Related articles: Spinal Muscular Atrophy
Definition
Spinal muscular atrophy is a hereditary neuromuscular disease, characterized by the progressive degeneration of the motoneurons of the anterior horns of the spinal cord and of the motor nuclei of the brain stem. The result is an important muscle weakness which leads to various complications.
This pathology is caused by a genetic aberration that affects a region of chromosome 5 and leads to a production of insufficient levels of a protein called SMN (survival motor neuron). The mode of transmission of spinal muscular atrophy is generally autosomal recessive: the parents are healthy carriers of the genetic defect and present a 25% probability of transmitting the disease to each of the children. However, de novo aberrations can also occur, without there being previous cases in the family.
Most common symptoms and signs *
- Arthrogryposis
- Asthenia
- Muscular atrophy and paralysis
- Muscular atrophy
- Muscle cramps
- Dysphagia
- Dyspnoea
- Muscular collation
- weakness
- Muscular hypotrophy
- Growth delay
- Scoliosis
- Muscle spasms
Further indications
Symptoms of spinal muscular atrophy may begin during childhood or adulthood.
The disease can manifest itself, in particular, in three main forms:
- Type I spinal muscular atrophy (Werdnig-Hoffmann's disease) : it is the most severe form; in this case, the disease is symptomatic within the first 6 months of life. Affected newborns present hypotonia (frequently significant from birth), developmental delay, hyporeflexia, lingual fasciculations, marked difficulty in sucking and swallowing disorders. Muscular weakness is almost always symmetrical and involves first the proximal limbs, then the distal extremities (hands and feet). Patients with spinal type I muscular atrophy are unable to sit without support and never reach ambulation. Furthermore, during the course of the disease, there are serious and progressive signs of respiratory failure, which causes death between the first and fourth year of age.
- Type II spinal muscular atrophy (intermediate form) : symptoms usually occur between 3 and 15 months; some affected children acquire the ability to sit, but cannot walk independently. These patients have muscle weakness with flaccidity and fasciculations, while osteotendinous reflexes are absent. Furthermore, dysphagia and respiratory complications may develop. The progression of the disease can stop, leaving the child with permanent muscle weakness and severe scoliosis.
- Type III spinal muscular atrophy (Wohlfart-Kugelberg-Welander disease) : represents the least severe form; it usually occurs between 15 months and 19 years. The signs are similar to those found in the type I form, but the progression is slower and life expectancy is longer or even normal (the latter depends on the possible development of respiratory complications). Symmetrical loss of strength and atrophy progress from the proximal to the distal regions and are more evident at the level of the lower limbs, arising at the level of the quadriceps and hip flexors. The arms are struck later.
Diagnosis is based on clinical evaluation and can be confirmed by genetic analysis.
The treatment is supportive and is based on a multidisciplinary approach aimed at improving the quality of life. This can include physiotherapy, assisted ventilation and gastrostomy.
