intermediate spinal muscular atrophy

Intermediate Spinal Muscular Atrophy (SMA) Description

Intermediate spinal muscular atrophy, also known as SMA type 2 or Dubowitz disease, is a genetic neuromuscular disorder that affects certain muscles, causing them to become weak and waste away. This condition typically appears between six months and 18 months of life.

Key Symptoms:

• Muscle weakness, particularly in the legs
• Hypotonia (low muscle tone)
• Worsening muscle weakness over time
• Difficulty with motor skills, such as sitting, rolling, or holding up their heads

Children with intermediate SMA may initially be able to sit and hold up their heads, but they will eventually develop progressive symptoms, including:

• Weakness in the arms, legs, and lower torso
• Muscle atrophy (wasting away)
• Decreased muscle strength and endurance

Important Notes:

• Intermediate SMA is a chronic condition that requires ongoing medical attention.
• Early diagnosis and treatment can help manage symptoms and improve quality of life.

References:

[1] Context 2: Spinal muscular atrophy (SMA) is a disorder affecting the motor neurons—nerve cells that control voluntary muscle movement. These cells are located in the spinal cord. ... SMA type 2 (intermediate SMA): When a child develops spinal muscular atrophy between six and 18 months, the condition is classified as type 2. The child may be able to sit ...

[3] Context 3: Spinal muscular atrophy (SMA) denotes a collection of inherited clinical syndromes causing degeneration of anterior horn cells in the spinal cord with associated destruction of alpha motor cells and presents clinically with characteristic proximal muscle weakness and atrophy.[1]

[4] Context 4: Spinal muscular atrophy (SMA) is characterized by muscle weakness and atrophy resulting from progressive degeneration and irreversible loss of the anterior horn ...

[5] Context 5: When SMA has its onset between the ages of 6 to 18 months and before the child can stand or walk independently, it is called SMA type 2, or intermediate SMA or ...

Intermediate Spinal Muscular Atrophy (SMA) Symptoms

Spinal muscular atrophy (SMA) symptoms can vary in severity, but for individuals with intermediate SMA, the condition typically presents with a range of physical impairments. Here are some common signs and symptoms:

• Muscle weakness: Individuals with intermediate SMA often experience muscle weakness, particularly in the arms and legs [3].
• Difficulty walking: Many people with intermediate SMA have trouble walking or maintaining balance due to muscle weakness and poor coordination [4].
• Clumsiness: Clumsiness and difficulty with fine motor skills are also common symptoms of intermediate SMA [9].
• Respiratory problems: As the disease progresses, individuals with intermediate SMA may experience respiratory difficulties, including shortness of breath and coughing [5].

It's essential to note that these symptoms can vary in severity and progression from person to person. If you or someone you know is experiencing any of these symptoms, it's crucial to consult a healthcare professional for proper diagnosis and treatment.

References:

[3] - Muscle weakness – such as floppy or weak arms and legs [7] [4] - difficulty sitting up, crawling, walking, and controlling head movements [6] [5] - muscle wasting (atrophy) and low muscle tone (hypotonia) that is typically more pronounced in the lower limbs [5] [9] - These children show signs of clumsiness, difficulty walking, and mild muscle weakness, and, if untreated, they may lose the ability to walk independently. [9]

Note: The numbers in square brackets refer to the corresponding search result number from the provided context.

Spinal muscular atrophy (SMA) is a genetic disorder that affects muscle strength and tone, leading to progressive muscle weakness and wasting. Intermediate SMA is a subtype of SMA characterized by a slower progression than the more severe forms.

Diagnostic tests for intermediate SMA:

• Genetic blood tests: These tests can confirm the diagnosis of SMA by detecting mutations or deletions in the SMN1 gene [3]. A genetic blood test can help to identify changes in the SMN1 gene, which is a key indicator of SMA [8].
• Electromyography (EMG): EMG measures the electrical activity of muscles and can be used to rule out other conditions that may cause muscle weakness. In SMA patients, EMG may show abnormal muscle activity patterns [7].
• Nerve conduction study (NCS): NCS measures the speed and strength of nerve impulses and can help diagnose nerve damage or dysfunction.
• Muscle biopsy: A muscle biopsy involves taking a small sample of muscle tissue for examination under a microscope. This test can provide more detailed information about muscle damage and may be necessary to confirm a diagnosis of SMA [7].

Other diagnostic tests:

• Real-time PCR (polymerase chain reaction): Real-time PCR is a molecular genetic testing method that detects the common SMN1 deletion and may also detect SMN2 copy number variations [5].
• Newborn screening (NBS): NBS for SMA primarily involves real-time PCR to detect the common SMN1 deletion. This test can identify an estimated 95% of all SMA cases [3].

Confirming a diagnosis:

A combination of these diagnostic tests, along with clinical evaluation and family history, is typically used to confirm a diagnosis of intermediate SMA.

References:

[3] A simple blood draw test can identify an estimated 95% of all SMA cases by testing for deletion or mutation of both SMN1 genes. [5] First-tier newborn screening for spinal muscular atrophy (SMA). Prenatal testing for SMA. Diagnostic testing to confirm a suspected diagnosis of SMA. [7] Sep 4, 2024 — These tests can include electromyography (EMG), a nerve conduction study (NCS), or muscle biopsy and additional blood tests to help rule out other conditions. [8] Apr 6, 2023 — A genetic blood test can help to confirm changes in the SMN1 gene. Again, EMG, NCV, and muscle biopsy may be necessary for additional diagnostic information.

Spinal Muscular Atrophy (SMA) is a genetic disorder that affects nerve cells, leading to muscle weakness and wasting. Intermediate SMA is a type of SMA that falls between the more severe types and the milder types.

Current Drug Treatments for Intermediate SMA

According to recent studies and FDA approvals, there are currently three medications approved for the treatment of SMA, including intermediate SMA:

• Nusinersen (Spinraza): This medication was first approved in 2016 by the FDA for the treatment of children and adults with SMA. It works by stimulating the production of SMN2 protein, which is essential for muscle function.
• Onasemnogene abeparvovec-xioi (Zolgensma): Approved in 2020, this gene therapy has been shown

Understanding Differential Diagnosis in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a group of genetic diseases that lead to progressive muscle weakness and atrophy, caused by the loss of alpha motor neurons. When diagnosing SMA, it's essential to consider differential diagnoses, which are conditions that may present with similar symptoms.

Differential Diagnoses for Intermediate Spinal Muscular Atrophy

Intermediate spinal muscular atrophy (SMA) is a subtype of SMA characterized by muscle weakness and atrophy resulting from progressive degeneration and irreversible loss of the anterior horn cells in the spinal cord. The following are potential differential diagnoses to consider:

• Charcot-Marie-Tooth disease (CMT): A group of inherited neuromuscular disorders that can cause muscle weakness, atrophy, and sensory deficits.
• Muscular dystrophies: A group of genetic diseases that lead to progressive muscle weakness and degeneration.
• Peripheral neuropathies: Conditions that affect the nerves outside the brain and spinal cord, leading to muscle weakness, numbness, and pain.

Key Features to Distinguish Intermediate SMA from Other Conditions

When differentiating intermediate SMA from other conditions, consider the following key features:

• Age of onset: SMA typically presents in infancy or early childhood, while CMT and muscular dystrophies may present later in life.
• Muscle weakness pattern: SMA is characterized by progressive muscle weakness and atrophy, particularly affecting proximal muscles. In contrast, CMT and muscular dystrophies may cause more distal muscle weakness.
• Sensory deficits: CMT often presents with sensory deficits, which are not typically seen in SMA.

Genetic Testing for Accurate Diagnosis

Accurate diagnosis of intermediate SMA requires genetic testing to identify mutations or deletions in the SMN1 gene. This is essential for distinguishing SMA from other conditions and for providing appropriate genetic counseling.

References:

• [2] Symptoms vary according to subtype of SMA, but common symptoms include weakness, atrophy, hypotonia, and respiratory failure.
• [12] Homozygous deletion at 5q13 (the coding region for the survival motor neuron (SMN1) gene) is responsible for 95% of SMA cases.
• [9] Spinal muscular atrophy (SMA) is a group of inherited neuromuscular disorders characterized by loss of nerve cells in the spinal cord called lower motor neurons.