Information for Patients
Spinal Muscular Atrophy
What is spinal muscular atrophy (SMA)?
Spinal muscular atrophy (SMA) is a group of genetic diseases that damages and kills motor neurons. Motor neurons are a type of nerve cell in the spinal cord and lower part of the brain. They control movement in your arms, legs, face, chest, throat, and tongue.
As the motor neurons die off, your muscles start to weaken and atrophy (waste away). The muscle damage gets worse over time and can affect speaking, walking, swallowing, and breathing.
What are the types of spinal muscular atrophy (SMA) and what are their symptoms?
There are different types of SMA. They are based on how serious the disease is and when the symptoms start:
- Type l is also called Werdnig-Hoffman disease or infantile-onset SMA. It is the most severe type. It is also the most common. Babies with this type usually show signs of the disease before 6 months of age. In more severe cases, the signs show up even before or just after birth (Types 0 or 1A). The babies may have trouble swallowing and breathing and may not move around a lot. They have chronic shortening of muscles or tendons (called contractures). They usually cannot sit up without help. Without treatment, many children with this type will die before 2 years of age.
- Type ll is a moderate to severe type of SMA. It usually first noticed between 6 and 18 months of age. Most children with this type can sit without support but cannot stand or walk without help. They may also have trouble breathing. They can usually live into adolescence or young adulthood.
- Type lll is also called Kugelberg-Welander disease. It is the mildest type that affects children. The signs of the disease usually show up after age 18 months. Children with this type can walk by themselves but may have trouble running, getting up from a chair, or climbing stairs. They may also have scoliosis (curvature of the spine), contractures, and respiratory infections. With treatment, most children with this type will have a normal lifespan.
- Type IV is rare and often mild. It usually causes symptoms after 21 years of age. The symptoms include mild to moderate leg muscle weakness, tremors, and mild breathing problems. The symptoms slowly get worse over time. People with this type of SMA have a normal lifespan.
What causes spinal muscular atrophy (SMA)?
Most types of SMA are caused by a change in the SMN1 gene. This gene is responsible for making a protein that the motor neurons need to be healthy and to function. But when part of the SMN1 gene is missing or abnormal, there isn't enough protein for the motor neurons. This causes the motor neurons to die off.
Most people have two copies of the SM1 gene - one from each parent. SMA normally only happens when both copies have the gene change. If only one copy has the change, there usually aren't any symptoms. But that gene could be passed down from parent to child.
Some of the less common types of SMA may be caused by changes in other genes.
How is spinal muscular atrophy (SMA) diagnosed?
Your health care provider may use many tools to diagnose SMA:
- A physical exam
- A medical history, including asking about family history
- Genetic testing to check for the gene changes that cause SMA
- Electromyography and nerve conduction studies and a muscle biopsy may be done, especially if no gene changes were found
Parents who have a family history of SMA may want to do a prenatal test to check to see whether their baby has an SMN1 gene change. An amniocentesis or in some cases a chorionic villi sampling (CVS) is used to get the sample for testing.
In some states, genetic testing for SMA is part of newborn screening tests.
What are the treatments for spinal muscular atrophy (SMA)?
There is no cure for SMA. Treatments can help manage symptoms and prevent complications. They may include:
- Medicines to help the body make more of the proteins that the motor neurons need
- Gene therapy for children under 2 years of age
- Physical, occupational, and rehabilitation therapy to help to improve posture and the mobility of the joints. These therapies may also improve blood flow and slow muscle weakness and atrophy. Some people may also need therapy for trouble speaking, chewing, and swallowing.
- Assistive devices such as supports or braces, orthotics, speech synthesizers, and wheelchairs to help people stay more independent
- Good nutrition and a balanced diet to help maintain weight and strength. Some people might need a feeding tube in order to get the nutrition they need.
- Breathing support for people who have muscle weakness in the neck, throat, and chest. The support may include devices to help with breathing during the day and to prevent sleep apnea at night. Some people might need to be on a ventilator.
NIH: National Institute of Neurological Disorders and Stroke
General Equivalence Map Definitions
The ICD-9 and ICD-10 GEMs are used to facilitate linking between the diagnosis codes in ICD-9-CM and the new ICD-10-CM code set. The GEMs are the raw material from which providers, health information vendors and payers can derive specific applied mappings to meet their needs.
- Approximate Flag - The approximate flag is on, indicating that the relationship between the code in the source system and the code in the target system is an approximate equivalent.
- No Map Flag - The no map flag indicates that a code in the source system is not linked to any code in the target system.
- Combination Flag - The combination flag indicates that more than one code in the target system is required to satisfy the full equivalent meaning of a code in the source system.
Index of Diseases and Injuries Definitions
- And - The word "and" should be interpreted to mean either "and" or "or" when it appears in a title.
- Code also note - A "code also" note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction.
- Code first - Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.
- Type 1 Excludes Notes - A type 1 Excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
- Type 2 Excludes Notes - A type 2 Excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
- Includes Notes - This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
- Inclusion terms - List of terms is included under some codes. These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
- NEC "Not elsewhere classifiable" - This abbreviation in the Alphabetic Index represents "other specified". When a specific code is not available for a condition, the Alphabetic Index directs the coder to the "other specified” code in the Tabular List.
- NOS "Not otherwise specified" - This abbreviation is the equivalent of unspecified.
- See - The "see" instruction following a main term in the Alphabetic Index indicates that another term should be referenced. It is necessary to go to the main term referenced with the "see" note to locate the correct code.
- See Also - A "see also" instruction following a main term in the Alphabetic Index instructs that there is another main term that may also be referenced that may provide additional Alphabetic Index entries that may be useful. It is not necessary to follow the "see also" note when the original main term provides the necessary code.
- 7th Characters - Certain ICD-10-CM categories have applicable 7th characters. The applicable 7th character is required for all codes within the category, or as the notes in the Tabular List instruct. The 7th character must always be the 7th character in the data field. If a code that requires a 7th character is not 6 characters, a placeholder X must be used to fill in the empty characters.
- With - The word "with" should be interpreted to mean "associated with" or "due to" when it appears in a code title, the Alphabetic Index, or an instructional note in the Tabular List. The word "with" in the Alphabetic Index is sequenced immediately following the main term, not in alphabetical order.