Low Muscle Tone in Children (Hypotonia)

Low muscle tone is the decreased level of tension in the muscles while at rest. The muscles are very relaxed, thus making movements difficult task for such individuals. In simple words, hypotonia means abnormally low muscle tone.

Hypotonia is a lack of resistance to passive movements, whereas muscle weakness results in impaired active movement. The amount of tension or resistance to movement in a muscle is very low. Hypotonia is derived from the words, hypo means low and tonos, which means to stretch.

Hypotonia is a result of many diseases and disorders affecting motor nerve control by the brain or muscle strength. What are the common features of low muscle tone in children?

• Decreased muscle strength
• Increased flexibility and movement in joints
• Poor endurance at carrying tasks

Types

• Central Hypotonia – Hypotonia originating from within the brain is called central hypotonia.
• Peripheral Hypotonia – Hypotonia having origin within the spinal cord, spinal nerves, peripheral nerves and skeletal muscles is known as Peripheral Hypotonia.
• Benign congenital hypotonia - Some children are born with hypotonia that isn’t related to separate condition. This is called Benign congenital hypotonia. So, it means it’s a condition on its own.

Causes

Some conditions known to cause hypotonia include:

Conditions affecting Brain and Spinal cord

Genetic Disorders

Acquired Causes

Signs and Symptoms

Depending upon the cause, hypotonia occurs in children at any age. The common signs in infants and children are:

Floppy Baby Syndrome - Severe hypotonia in growing children is commonly known as floppy baby syndrome. These children have difficulty in feeding, as their mouth muscles cannot maintain a proper suck-swallow pattern. The kids are unable to maintain flexed ligaments; movement of the head is uncontrollable, etc.

Developmental Delay – Motor skills are delayed in children with hypotonia. Hypotonic infants are late in acquiring milestones and gross motor skills e. g. raising the head while lying on their stomach, rolling over, lifting into a sitting position, remaining seated without falling, balancing, crawling. Fine motor skills delays occur in hypotonic children like in grasping a toy, transferring small object from hand to hand, etc.

Diagnosis

Doctor must first determine if the hypotonia is due to muscle, neuromuscular junction, nerve, or central cause. The aim of diagnosis is to detect the exact cause of the condition.

The mother is asked about her pregnancy and if family member had hypotonia or if the baby suffered seizures after birth.

History of trauma at birth is asked, premature delivery, late cry of the baby after birth, abnormal pH of cord blood, etc. are also relevant findings to diagnose hypotonia. The following tests are carried out:

Electromyography (EMG) - Electrical activity of a muscle is recorded using needle like electrodes which are inserted into the muscle fibers.

Nerve conduction velocity – The speech of conduction of a nerve impulse is measured with small metal electrodes placed over the skin over the nerve.

Treatment

Hypotonia is a medical condition that can be helped with early treatment intervention. The earlier it is diagnosed, the easier it is for treatment. Proper cause is to be found, once cause is determined, it is good for treatment.

As the specific cause gets known, treatment is directed toward the particular cause. This is followed by symptomatic and supportive therapy for the hypotonia. The degree of low muscle tone can vary from one child to the next. Early intervention is important for children with low muscle tone problems.

At school, the child with hypotonia is going to have a difficult time keeping and maintaining an upright posture. It’s needed to modify the environment to help with decreased trunk muscles. Occupational therapist is very useful in treating the distressing signs and symptoms of dystonia.