Down Syndrome and Neural Tube Deficits

types of down syndrome

• Genetics

• 3 types of Down syndrome, depending on the chromosomal alteration

• Trisomy 21

  • 95% of the cases of Down Syndrome

• Translocation

  • 4% of the cases of Down Syndrome

• Mosaicism

  • 1% of the cases of Down Syndrome (may be less severe

etiology of down syndrome

Associated with increased maternal age

• Abnormal embryonic development

• Prenatal diagnosis possible with

  • amniocentesis

  • blood screenings

  • fetal ultrasound

incidence of down syndrome 

• Approximately 1 in 700 children

• Approximately 1 in 643 births

• Trisomy 21 is the most common 

rex and preus index – physical characteristics for diagnosis of Down syndrome

• Based on numerous characteristic features, a child can be diagnosed with Down Syndrome with 99.9% accuracy

  • Palm print pattern

  • Brushfield spots

  • Ear length (usually shorter)

  • Internipple distance (narrower)

  • Excess back neck skin

  • Widely spaced first toes

physical characteristics of Down syndrome

■ Simian crease

■ Smooth lip philtrum

■ Broad nose with a flat nasal bridge

■ Upward slanted eyes with epicanthal folds

■ Small mouth with a shallow roof

■ Tongue protrusion

■ Low-set ears

■ Fontanels are larger and will close later

■ Only one crease in the hand

■ Curved inward 5th digit

■ Thin, sparse, and soft hair

■ Round face, small head

■ Short stature

■ Short limbs

■ Only one crease in hand

■ Curved inward 5thdigit

■ Thin, sparse, and soft hair

■ Round face, small head  

other characteristics of down syndrome

• Hypotonia is common

• Delayed gross motor and speech milestones

• Common milestones are achieved later:

  • Sit at 11 months

  • Walk at 19 months

  • First word at 18 months

• Boys with Down syndrome are pubescent later than girls with Down syndrome

• A mild to moderate cognitive deficit is typical in people with Down syndrome

comorbidities associated with Down syndrome

• Congenital heart defecits

• Ophthalmic disorders

• Hearing loss

• Respiratory problems

• Endocrine abnormalities

• Skin conditions, eczema

• Obesity

• Orthopedic abnormalities

• Dental abnormalities

• Gastrointestinal malformations

• Epilepsy

• Leukemia

• Cognitive deficits

• Alzheimer’s dementia

prognosis of down syndrome

• Lifelong condition

• Life expectancy has increased to about 60 years of age and increasing (was 10 years of age in 1960!)

  • Black infants have a lower survival rate after the first year and indications of later diagnoses

• Prior to 2000s, people from minorities had half the life expectancy!

• Many individuals with Down Syndrome die due to heart defects (50%-65% have defects), dementia (50% of those over 50 y.o.), hypothyroidism, or leukemia

neural tube deficits 

A group of malformations of the spinal cord, brain, and vertebrae.

• 3 types of neural tube deficits (NTD)

  • Encephalocele

  • Anencephaly

  • Spina bifida

encephalocele

• A malformation of the skull that allows a portion of the brain to protrude.

• Occipital lobe location: hydrocephalus, spastic legs, and/or seizures

• Frontal lobe region: no abnormalities

anencephaly

• Severe congenital malformation of the skull and brain in which no neural development occurs above the brainstem.

• Fetuses are usually spontaneously aborted.

• Born babies usually don’t live past infancy

spina bifida

• Most common type of NTD

• Neural tube does not close

• There is a split in the vertebral arches (at any location)

• May occur with a protruding meningeal sac

• Sac may contain part of the spinal cord

• Children often have average IQ

• More spinal cord damage associated with greater risk of learning difficulties

etiology of neural tube deficits 

• The malformation occurs by 26 days after fertilization of the egg.

• This happens when the neural groove does not completely close, and the spinal cord becomes malformed.

• Environmental and genetic factors are causes of NTDs

• foloc acid reduces the risk of borth defects and the FDA requires thst balers include it in enriched bread

• Increased risk of having an offspring with NTD for mothers 40 years or older — stronger for spina bifida than for ancephaly

• Mothers 19 years old or younger have higher risk for having a child with spina bifida

risk factors for spina bifida

• Pregnant people not getting enough folic acid daily BEFORE and DURING pregnancy

• Certain medications

• Diabetes that is not well-controlled

• Overheating (hot tub) or fever in early weeks of pregnancy

• More common among Hispanics and Whites

• Valproic acid to control seizures

• Pre-pregnancy obesity

• Genetics

spina bifida occulta

• Most common spina bifida

• Only a small gap in the spine

• A visible abnormality on the lower back

• A reddish birthmark known as a hemangioma or flame nevus

• Tuft of hair

• Dermal sinus

• Small lump- lipoma

• May not be diagnosed until adulthood, maybe never!

• Usually no deficits

meningocele

• An exposed membranous fluid-filled sac covering the spinal cord- meningocele

• The spinal cord is not pinched

• Few to no symptoms are present

• Potential for minor disabilities

meningomyelocele 

• Most complex congenital malformation

• A sac is present and may not be closed, with the spinal cord protruding into it and being malformed.

• Non-progressive condition

• Symptoms include:

  • Paralysis

  • Sensory loss below the lesion of the spinal abnormality

  • Hydrocephalus

  • Abnormal migration of neurons

  • Limitations in LE movement

  • Moderate to severe disabilities

prevalence of NTD 

• Varies with genetic and environmental factors

  • Children with NTD more likely to have a child with NTD

• Females are 3 to 7 times more likely to have a NTD than males

• Folic acid supplementation has greatly decreased the incidence rate

• Survival rate is higher with medical advances

• spina bifida without ancephaly is most prevalent — then encephalocele, anencephaly

diagnoses before birth 

in utero surgery to close the spinal column before 26 weeks gestation 

• improved motor function 

• decreased risk of death in infancy due to spina bifida 

• decreased need for shunting after the first year 

• risks 

chiari malformation

• With myelomeningocele - the brainstem and part of the cerebellum are pulled downward protruding through the magna foramen of the skull.

• Signs include arm weakness, difficulty swallowing, choking, hoarseness, breath-holding spells, apnea, stiffness in arms, and holding the head in an arched back position (called opisthotonos).

• Can be treated surgically to decrease the pressure on the brainstem

characteristics of meningomyelocele

• Mobility impairments

• Cognitive impairments

• Seizure disorders

• Fine motor impairments

• Visual impairment

• Musculoskeletal abnormalities

• Urinary and bowel dysfunction

• Pressure ulcers

• Weight and stature abnormalities

• Psychosocial issues

• Contractures

adulthood with NTD 

• 85% of children survive into adulthood due to an increase in successful methods of shunt use (and revision) and other advanced medical services.

• Continued care and maintenance of deficits is necessary through adulthood to avoid loss of function and independence