Chapter 131 - Pediatric Neuromuscular Disorders

Question 1

botox mechanism of action

Answer 1

irreversibly binding to synaptic proteins at the NMJ to block pre-synaptic release of acetylcholine

Question 2

is Botox FDA approved??

Answer 2

only for adults in upper extremity spasticity
used off label in kids with CP

Question 3

hip flexor contractures can lead to what spine manifestation

Answer 3

hyperlordosis -> spondylolisthesis

Question 4

cp patients < 5th percentile for weight carry what risks?

Answer 4

post operative spinal fusion complicaitons
- hardware failure
- infection
- pulm complications
- GI complications

Question 5

curves exceeding 90 degrees require what?

Answer 5

anterior release with posterior fusion (one or two stage procedure)

Question 6

outcomes of surgically treated scoli in cp

Answer 6

increase in quality of life - sitting balance, cosmesis, care giver satisfaction, lifespan

NO functional gains/benefits

Question 7

how does hip subluxation differ from DDH

Answer 7

POSTEROSUPERIOR dislocation
2/2 spasticity of adductor, iliopsoas tendons
(obturator n predomintely)
will develop in 50% of quadriplegics (less common in ambulatory kids)

Question 8

how to surgically treat CP hip dislocation?

Answer 8

age <8, <60%subluxation: addutor, gracilis tenotomy (add IP tenotomy if hip flexion contracture >20deg)

age <8, >60% subluxation: valgus derotation osteotomy

Age >8, >40% subluxation get VDRO and/or pelvic osteotomy (dega or albee)

Closed triradiates - chiari osteotomy

Question 9

how to treat scissoring in CP

Answer 9

• adductor contracture
• proximal adductor release

DO NOT do obturator neurotomy

Question 10

grouched gait is a result of what?

Answer 10

spastic or contracted hamstrings

less commonly from too much dorsiflexion in the ankle of ankle equinus

Question 11

risk factors for myelomeningocele

Answer 11

previously affected pregnancy
low folic acid intake
pre-gestational maternal diabetes
in utero exposure to valproic acid or carbamazepine

Question 12

what is the distal most level that can be affected in myelomeningocele and still allow community ambulation

Answer 12

L3

Need L4 for quadriceps control

Question 13

what to do for kids with dislocated hip and myelomeningocele

Answer 13

nothing
leave a dislocated hip alone
high risk of recurrence

Question 14

child or SCI patient with a red hot swollen leg has what until proven otherwise?

Answer 14

fracture

Question 15

x lined recessive gene defect is where?

Answer 15

patients mother’s paternal side - usually new mutations in spermatogenesis

Question 16

duchenne muscular dystrophy

Answer 16

X Linked recessive

skeletal and cardiac muscle

1:3500 males

Xp21.2 (point deletion - nonsense mutation) - DYSTROPHIN - stabilizes the muscle cell membrane is ABSENT

Question 17

Presentation of DMD

Answer 17

between age 3-6, toe walking, flatfootedness, cant run or climb stairs, calf pseudohypertrophy, gowers sign (use UE to get off floor)

affects PROXIMAL muscles > distal muscles

Elevated CPK

Question 18

medical treatment for DMD

Answer 18

corticosteroid - emflaza/deflazacort

decreased the need for scoliosis fusion (from 92-> 20%), slows deterioration of forced vital capacity

side effects are all those associated with long term corticosteroids

Question 19

effects of night time ventilation for DMD patients

Answer 19

substantially prolongs survival

Question 20

dont brace DMD scoli

Answer 20

ineffective and not recommended

early fusion for curves >20 is recommended to preserve forced vital capacity

!!! DMD patients are at risk for malignant hyperthermia - avoid inhalational anesthetics and succinylcholine

Question 21

Spinal Muscular Atrophy genetics

Answer 21

Autosomal recessive

1:10000 children

Question 22

phenotype for SMA

Answer 22

progressive weakness that starts proximally and moves distally thru the body

SMAI: onset at birth, severe spinal manifestations, death by age II

SMA II: onset 6-18 months, weakness worse in LE, hip dislocation common, life expectancy 15+ yr

SMA III: onset >18mo, stand independently at first, but wheelchair bound as adults, more proximal weakness, normal life expectancy

SMA IV: onset in adulthood, moderate proximal mm weakness

Question 23

genetic defect in SMA

Answer 23

survival motor neuron chromosome 5 mutation

result in progressive alpha motor neuron loss in the anterior horn of the spinal cord with associated progressive weakness

Question 24

Charcot marie tooth most common inheritance pattern and most common genetic defect

Answer 24

autosomal dominant most common

PMP-22 - peripheral myelin protein 22 on chromosome 17 most common mutation

x-lined connexin 32 mutation also common

Question 25

CMT phenotype

Answer 25

CMT is a very common cause of peditric cavus foot diagnosed before age 10

cavus foot, claw toes, foot drop

foot affected first, then hands, and tongue
increased incidence of scoli and hip dysplasia

DISTAL muscle weakness

Question 26

Hip pathology in CMT

Answer 26

hip dysplasia ALWAYS requires treatment in CMT
- acetabular reconstruction favored over VDRO

Question 27

pathophysiology behind the cavus foot in CMT

Answer 27

weak tib ant causes equinus.
weak peroneus brevis causes heel varus

strong peroneus longus causes plantar flexion of the first ray, planus

contracted platar fascia contributes to pes planus
normal fhl.fdl cause clawing

Question 28

flexible cavovarus in CMT

Answer 28

plantar fascia release
peroneus longus to brevis rtansfer
ehl transfer to the first MT head
proximal first MT closing wedge osteotomy
tib ant transfer

Question 29

fixed cavovarus CMT

Answer 29

calcaneal osteotomy

Question 30

friedrich’s ataxia

Answer 30

most common form of the uncommon spinocerebral degenerative diseases

three nucleotide repeat accumulation GAA

FRATAXIN gene on chromosome 9q13

results in loss of the protein frataxin -> normally responsible for cellular IRON hemostasis

glute max involvement first, severe scoli and cavovarus foot, ataxia, areflexia

assoc with hypertrophic cardiomyopathy, diabetes, hearing or vision loss

Question 31

Rett syndrome

Answer 31

X linked dominant - LETHAL in affected male fetus’
most often denovo mutation
impaired DNA methylation