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Clinical Medicine III > Neural Tube Defects & Muscular Dystrophies > Flashcards

Neural Tube Defects & Muscular Dystrophies Flashcards

1
Q

Congenital neural tube defects

A
  • combination of spinal canal deformities resulting from failure of neural tube closure during development
  • normally the spinal cord, cauda equina, and the protective meninges are enclosed inside the bony vertebral canal which happens with neural tube closure during fetal development
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2
Q

Describe neural tube closure during development

A
  • neural plate on dorsal side of fetus
  • neural groove by 20 days
  • neural tube: bottom end closes by day 27
  • lumbosacral area is the last to close
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3
Q

3 types of neural tube disorders (NTDs)

A
  • Spina Bifida Occulta (mildest form)
  • Meningocele
  • Myelomeningcele
  • generally occur ion lumbosacral level
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4
Q

Incidence and etiology of NTDs (neural tube disorders)

A
  • Overall incidence is declining due to improved maternal screening (MSAFP), better nutrition, use of prenatal vitamins containing Folic acid (Vitamin B9)
  • Etiology of NTDs is multifactorial: genetic predisposition, teratogenic exposure, & folic acid deficiency
  • Teratogens that are linked to increased rates of NTDs: valproic acid, lead, herbicides, solvents, alcohol, etc
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5
Q

Pathogensis of NTDs (neural tube disorders)

A
  • neural groove created by cell proliferation & production of hyaluronic acid extracellular matrix
  • 4 reasons for failure to close: (1) abnormalities in hyaluronic matrix; (2) abnormal overgrowth at caudal end; (3) abnormal production of surface ectoderm glycoproteins (act as glue holding cells together); (4) rupture of neural tube after closure due to CSF pressure
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6
Q

Loss of motor function is evenly distributed over the limbs & spine True/False

A
  • False: so muscle imbalance and scoliosis and contractures can occur
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7
Q

Clinical manifestations of Spina Bifida Occulta

A
  • doesn’t protrude visibly
  • depression/dimple on skin
  • tuft of hair present
  • soft fatty deposits underlying the skin
  • no neurologic dysfunction
  • occasional bladder/bowel disturbances & foot weakness
  • Meningocele manifestations are similar
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8
Q

Clinical manifestations of Myelomeningocele

A
  • permanent neurologic impairment
  • typically flaccid (LMN) paralysis, less often spastic
  • truncal hypotonia & delayed postural reactions during 1-2 yrs
  • absence of DTRs
  • sensory impairment below lesion level, loss of pain & touch
  • Musculoskeletal deformities: scoliosis, hip dysplasia/dislocation, hip/knee contractures, clubfoot, talipes valgus (vertical talus)
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9
Q

Define hydrocephalus

A
  • associated with Myelomeningocele
  • increased CSF pressure in the brain possibly due to blockage of CSF flow or after surgery closure of myelomeningcele
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10
Q

Signs and symptoms of hydrocephalus

A
  • bulging soft spot on top of child’s head
  • enlargement of head
  • large prominent veins on scalp
  • setting sun sign (always looking down)
  • seizures
  • vomiting
  • nausea
  • irritability
  • sleepiness
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11
Q

Describe Arnold-Chiari type I/II malformations

A
  • associated with Myelomeningcele
  • Type I: cerebellar tonsils extend down through foramen magnum
  • Type II: both cerebellum & brain stem extend down
  • Symptoms: weakness, vertigo, ataxia, diplopia, pain
  • can cause hydrocephalus
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12
Q

Describe tethered cord syndrome

A
  • associated with myelomeningcele
  • common following surgical closure
  • spinal cord becomes ‘tethered’ or bound down resulting in progressive neurologic impairments like weakness, pain, and incontinence
  • could cause Arnold-Chiari malformations leading to hydrocephalus
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13
Q

Describe bladder and bowel incontinence

A
  • associated with myelomeningcele
  • always present
  • either small spastic bladder (hold little urine) and urge incontinence (ureteral reflux) or large flaccid bladder (residual urine) and overflow incontinence (infections)
  • can have dyssynergistic bladder (problems with emptying/ureteral reflux)
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14
Q

Describe syringomyelia

A
  • associated with myelomeningcele
  • fluid filled cavity or ‘syrinx’ present within spinal cord or brain stem
  • Symptoms: sleep apnea, choking, may require mechanical ventilation, can be fatal
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15
Q

Diagnosis of myelomeningcele

A
  • Prenatally using US scanning, AFP testing, fetal MRI, Amniocentesis can only detect open NTDs
  • Postnatally: obvious on exam, differential diagnosis by transillumination (light shines through for meningocele but not myelomeningcele
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16
Q

Surgical treatment of myelomeningcele

A
  • Sac closure: timing of sac closure is important
  • Prenatal surgical repair: improves ambulation ability, decreases incidence of hydrocephalus & Arnold-Chiari malformations but has risk of premature birth, infection, tethered cord syndrome
  • Postnatal closure: needs to be within 48hrs
  • Ventriculoperitoneal shunt might be required to prevent hydrocephalus (unilateral valve prevents back flow)
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17
Q

Orthopedic corrective surges for myelomeningcele

A
  • to improve postural alignment throughout growing yrs
  • muscle releases to address hip/knee flexion contractures
  • soft tissue or bony procedures to correct foot deformities
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18
Q

Describe bladder/bowel management for myelomeningcele

A
  • Spastic bladder: complete bladder emptying using clean intermittent catheterization to prevent high pressures
  • Anticholinergic drugs to decrease high pressure & increase capacity
  • Bladder augmentation for increased pressure
  • Artificial urinary sphincters to manage urine outflow
  • Antibiotics to manage infections in flaccid bladder
  • Renal problems can cause significant morbidity & mortality & needs continuous monitoring
  • modifying diet and timed enemas
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19
Q

Describe the prognosis of myelomeningcele

A
  • early aggressive care improves prognosis
  • survival to adulthood is 85% with most deaths before 4
    -poorest prognosis in cases of total paralysis below lesion, kyphoscsliosis, hydrocephalus, progressive loss of renal function
  • if child is able to ambulate or use a w/c outdoors by age 7 = good prognosis if not by age 9 then ambulation might not happen
  • ambulation status declines with age due to increasing body size, loss of LE/UE strength, immobilization for extended periods of times due to surgeries
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20
Q

Implications for therapists for myelomeningcele

A
  • work with pt throughout life span providing direct interventions: proper positioning, skin ulcers during pre/post operative care, preventing complications like contractures, providing adaptive equipment to maintain/prolong functional status & educate family
21
Q

Care for myelomeningcele in NICU

A
  • pressure in sac must be avoided
  • prone positioning is optimal, allows hip extension and maintains neutral foot position with legs abducted
  • can be sidelying for position changes & to facilitate feeding
  • careful handling needed with hydrocephalus: avoid pressure & stretch to shunt, avoid head down positions
22
Q

Skin care foe myelomeningcele

A
  • proper positioning & padding to avoid skin breakdown when sensory/motor is involved
  • gentle massage can help with circulation
  • check skin daily for red areas
  • check bath water temp.
  • avoid latex gloves as they tend to be allergic
23
Q

Passive ROM & stretching for myelomeningcele

A
  • should be performed carefully
  • hip flexion/adduction may aggravate hip subluxation
24
Q

Therapy program for best outcomes for myelomeningcele

A
  • emphasize upright activities & ambulation show better outcomes
25
Q

Describe muscular dystrophies

A
  • largest/most common group of inherited progressive neuromuscular disorders
  • characterized by symmetric progressive muscle wasting with increasing deformities & disabilities
26
Q

Types of muscular dystrophies

A
  • Duchenne MD
  • Becker MD
  • Limb-girdle MD
  • Congenital MD
  • Facioscapulohumeral MD
  • Myotonic Dystrophy
  • all primarily present with degeneration of muscle
27
Q

Duchenne MD (DMD) and Becker MD (BMD) etiology

A
  • most common type is DMD
  • DMD is x-linked recessive disorders
  • predominantly males affected and females mostly carriers
  • signs/symptoms apparent by 2-4yrs, rapidly progressive, death in 20s
  • BMD: slowly progressive, lifespan til adulthood
28
Q

Limb Girdle MD (LGMD) etiology

A
  • has many subtypes
  • LGMD type 1: autosomal dominant
  • LGMD type 2: autosomal recessive & more common than type 1
  • onset in late childhood to early adolescence
  • slowly progressive & milder presentation
29
Q

Congenital MD etiology

A
  • onset of symptoms at birth or shortly afterwards
  • mostly autosomal recessively inherited
  • severity & rate of progression varies, some die in first yrs, others can live longer & achieve ambulation
30
Q

Facio-Scapulo-Humeral MD etiology

A
  • autosomal dominant
  • son or daughter of affected person has 50% chance of inheriting the defective gene
  • males affected more than females
  • early adolescence onset, slowly progressive, lifespan varies
31
Q

Myotonic Dystrophy etiology

A
  • 1/550 in isolated geographic populations due to ‘local founders effect’ (lack of genetic variation, genes of the ‘founders’ start appearing more frequently
  • subsequent generation shows more severe clinical presentation due to autosomal dominant inheritance & the phenomenon of ‘anticipation’ (enlargement in size of a triple repeat genetic code)
32
Q

Duchenne MD (DMD) and Becker MD (BMD) pathology

A
  • caused by mutation of the dystrophin dystrophin glycoprotein transmembrane complex) gene Xp21
  • Dystrophin links muscle membrane (sarcolemma) to the contractile proteins (actin/myosin)
33
Q

What happens when their is a lack of dystrophin

A
  • lack of dystrophin leads to disruption of sarcolemma during contraction relaxation cycles, uncontrolled influx of Ca2+ which triggers destruction of the muscle cell
  • inflammatory process initiates muscle necrosis/apoptosis, favors production of fibroblasts & adipose tissue
  • muscle is replaced by fatty connective tissue & contractures develop
34
Q

Difference between DMD and BMD

A
  • DMD: males with undetectable levels of dystrophin, lose ambulation before 13yrs
  • BMD: males with abnormal or lower levels of dystrophin, able to walk past age 16
  • can also be determined by age at which they lose ambulation capacity
  • Intermediate MD: those who walk past age 12 and lose the ability by 15
35
Q

Limb Gridle MD pathogenesis

A
  • can lead to damage to the proteins in the muscle which can to complications/defects such as sarcoglycanopathies & dystroglycanopathies
36
Q

Congenital MD pathogenesis

A
  • WWS (Walker Warburg Syndrome): most severe form of CMD, result from severe defects in POMT1 or POMT2 glycosylation enzymes
  • MEB (Muscle eye brain disease): result from severe defect in POMGnT1
  • Fukuyama CMD: severe defects in Fukutin, common DMDs in Japanese population
  • Ullrich CMD: result of defect in extracellular matrix protein collagen VI, more common CMD
37
Q

Facio-Scapulo-Humeral MD pathogenesis

A
  • occurs due to expression of a protein not naturally present
  • presence of reduced number of repeats produces a protein called double home box protein 4 (DUX4) which is normally not present
38
Q

Myotonic Dystrophy pathogenesis

A
  • defect due to the phenomenon of anticipation (increasingly larger number trinucleotide repeats ion subsequent generations), cytosine, thymine, & guanine are repeated abnormally large number of times
  • defective expression of protein kinase enzyme which affects chloride channels in membrane, insulin receptors and protein tau
  • Chloride channel: myotonia; Insulin receptor: risk of diabetes; Microtubule associated protein tau: cognitive delay
  • muscle fibers show altered resting membrane potential due to deregulation of ion channels
39
Q

Clinical manifestations of Duchenne MD (DMD)

A
  • effects muscles of shoulder girdle, rectus abdominis, pelvic girdle, by age 2-4 yrs & later hamstrings & calf muscles
  • Gower’s sign: walking up the legs using hands until weight of trunk is posterior to hip joint
  • Increased lumbar lordosis in standing to compensate for weak abs & hip extensors
  • Pseudohypertrophy of calf muscles, toe walking, & Trendelenburg’s sign
  • Scapular winging
  • Can’t use crutches due to shoulder weakness & increased lordosis
  • Loses ability to walk by 7-9 yrs
  • eventually become w/c bound
  • respiratory muscles get affected & increases risk for respiratory infections
  • cardiac muscles become affected
  • Common causes of mortality are respiratory, cardiac, or GI failure
40
Q

Clinical manifestations of Becker MD (BMD)

A
  • pattern resembles DMD but show later onset, slow progression, longer life expectancy
  • ambulation preserved till adolescence or later, toe walking
  • muscle cramps common in late childhood
  • scoliosis, UE/LE contractures, & other comorbidities found in DMD are also present but less severe
41
Q

Clinical manifestations of Limb Girdle MD (LGMD)

A
  • later onset, slow progression, first noticed in adolescence to adulthood
  • affects proximal shoulder & pelvic girdle
  • Scapular winging, lumbar lordosis, abdominal protrusion, waddling gait, poor balance, inability to raise arms up
  • ambulation capacity varies widely depending on the type of LGMD
42
Q

Clinical manifestations of Congenital MD (CMD)

A
  • more severe
  • symptoms typically present at birth, rapid loss of muscle strength & progressive respiratory Sx
  • WWS (Walker Warburg Syndrome): most severe CMD, present at birth, rapid progression, death usually prior to 1 yr, ocular impairments, brain abnormalities
  • MEB (muscle eye brain) disease: similar findings as WWS but wider variations, retinal abnormalities, glaucoma, polymicrogyria, cerebellar abnormalities
  • Fukuyama CMD: onset near birth, progressive weakness & contractures, typical loss of ambulation by 10yrs
43
Q

Clinical manifestations of Facio-Scapulo-Humeral MD (FSHD)

A
  • mild MD
  • onset around 2nd decade
  • inability to close eyes (possible 1st sign), facial flattening, pouting lower lip
  • scapular winging, difficulty raising arms overhead
  • most have normal lifespan
44
Q

Clinical manifestations of myotonic dystrophy (MD)

A
  • presents with muscle weakness, wasting, & myotonia (delayed relaxation of muscle following contraction)
  • ocular cataracts
  • cardiac conduction deficits may be serious comorbidity
  • severity based on the size of the genetic triple repeats
45
Q

Diagnosis of MDs

A
  • based on clinical presentation, family hx, genetic testing, EMG, muscle US or MRI, serum enzyme levels
  • EMG studies show fibrillation potentials, “dive-bomber” kind of sound typical in myotonia MD
  • muscle biopsy shows centrally placed nuclei, fat/connective tissue deposits
  • serum creatinine kinases levels may be high (sign of active muscle breakdown)
46
Q

Treatment of MDs

A
  • no known tx that stops progression
  • use of prednisone in DMD/BMD may delay progression & allow child to walk more yrs
  • corticosteroids could decrease progression of scoliosis
  • may require spinal fusion when scoliosis approaches 40º
  • stem cell & gene therapy are under investigation
47
Q

Prognosis of MDs

A
  • depends on type of MD
  • respiratory muscle dysfunction, cardiac muscle conduction defects are common sources of morbidity & mortality
  • DMD/BMD, CMD are more severe with shorter life spans
  • people with FSHD & LGMD can expect relatively normal life spans
48
Q

Implications for physical therapy

A
  • Tx focused on maintaining function for as long as possible
  • Contracture management (splinting, stretching, serial casting)
  • Encourage activity as much as possible specially with milder types of MD
  • Muscle strengthening specially high intensity eccentric type, might be contraindicated
  • Breathing exercise would be encouraged
  • Later stages might require airway clearance techniques like postural drainage & percussion to prevent complications

Clinical Medicine III (20 decks)

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