Spinal Muscular Atrophy (SMA) is a disease of the motoneurons, i.e. the neurons responsible for conscious muscle movements such as running, head movements and swallowing. The disease occurs in approximately 1 in 6,000 births in the population, and about 1 in 40 people carry the disease. SMA affects all skeletal muscles, but the so-called proximal muscles (shoulders, hips, back muscles) are often the most affected. Weakness in the lower limbs is generally greater than in the arms. The swallowing muscles, neck muscles and chewing muscles may also be affected. Sensory perception and skin sensitivity are not affected. Patients' intellectual abilities are also unaffected. On the contrary, SMA patients are often observed to be unusually mentally alert and friendly.
Patients with SMA are divided into 4 groups according to the motor development they have achieved:
Type I - acute infantile form (Werdnig-Hoffmann syndrome)
The diagnosis is usually made in children before the age of 6 months. Progression of the disease occurs in the first few months of life. Spontaneous mobility is reduced to a minimum. Children with SMA I usually do not survive 2 years of life.
Type II - transient late infantile form (chronic type of Werdnig-Hoffmann disease)
The diagnosis of this type of atrophy is usually made before the child reaches the age of 2. These children usually learn to sit up, sometimes they can stand on their own or take their first few steps. However, they are never able to walk on their own, as the level of motor development, including the ability to stand, soon declines. If people with SMA type II receive good care, they live an average of 30-50 years.
Type III - juvenile form (Kugelberg-Welander syndrome)
Type III SMA usually begins in preschool or school age. The disease is usually first manifested by gait disturbances caused by increasing weakness of the leg muscles. Gradually, hand mobility also deteriorates and trunk muscle strength decreases. Between 20 and 40 years of age, patients lose mobility.
Type IV - adult form (Aran-Duchenne syndrome)
In type IV SMA, the first symptoms of the disease usually appear after the age of 35. The progression of the disease is often very slow.
Treatment of SMA
The treatment of spinal muscular atrophy has undergone major changes in recent years, bringing new hope for patients with SMA. Until recently, there was no cure for this disease. In May 2017, the first specific treatment for SMA patients, the drug Spinraza (nusinersen), was registered in Europe. It is now available in the Czech Republic for patients of all ages. In addition to the currently available Spinraza treatment, several other drugs are currently in active clinical research.
