Muscle Weakness (Hypotonia)

What are the symptoms of muscle weakness?

The following are common symptoms associated with hypotonia. Each child may experiences symptoms differently. Symptoms vary depending on the underlying cause of the problem.

• decreased muscle tone; muscles feel soft and doughy
• ability to extend limb beyond its normal limit
• failure to acquire motor-related developmental milestones (such as holding head up without support from parent, rolling over, sitting up without support, walking)
• problems with feeding (inability to suck or chew for prolonged periods)
• shallow breathing
• mouth hangs open with tongue protruding (under-active gag reflex)

Some hypotonias are not progressive and are of an unknown origin, a condition known as benign congenital hypotonia.

• Central nervous system function and intelligence in children is normal.
• Children with benign congenital hypotonia may not experience developmental delay.
• Some children acquire gross motor skills (sitting, walking, running, jumping) more slowly than most.

The signs and symptoms of hypotonia resemble that of other conditions. Always consult a physician for a diagnosis.

What causes muscle weakness?

Hypotonia can be caused by a variety of conditions, including those that involve the central nervous system, muscle disorders, and genetic disorders. Some common causes can include but are not limited to:

• Down syndrome
• muscular dystrophy
• cerebral palsy
• Prader-Willi syndrome
• myotonic dystrophy
• Marfan syndrome
• Tay-Sachs disease

Causes of 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

Diagnostic testing for muscle weakness

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.

How is muscle weakness treated?

Specific treatment for hypotonia will be determined by your child's physician based on:

• your child's age, overall health, and medical history
• the extent of the condition
• the underlying cause of the condition
• your child's tolerance for specific medications, procedures, or therapies
• expectations for the course of the condition
• your opinion or preference.

No specific therapy is required to treat benign congenital hypotonia, but children with this problem may periodically need treatment for common occurrences associated with hypotonia, such as recurrent joint dislocations.

Treatment programs to help increase muscle strength and sensory stimulation programs are developed once the cause of your child's hypotonia is established. Such programs usually involve physical therapy through an early intervention or school-based program among other forms of therapy.