magnets, radio frequencies and a computer to produce detailed images of organs and structures within the body. This test is done to rule out any associated abnormalities of the spinal cord and nerves
• Computerized Tomography Scan (also called a CT or CAT scan) – A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce cross-sectional images (often called "slices"), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat and organs. CT scans are more detailed than general X-rays
• Blood tests
• EMG (electromyogram) - a test used to evaluate nerve and muscle function
• EEG (electroencephalogram) - a test that measures the electrical activity in the brain, called brain waves. An EEG measures brain waves through small button electrodes that are placed on your child's scalp
• spinal tap - also called lumbar puncture, a spinal tap is done to measure the amount of pressure in the spinal canal and/or to remove a small amount of cerebral spinal fluid (CSF) for testing. Cerebral spinal fluid is the fluid that bathes your child's brain and spinal cord
• karyotype - This test, a chromosomal analysis from a blood test, is used to determine whether the problem is the result of a genetic disorder
• muscle biopsy - a sample of muscle tissue is removed and examined under a microscope