Spina Bifida

Definition

  • Congenital disorder in which the 2 halves of the posterior vertebral arch (or several arches) fail to fuse
  • Anencephaly = cranial end equivalent
  • Multiple organ involvement due to abnormal innervation of structures supplied by affected part of nerve

Demographics

  • Isolated laminar defects are seen in 5% of lumbar spine Xrays
  • <1 per 1000 live births in Australia
  • up to 5 per 1000 in some countries
  • If one child is affected then there is a 10 fold risk for the next child

Aetiology

  • Dysraphism
    • Embyonic defect associated with maldevelopment of the neural tube & the overlying skin
  • Environmental implications
    • Folate deficiency
    • Selenium deficiency in soil
    • Maternal alchohol
    • Maternal diabetes
    • Fever at critical antenatal stage
  • Usually occurs in the lumbar or lumbosacral region
  • With neural involvement there can be motor, sensory & autonomic dysfunction

Pathology

Spina Bifida Cystica

  • Severe dysraphism with absent laminae & prolapse of the theca ± its contents
  • Visible Cyst Present
  • Meningocoele
    • CSF filled sac through the defect
    • Cord & roots still confined within vertebral arches
  • Myelomeningocoele
    • Cyst including cord/ cauda/ nerve roots prolapsing
    • Cyst lined by dura & arachnoid
    • Commonest form
  • Racischisis
    • Open Myelomeningocoele
    • If the cord is still in its primitve state (ie. unfolded)
    • neural plate forms the roof of the prolapsing sac
  • Closed Myelomening
    • If the neural tube is formed the roof of the sac is formed by dural membrane

Spina Bifida Occulta

  • Midline laminal defect without prolapsing neural tissue
  • Hidden defec
  • There can be associated intraspinal defects
    • Tethering of the conus
    • Diastomatomyelia
    • Cysts or lipomata of the cauda
  • There may be skin signs of this with a dimple, a pit, or a tuft of hair

Multisystem Involvement

Hydrocephalus
  • ~ 72%
  • Secondary to Arnold Chiari malformation ± tethering of the cord
    • brainstem may be dragged distally, herniating through the foramen magnum
    • obstructing outflow of CSF
  • If untreated it will lead to cerebral atrophy & retardation
Neurological Deficit
  • Myelomeningocoele is always associated with neurological changes at & below level of the lesion
  • Even with occulta there can be neurology
  • Many patients have upper limb neurology because of subtle neurological lesions
Visceral
  • Bowel & bladder paralysis
  • Tendency to trophic ulceration of sacral / buttock / feet skin

C>Clinical features

  • Assess early for level of lesion & annual full neuro check
  • Clinical assessment of level of lesion is easier after 5 y.o.

Spina Bifida Occulta

  • If there are skin signs then neurological deficit is more common
  • May present at any age
  • Usually partial cauda equina symptoms with bladder symptoms along with motor & sensory features

Spina bifida Cystica

  • Obvious saccular lesion at birth, that may have skin or just membrane covering
  • An open myelomeningocoele will have neural elements merging with plum coloured skin around
  • the perifery
  • head may be enlarged with widened sutures due to hydrocephalus
  • posture may suggest the neurological level
  • associated abnormalities;
    • hip dislocation
    • genu recurvatum
    • CTEV
    • Claw toes
      • Such deformities may be due to muscle imbalance or foetal positioning
  • Neurological deficit;
    • Is complete in a third
    • Is complete at the level but there is some distal preservation in a third
    • Is incomplete in a third
  • 60% have upper limb neurological deficits (often require both hands free to perform simple tasks)
  • Walking
    • Thoracic – Most will not walk into adult life
    • Lumbar – May continue walking if strong quads & no significant hip deformity
    • Sacral – Useful walkers, often without orthoses in adult life
  • Children with L-1 & L-2 neurosegmental levels are rarely community ambulators as adolescents
    • but time spent walking in braces may be longer than in children with thoracic lesions
    • so surgery to improve brace fitting should be considered
  • Children with L-3, L-4, & L-5 neurosegmental levels with strong quads are usually good walkers.
    • They usually require an ankle-foot orthosis to stabilize the ankle
    • need for crutches or walking aids depends on the strength of abductors at hip
  • Most children with sacral lesions are effective community ambulators until adulthood,
    • when some deteriorate & cease walking. Hip deformity is uncommon
    • but surgery is often necessary for foot & toe deformities

Inves>Investigations

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  • Genetic counseling
    • One affected » 1 in 25 risk for subsequent babies for neural tube deficits
    • Two affected » 1 in 10 risk
    • Three affected » 1 in 4 risk
  • Screening using
    • Maternal Alphafetoprotein levels in serum
      • 16th to 20th week
      • If high, then need USS ± amniocentesis for Diagnosis
    • Ultrasound
      • detects most anencephalics by 10 – 12 weeks on PV USS
      • detects most by 16 – 18 weeks on standard abdo USS
      • detects > 80% of spina bifida on standard USS at 18 weeks
    • Amniocentesis
      • Alphafetoprotein levels
      • May still miss small skin-covered defects
  • XR
    • Midline bony defect
    • Associated bony anomalies
      • Unsegmented bars
      • Hemivertebrae
      • Fused rib s
    • All of these can lead to abnormal curves
  • MRI
    • To visualise the cord & the lesion
    • Brainstem herniation
    • Diastomatomyelia
    • Syringomyelia
    • Cysts/lipomata in the theca

    • PreventionPrevention

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  • Folate / multivitamins
  • Some elect for antenatal Diagnosis » abortion
  • If detected NTD » consider elective LUSCS at 36 weeks (less severe neurological defects than NVD at term)

    • Treatment

    >Treatmentp-block-list">
  • Multidisciplinary in large centre
    • Coordinator, neurosurgeon, orthopaedic, urologist, paediatric surgeon, psych, social worker, physio, orthotist, stomal, school aids etc
  • For the focal deformity:
    • Closure of skin over the defect within 48 hours
  • For the hydrocephalus:
    • Venticulocaval shunt
  • For the urogenital abnormalities:
    • Permanent catheter or a diversionary procedure
  • For the musculoskeletal problems:
    • 2 important things to remember:
      • the bones are weak – therefore forceful corrections may lead to Fracture
      • the skin is insensate – therefore splinting must avoid pressure areas, & plasters are to be avoided
    • Postoperative heterotopic calcification around hip may be problematic if high lesions

    • Abnormalities &>Abnormalities & their management by region

    ock-heading">Spine
    • Combination curves are common & can be severe
    • Braces may slow the progression but many require surgical correction
    • Kyphosis
      • If present at birth » usually associated with hydrocephalus
      • Usually lumbar
      • Increase > 8o per year
      • Correct if skin integrity compromised
    • Scoliosis
      • Most = paralytic (some are congenital or mixed)
      • Most common in thoracic lesions
      • Brace only for those with rapidly progressing curves & too young for surgery
      • Indications for surgery
        • Stable posture for standing & sitting
        • Aim for level pelvis & trunk vertical on this
        • Try to avoid need for hand support for sitting
        • For stable fusion & prevent recurrence
        • Skin integrity
        • Respiratory function
      • Most surgical corrections = >35o & 8 – 14 y.o

    Hip

    • 3 problems
      • Deformity
      • Dislocation
      • Weakness (extension & abduction)
    • Aim
      • enable the child to stand straight in calipers & also to be able to sit in a chair
    • Flexion
      • Commonest deformity
      • <20° & good walking potential » observe
      • >20° & good walking potential » soft tissue release anterior & lateral
    • Dislocation
      • Reduction of dislocated hip does not improve walking potential
      • May reduce to correct leg length discrepancy
      • Usually associated with pelvic osteotomy to maintain reduction
    • Weakness
      • Above L1
        • then all the muscles are flail
        • splintage is all that is required
      • Below L5
        • deformity is one of flexion
        • either a flexor muscle ‘slide’ on the ilium or a psoas tendon elongation can be performed
      • Usually the lesion is between these levels
        • imbalance leads to hip subluxation
        • 50% of SB kids have subluxated or dislocated hips by the age of 2!
      • In view of the dangers of splinting & plasters
        • it is important to achieve muscle balance
        • psoas tendon transfer from lesser to greater trochanter achieves this
        • by decreasing flexor strength & increasing abduction & extensor strength
        • (Sharrard advocates passing the tendon through a hole created in the ilium)
        • (Mustard prefers to pass the muscle in front of the bone)
      • As the child gets older it becomes more difficult to reduce the hip
      • If the child is functionally OK then it is better to observe

    Knee

    • Aim
      • knee that can be held straight in a caliper, & can also be flexed to sit in a chair
    • Recurvatum can be treated with a careful quadriceps elongation
    • Undeformed knee with Quads weakness = common
    • Fixed Flexion
      • Common with thoracic lesion
        • < 20° can be observed
        • >20° = if walker » posterior hamstring release ± capsular release
    • Recurvatum
      • Problematic > 6y.o
      • Subcutaneous tenotomy of patella tendon

    Tibia

    • External torsion
      • Often with ankle valgus
      • Perform supramalleolar derotation osteotomy after 8y.o
    • Internal torsion
      • < 3 y.o. can perform osteoclasis of tibia & fibula
      • Later stage = supramalleolar derotation osteotomy

    Foot

    • The aim is a plantargrade foot
    • May be worth correcting deformity in non-walkers to look normal & wear normal shoes
    • Varus
      • Results in weight bearing on outer border of foot
      • Surgical correction
    • Valgus
      • Need to determine if mortise or STJ origin
        • Ankle
          • Distal end of fibula more proximal than normal
          • XR = growth plate more proximal than mortise
          • Lower tibial physis is wedge-shaped
          • Correct during growth by parital epipyhyseodesis of tibial growth plate
          • (Staples, Phemister, Closed drilling)
          • Correct at later age by supramalleolar osteotomy
        • STJ
          • Usually controllable with footwear & orthoses until adolescence
          • Os calcis osteotomy (medial based wedge + medial translation)
          • STJ valgus often accompanied by external torsion & valgus of ankle mortise
          • Consider Grice extra-articular subtalar fusion or triple arthrodesis
    • Equinovarus
      • May be anything from mobile to stif +++
      • Early casting with regular changes
      • Closed TAL
      • PMR may be required for CTEV at age 6 months
      • If recurrent deformity » consider later triple arthrodesis
    • Equinus
      • Closed or open TAL
    • Cavus
      • Minor deformity » division of tight plantar tissues
      • After 4 y.o. & heel varus » Os calcis osteotomy
      • At skeletal maturity » Consider triple arthrodesis
    • Calcaenus
      • Tib anterior transfer through interosseous membrane to heel
      • If fixed deformity » anterior ankle release ± TA tenodesis
      • If late deformity & “pistol grip” heel » Osteotomy of os calcis
    • Vertical talus
      • Paralytic Convex Pes Valgus
      • < 2 %
      • Should be reduced operatively at age 3 years
      • to avoid a boatshaped foot with the potential for plantar ulceration
      • Cincinati
    • For claw toes flexor to extensor transfers can be performed for the outer 4 toes
    • For the great toe FHL tenodesis (to the base of the proximal phalanx) is preferable

    Prognosis

      <>Prognosiseve independent walking, two thirds use a wheelchair