Muscular Dystrophy Flashcards
0
Q
What is muscular dystrophy?
A
- Refers to a group of hereditary myopathies characterized by progressive muscle weakness as a result of deterioration and destruction of muscle fibers. It is generally gradual and cumulative. (don’t have the same amount of contractility)
- The primary impairment is weakness secondary progressive loss of myofibrils and the resultant loss of contractility.
1
Q
Myopathy
A
-primary ms disorder - affects ms fiber itself
2
Q
Reasons for Myopathy
A
- inherited
- autoimmune damage
- infection
- toxin
3
Q
Characteristics of MD
A
- Each form is unique/degree of muscle fiber destruction is variable
- All have decreased protein necessary for normal cell metabolism
- No bowel/bladder problems
- No sensation impairments
4
Q
Criteria for Classification
A
- Mode of inheritance (X chromosomme = sex linked)
- Age of onset (born with it, but effect is later)
- Rate of progression (of weakness)
- Localization of involvement/symptom (what impairments? where? (proximal or distal))
- Involvement of other organ systems (ex: cardiopulmonary)
5
Q
MDA Recognizes 9 Primary Types
A
- Duchenne (most common form)
- Becker’s
- Limb Girdle
- Myotonic
- FSH
- Congenital
- Distal
- Oculopharyngeal
- Emery-Driefus
6
Q
DMD Incidence
A
- 85% of all MDs
- 1 in 3500 live male births (worldwide)
- new mutation rate of 1 in 10,000. 1/3 or more in families with no history (could be mutation in mother or baby)
- Female “manifesting carrier”
7
Q
DMD Pathology
A
- Affected gene fails to make dystrophin (necessary for normal cell metabolism)
- Absence of dystrophin leads to: increased cell permeability, rise of CA+, this activates destructive enzymes, results in cell destruction
- (need dystrophin to make normal muscle cells)
8
Q
Cell Destruction Results In
A
- Loss of ms fiber
- Loss of fiber variation (type II more affected) (fast twitch)
- Pseudohypertrophy: ms fiber replaced with adipose and connective tissue (seen most in calf ms, lays down fat and connective tissue = illusion of hypertrophied calf)
9
Q
MD Inheritance Pattern
A
- With each pregnancy: 50% daughters unaffected, 50% daughters carriers, 50% sons unaffected, 50% sons affected
- No females with DMD
- Manifesting carriers - may experience mild ms weakness, may have cardiac problems, most however do no exhibit symptoms
- MD - sex linked - carried on X chromosome
- 1 in 50 million chance of female with DMD
10
Q
DMD Rate of Progression/ 3 Phases
A
- Early: diagnosis to marked functional changes
- Transitional: marked postural changes to inability to walk (5-12)
- Non-ambulatory: uses power WC for mobility
11
Q
DMD Localization of Involvement
A
- Progressive muscle weakness
- Proximal to distal
- Breakdown of ms into adipose and connective tissue
- Eventually affects all muscles (including ms of respiration)
12
Q
DMD Other Organ Systems
A
- Skeletal
- Cardiopulmonary
- Brain
13
Q
DMD - Skeletal
A
- Scoliosis
- for boys not tx with Prednisone, 90% chance of significant progressive scoliosis (Prednisone is the primary treatment)
- Osteoporosis (secondary to Prednisone) - increased risk of vertebral compression fx
14
Q
DMD - Cardiopulmonary
A
- Usually see cardiomyopathy and/or cardiac arrhythmia - may not be symptomatic due to low activity requirement (not placing a lot of demands on the heart)
- Declining respiratory function - vital capacity declines over time (trouble ventilating, abdominals - ineffective)
- Usual cause of death is pure respiratory failure or secondary to infection age 18-25
15
Q
DMD - The Brain
A
- 1/3 - some degree of learning disability: attention, verbal learning and memory, emotional interaction (immature)
- May be due to dystrophin abnormality in the brain (don’t really know why)
16
Q
DMD Diagnosis
A
- Pt/family hx and physical exam
- Increased CK level -creatine kinase - leaks out of damaged ms
- Ms biopsy - can distinguish MD from inflammatory/other disorders or other forms of MD
- DNA diagnostics - used to confirm diagnosis of DMD/establish carrier status
17
Q
DMD - Early Phase
A
- Usually identified age 2-5 unless family hx
- Attain early dev milestones
- Noticeable when he begins to walk, thought to be clumsy
- By 3-4, problem undeniable
18
Q
Early Phase - Functional Limitations
A
- Frequent falling - with running, jumping, climbing, uneven surfaces
- Difficulty getting up from floor - Gower’s sign
- Impaired posture/gait - lordosis, “waddling gait”, up on toes, wide BOS
- Difficulty pushing/pulling, lifting (because of weakness) - Meryon’s sign
(weak scapular stabilizers, slide out from hands when try to pick them up)
19
Q
Early Phase - Impairments
A
- Muscle weakness: LE (quads, gluts, ant tib), UE (scapular stabilizers), trunk (lower back, abdominals)
- Impaired ROM: tight heelcords (up on toes), hip flexors (weak abdominals), IT band (wide BOS)
20
Q
DMD - Characteristic Posture
A
- weakness in hip girdle and abdominals
- causes exaggerated lordosis
- COM moves forward
- to keep balance - come up on toes
- additional compensation for maintaining balance - arching
- loss of ROM in heelcords - weak anterior tibialis
21
Q
Gower’s Sign
A
- problem with hip girdle weakness
- from prone -> all 4’s -> walk hands up legs
22
Q
DMD - Transitional Phase
A
- Approximately age 6-12
- Onset of marked postural changes
- Significant weakness
- Significantly impaired gait/mobility
23
Q
Transitional Phase - Functional Limitations
A
- Difficulty walking
- Difficulty climbing stairs
- Unable to get up from floor
- Difficulty with supine to sit
- Difficulty with transfers
- Difficulty with self care activities
(order to occur: unable to get up from floor -> difficulty climbing stairs -> difficulty walking)
24
Q
Transitional Phase - Impairments
A
- Muscle Weakness: prox ms continue to weaken, more apparent; trunk-abdominals, back ext, neck flexors
- Impaired ROM: develop contractures (no matter what you do - strategy=delay)
- Impaired posture: COM shifts fwd, increase on toes, shoulders arched
