Spinal Muscular Atrophy in Kids

Introduction:

Spinal muscular atrophy is a rare genetic disorder that affects motor neurons of the spinal cord. It causes muscle weakness involving walking, crawling, breathing, and swallowing. The sign and symptoms first present within two years of life. Muscular strength and ability to move are reduced. In addition, the child faces difficulty in feeding and swallowing. There is a progressive and irreversible loss of lower motor neurons. The disease onset is gradual and continues to progress in childhood. It is the second most common neuromuscular disease, and the frequency of carriers is one among sixty people.

What Is Spinal Muscular Atrophy?

Spinal muscular atrophy is a genetic disease with generalized weakness and wasting of the muscles. It affects voluntary muscles, and muscle weakness is more severe in proximal muscles. Muscular atrophy is due to genetic mutation and primarily affects infancy, but it can also develop in young children and adults.

What Causes Spinal Muscular Atrophy?

Spinal muscular atrophy is caused by SMN1 (survival of motor neuron 1) gene mutation. This gene produces a survival motor neuron protein essential for the spinal neurons' growth and functioning. However, gene transformation causes irreversible loss of anterior horn cells of the spinal nerve. As a result, the neurons shrink, and the brain cannot control voluntary movements of the head, neck, arms, and legs. In addition, the muscles do not get signals from the spinal cord, which causes muscle wasting due to lack of use.

What Is the Epidemiology of Spinal Muscular Atrophy?

Spinal muscular atrophy is a rare condition that affects one out of 6,000 to 10,000 children worldwide. A person with spinal muscular atrophy has two copies of the missing or mutated neuron 1 gene (SMN1), and one of the genes comes from the mother and the other from the father. Therefore an adult might have a single copy of the defective or mutated gene that may cause spinal muscular atrophy. It has been found that approximately six million Americans carry the mutated SM1 gene. They have one healthy gene and one defective gene and are called as carriers.

What Are the Various Types of Spinal Muscular Atrophy?

Listed below are the types of spinal muscular atrophy:

• Type One Spinal Muscular Atrophy - Symptoms appear after birth in this type of spinal muscular atrophy. As a result, the children are more prone to respiratory failure and collapsed lungs.

• Type Two Intermediate Atrophy - It is also known as Dubowitz disease. It is seen in the child between six months and eighteen months.

• Type Three Mild Atrophy - It is also known as Kugelbert Welander disease. It is seen during the first eighteen years of life. The symptoms affect the child's ability to walk.

• Type Four - It is the adult form of spinal muscular atrophy. It is usually seen in mid thirty years of the age. There is a slow progression of the symptoms.

What Are the Risk of Spinal Muscular Atrophy?

If there is a family history of spinal muscular atrophy, a child is at risk of developing spinal muscular atrophy. Prenatal tests are advised to determine whether the child suffers from this condition.

What Are the Clinical Features of Spinal Muscular Atrophy?

Listed below are the clinical features of spinal muscular atrophy:

• Floppiness is seen in infants.

• There are fewer body movements.

• Muscle weakness.

• There is a progressive loss of muscle strength and control.

• Abnormal chest and weak respiratory muscles.

• Poor head control.

• An unusual curvature of the spine.

• Difficulty in feeding.

• Difficulty in swallowing.

• At birth, there is a presence of tight joints.

• The body appears to be bell-shaped.

• There is frequent falling when the child starts to walk.

• The child finds difficulty in getting up.

What Are the Complication of Spinal Muscular Atrophy?

Listed below are the complication of spinal muscular atrophy:

• Fracture in long bones.

• Hip dislocation.

• Scoliosis.

• A feeding tube is required in severe cases because of difficulty swallowing and eating.

• Malnutrition.

• Severe Dehydration.

• Pneumonia.

• Ventilation is required if there is a respiratory infection or collapsed lungs.

How to Diagnose Spinal Muscular Atrophy?

Listed below are the diagnostic methods of muscular atrophy:

• Medical History - Detailed medical history, physical examination, and evaluation of symptoms are undertaken.

• Blood Investigation - Blood Investigation is advised to evaluate creatine kinase enzyme. The enzyme is released into the bloodstream due to muscle deterioration.

• Genetic Testing - Routine newborn screening to find the spinal motor neuron gene mutation.

• Electromyogram - Nerve conduction test that measures the electrical activity of the nerve cells.

• Biopsy - Muscle biopsy is performed; a small amount of muscle tissue is incised and sent for laboratory investigation. The histopathology report will show muscle atrophy if present.

How Is Spinal Muscular Atrophy Treated?

The primary treatment goal is to relieve the symptoms and manage the complications. Therefore, a multidisciplinary approach is required. Listed below is the treatment plan:

• Targeted Therapy - It helps slow down the progression of spinal muscular atrophy. Injectable medicine such as Nusinersen and Onasemnogene is administered, which treats the underlying cause of the disease.

• Respiratory Therapy - It is indicated if the child suffers from breathing difficulty. Chest physiotherapy and mechanical ventilation are indicated.

• Nutritional Therapy - Nutrition and calories required for the child's growth. Dietary supplements and tube feeding is advised for the child.

• Muscle Therapy - Physical therapy, exercises, and stretching of the muscles and joints are advised. Splints and braces are indicated for the correction of posture and joint positioning.

• Medications - They are indicated if the child suffers from complications such as gastroesophageal reflux and constipation.

• Disease-Modifying Therapy - Risdiplam is given to stimulate the production of the survival motor neuron protein. It is administered by oral route twice daily.

• Gene Replacement Therapy - It is indicated in children younger than two months. Intravenous infusion of the Onasemnogene is indicated. This therapy helps replace the nonfunctioning survival motor neuron genes with functioning genes.

Conclusion:

The child suffering from spinal muscular atrophy needs care and attention from their parents. The treatment is usually multidisciplinary and requires regular visits to healthcare professionals. Parents should be periodically updated with the child's health status, treatment course, and modalities available for this condition. Lifestyle modifications are advised to manage the symptoms and complications. The child faces a very challenging situation in coping with the disease; therefore, parents should be emotionally supportive. Early diagnosis, proper treatment, and support provided by the family will help improve the child's life.