Neuromuscular Dıseases

SPINAL MUSCULAR ATROPHY (SMA)

Prepared by: Dr. Sema Ertan Birsel

What is SMA?

Spinal muscular atrophy (SMA) is a group of genetic disorders characterized by progressive muscle weakness and atrophy due to the loss of motor neurons in the spinal cord.

What Causes SMA?

The Survival Motor Neuron (SMN) gene produces a protein crucial for the survival of motor neurons. There are two copies of the SMN gene located on chromosome 5: SMN1 and SMN2. Damage to the SMN1 gene results in reduced production of the SMN protein, leading to the continued death of motor neurons during late pregnancy and post-birth. SMA is inherited in an autosomal recessive pattern, meaning that both parents must be carriers of the defective gene. In such cases, each child has a 25% chance of being affected.

How Common is SMA?

SMA is the most common genetic disorder affecting the lower motor neurons. While specific data for Turkey is not available, it is estimated that the incidence of SMA is between 1 in 6,000 to 1 in 10,000 births.

Clinical Symptoms of SMA

SMA is divided into four subtypes based on the age of onset and disease progression (Table 1). Motor neurons control skeletal muscle activities such as speech, walking, swallowing, and breathing, as well as movements of the arms, legs, face, chest, throat, and tongue. When lower motor neurons are affected, the muscle that the neuron supplies cannot contract, leading to muscle weakness (paralysis), loss of muscle tone (hypotonia or floppiness), loss of reflexes, and muscle atrophy.

Symptoms may be present from birth or develop within the first few months of life. Motor skill development is usually slow. The pattern of muscle weakness primarily affects the legs more than the arms, and symptoms progress from proximal to distal muscles. Orthopedic complications such as joint contractures, scoliosis, and hip dislocation are common, especially in SMA Type II and III.

Table 1: SMA Subtypes

How is SMA Diagnosed?

The diagnosis of SMA is confirmed through genetic testing, specifically SMN gene analysis, with an accuracy rate of 95-98%.

Treatment for SMA

Current treatments for SMA include RNA-based oligonucleotide therapy and gene therapy.

1. Antisense Oligonucleotide-Based Treatments
2. Gene Therapy

Despite these promising treatments, it is essential to continue focusing on the general health, nutrition, swallowing, lung function, vaccinations, and physical therapy of SMA patients.

Orthopedic Management for SMA Patients

SMA patients should be regularly monitored by orthopedic specialists for the development of scoliosis, joint contractures (shortening of muscles and tendons), and hip dislocation. Bone density is often reduced in these patients, leading to an increased risk of osteoporotic fractures. Scoliosis may require surgical intervention, especially if it further impairs respiratory function. Surgical treatment may also be recommended for hip dislocation and other joint contractures to improve mobility and ambulation.

CHARCOT-MARIE-TOOTH DISEASE (CMT)

Prepared by: Dr. Mehmet Ali Talmaç

What is Charcot-Marie-Tooth Disease?

Charcot-Marie-Tooth disease (CMT) is a genetic disorder characterized by progressive damage to motor and sensory nerves, leading to muscle weakness and loss of touch sensation in various parts of the body. This condition affects approximately 1 in 2,500 individuals. The disease is named after the three doctors—Professor Jean-Martin Charcot (1825-1893), Pierre Marie (1853-1940), and Dr. Howard Tooth (1926-1956)—who described it in 1886.

Genetic Aspects of CMT

As a genetic disorder, the risk of developing Charcot-Marie-Tooth disease is higher if a close family member has the condition. While there is currently no known cure for CMT, researchers have identified several genes associated with the disease.

Diagnosis of CMT

The diagnosis of Charcot-Marie-Tooth disease can often be made based on clinical examination findings. Patients with CMT may exhibit muscle weakness in the feet, ankles, legs, and hands, resulting in abnormal walking patterns, high arches, or flat feet. Additionally, numbness may occur in the feet, arms, and hands.

Treatment Goals

The primary goals of treatment are to preserve the strength of weakened muscles and to prevent or reduce deformities in joints and bones. Initial management usually includes physical therapy, the use of ankle-foot orthoses (AFOs), and appropriate footwear with custom insoles.

Orthopedic Management

Orthopedic treatment is necessary to prevent the development of foot deformities or to achieve a painless, flat-footed position in patients with existing deformities. Potential orthopedic interventions may include tendon transfer surgery, muscle relaxations, bone osteotomies for corrections, or joint fusion surgeries. The specific procedures required will be determined based on clinical examination and X-ray findings.