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Spinal Muscular Atrophy (SMA) in Children

by Brian Alverson, MD
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    00:02 When children are weak, sometimes the problem is in the motor nerve.

    00:06 In this lecture, we'll talk about specific motor nerve disorders that could occur in pediatrics.

    00:13 Let's start with Spinal Muscular Atrophy or SMA.

    00:18 SMA is often a very debilitating condition.

    00:22 it's autosomal recessive in that it may travel in families.

    00:26 and have unaffective carriers.

    00:29 The defect is on the survival motor neuron gene or the SMN gene It results in a degeneration of the anterior horn cells of the spinal cord.

    00:40 resulting in weakness.

    00:43 There are three main types of SMA.

    00:46 I, II and III.

    00:47 SMA I is very severe.

    00:50 It usually affects infants and is often life threatening.

    00:55 SMA II is more moderate and SMA III is quite mild.

    01:01 All of the SMAs, the problem is that small muscles are not innervated.

    01:06 The larger ones still have innervations.

    01:09 So, in muscle biopsy it will show a patchy appearance.

    01:13 Much like this.

    01:14 Patients will present with a progressive symmetrical proximal weakness.

    01:20 Remember this is a lower motor neuron disease.

    01:23 So, they will be floppy and may have absent deep tendon reflexes.

    01:29 You may see muscle fasciculation as well.

    01:31 And it is often seen easily in the tongue.

    01:35 But remember, it is just the motor neurons.

    01:37 These patients will have normal cognition.

    01:41 So, let's review the three types.

    01:44 Type one results in severe hypotonia in children.

    01:47 It generally presents before six months of age and death before the age of two is common.

    01:54 These children will often die of respiratory complications.

    02:00 In Type II disease, they may have the ability to sit but often will not have the ability not walk.

    02:06 This typically presents a little later around 6-18 months of age.

    02:11 And it requires nutrition and respiratory support.

    02:16 In Type III disease, patients may lose the ability to ambulate around 10 years of age.

    02:23 It often presents after a year an a half of age and typically we will involve Physical therapy and orthopedics for braces or things like that so to they can function as long and as well as possible.

    02:37 So, the diagnosis of SMA is made by a genetic test of the SMA I gene.

    02:44 We'll send it for sequencing and look for deletions.

    02:49 Therapy is really only supportive. There is no known cure for this condition.

    02:55 And thoughtful palliative care is needed especially for SMA I.

    03:00 There are interventions we can make in children who have no tone but who have an end mortality that is likely within the first few years of life.

    03:10 Examples are G-tubes or breathing machines or tracheostomies.

    03:15 The challeng is that each intervention may cause a different way that that child maybe spending their life uncomfortably.

    03:23 This is a very challenging situation for families who thought they were having a normal child.

    03:28 and palliative care experts can be very very beneficial in helping to guide therapy.


    About the Lecture

    The lecture Spinal Muscular Atrophy (SMA) in Children by Brian Alverson, MD is from the course Pediatric Neurology.


    Included Quiz Questions

    1. It is an autosomal recessive disorder.
    2. It is a defect in the super motor nerve gene (SNM).
    3. It is the least severe type.
    4. Children with this disease usually live until their teen years.
    5. There is degeneration of the motor cortex in the brain.
    1. SMA I
    2. SMA II
    3. SMA III
    4. SMA IV
    5. SMA V
    1. Distal muscle weakness
    2. Progressive and symmetrical
    3. Absent deep tendon reflexes
    4. Normal cognition
    5. Fasciculation in the tongue
    1. Physiotherapy and orthopaedic care.
    2. Nutritional supplements with respiratory support.
    3. Only respiratory support.
    4. High dose steroids.
    5. IV plasmapheresis
    1. It is due to the degeneration of the anterior horn cells of the spinal cord.
    2. It is an upper motor neuron lesion.
    3. Large muscles are not innervated, while small muscles are innervated.
    4. Dystrophin protein is not present in muscle fibers
    5. It is an autosomal dominant inherited disease.
    1. Type III SMA
    2. GBS
    3. Polio
    4. Type I SMA
    5. Type II SMA

    Author of lecture Spinal Muscular Atrophy (SMA) in Children

     Brian Alverson, MD

    Brian Alverson, MD


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