- Latin = split spine
- Defect in neurulation
- Unfused condition of vertebral arches with or without protrusio or dysplasia of the spinal cord or its membranes
Incidence
- About 3 per 1000 live births in Great Britain
- 1/200 live births in the US
- 1.4 / 1000 in Australia
- Spina bifida occulta seen in 25% of infants and 5% of adults
- If one child is affected, there is 5% chance of the next child being affected, increasing to 40% if two children affected
- Male : Female
- Female slightly greater
- Prenatal screening done in all pregnant woumen: elevated levels of serum alphafetoprotein: 75-80% sensitivity
Aetiology
- Unknown
- Great geographical variation in frequency
- Higher incidence in certain races
- Higher incidence in firstborn children
- Higher incidence in lower socioeconomic status
- Theories
- Recessive inheritance with less than 1:4 ratio due to early fetal loss (Lorber)
- Environmental factors (Von Reckllinghausen)
- Hamartomatous growth (Pattern)
- Association with:
- Low maternal dietary folate
- Maternal IDDM
- Maternal hyperthermia
- Valproic acid
Classification
- Spina bifida occulta : Incomplete closure of laminae without cystic distension of the meninges
- Spina bifida cystica
- Meningocele : cystic distension of the meninges, but no neurological loss (6% of cases)
- Myelomeningocele : cystic distension of the meninges associated with neurological loss (94%) usually of the lumbar or lumbo-sacral junction
Clinically
- Level: Defined by the lowest active motor root
- General Categories:
- Upper thoracic
- Lower thoracic
- Upper lumbar
- Lower lumbar
- Sacral
- Flaccid vs. Spastic paralysis
- Pts with L4 function have good chance for functional walking (household or community ambulators)
- Pts with L5 function have good chance of being community ambulators
- Spina bifida occulta (Spinal dysraphism)
- L5 / S1 and cervical axis most common
- Although the skin may be intact, it is almost never normal as some midline anomaly suggests the diagnosis
- Anomalies range from a tiny dimple or excess "down" to a large pigmented nevus or a veritable "faun's tail"
- A bulge deep to skin is suggestive of a lesion
- Neurological defect occurs in a very small percentage and will depend on level and extent of cord involvement
- Associated with spinal dysraphism, tethered cord syndrome and diastematomyelia
- Spina bifida cystica (Meningocoel or Myelomeningocoel)
- Posture may suggest paralysis and may indicate the neurological level
- Lower limb paralysis may be complete or incomplete, associated with urological problems
- 85% of children, regardless of their functional level, have some form of paralytic deformity of the foot
- Hip dislocation, genu recurvatum or flexion contracture may be evident
- Recurvatum may be a feature at the knee, associated with talipes and claw toes in the feet
- These deformities may develop following birth due to unbalanced paralysis, if not evident initially
- Scoliosis occurs in 80% of the thoracic and high lumbar lesions by adulthood and curves greater than 35° at 9 years will progress
- Anaesthetic skin may cause problems with pressure areas
- 90% of patietns have lower urinary tract dysfunction
- Historically this led to renal failure and high levels of mortality. New methods of urologic management have dramatically reduced morbidity and mortality secondary to urinary issues.
- Latex hypersensitivity in 3.8 - 6.6%
- due to exposure to latex from multiple surgical procedures, catheterization, etc...
- Symptoms include swelling or itching in areas with latex contact
- All patients should have all procedures done in latex-free environment
- 50% of spina bifida children have subluxated or dislocated hips by the age of 2 years
- Vertical talus is more often associated with myelomeningocele than as an isolated congenital deformity
- Other vertebral anomalies such as hemivertebrae, absent vertebrae and abnormal bars are not an uncommon (15 - 20%)
- Mental retardation in 30%
- Children with high neurosegmental levels have more developmental delay than a child with a low lesion
- Bone fragility is common and 20% develop pathological fractures
- Young children are often seen with upper limb weakness and spasticity due to Arnold Chiari malformation
- In older children syringomyelia may produce upper limb dysfunction
- A child that has scoliosis or deformity of rapidly increasing severity is neurologically unstable until proven otherwise (shunt malfunction, syringomyelia, Arnold Chiari malformation or tethered cord should be considered)
- Only 30% of all patients who have a myelomeningocele are functionally independent
- 29% lack control of bowel and bladder
- Lipomeningocele
- defect contains a lipoma that is intimately involved with sacral nerves
- Diastematomyelia
- Osseous cartilaginous, or fibrous septum in the central portion of the spinal canal that results in complete or incomplete sagittal division of the spinal cord into two hemicords.
- Upper lumbar levels commonly involved
- Females are affected more commonly than males.
- Tethered cord syndrome
- May recur after repair of myelomeningocele
- Incidence of retethering: 11-20%
- Occurs at 6-11 yeras of age
- Signes: back, buttock, or lower extremity pain, progressive motor deterioration, progressive foot deformities, rapid increase in severity of lordosis or scoliosis
- Dx: MRI with contrast
- Must also r/o associated dermoid cyst
- Tx: early release stops progression of spine deformity, relieves pain
- Hydrocephalus
- 90% of patients require VP shunt
- Should be monitored regularly by neurosurgery
- Acute hydrocephalus: bulging fontanelle, altered mental status, headache, N/V
- Syrinx may develop in setting of shunt failure resulting in progressive scoliosis, motor deterioration, pain
- Arnold-Chiari Malformation
- Seen in 95% of children with myelomeningocele
- Herniation of posterior fossa structures (e.g. cerebellum, brainstem) through foramen magnum
- leading cause of death in infants
- Sxs: intermittent apnea, stridor, nystagmus, weak cry, upper-extremity spasticity/weakness
- Some deformities persist/progress and require surgical decompression
X-Rays
- Gap in the neural arch
- Widening of the spinal canal is common
- A bony spur of diastematomyelia should be sought
- Bones are osteoporotic and spontaneous fracture is not uncommon
- May heal with excessive callus
- Other spinal deformities may be evident
- Unsegmented bars
- Hemivertebrae
- Fused ribs
- Scoliosis
- Lordosis
- Kyphosis
Pathology
- Failure of development of the neural tube from the neural plate at the 4 weeks stage in utero
- The two halves of the neural tube have failed to fuse and through this defect membranes or cord may protrude
- The cord itself may be undeveloped (dysplastic)
- Skin may be closed over the defect or the defect open to the environment
- Closed defects are associated with
- Dermal cysts
- Lipoma of the cauda equina
- Diastematomyelia (cord is bifurcated by bone projecting backwards from the vertebral body)
- Partial or complete absence of the sacrum and meningocele
- Meningocele is very rare and is merely a thecal hernia containing no neural elements
- Myelomeningocele is a meningeal sac containing nerve roots and cord remnants, which may be adherent to the sac and protrude through the bony defect
Investigations
- All patients with new-onset spasticity, rapidly progressive scoliosis, etc.. should be evaluated for cord tethering, hyromyelia, and shunt function
Treatment
- Require a team approach (neurosurgery, orthopaedics urology and paediatrics and the physiotherapist and splint maker)
- Above all, requires parental understanding and ceaseless devotion
- If closure of defect is indicated, should intervene within 48 hours (selection of patients ethically controversial)
- May elect not to treat, if the lesion is high and skull enlarged
- Surgery indicated for bladder dysfunction, tethered cord, hydrocephalus and subsequent deformity
- Forcible overcorrection and splinting is forbidden due to weak bones and skin paresis
- Surgical correction of deformities is preferred when the child is at least several months old
- If deformity of hip, knee and foot co-exist, correct hip then foot then the knee
- High complication rate of procedures (infection, pathological fractures and pseudarthrosis)
- Surgery to correct spine and limb deformities will be more rewarding when the child is neurologically stable and free of urinary tract infection
Treatment specific to regions
Hip
- Common at L3/L4 level
- Prime cause of hip instability is paralysis of the abductors and extensors with power remaining in the flexors and adductors in a mid-lumbar lesion
- Unilateral dislocation: open reduction; if dislocations are bilateral, some recommend managing conservitively (controversial)
- Open reduction, tenotomy or muscle transfer may be needed to reduce a dislocated hip
- Early correction avoids late bony changes
- Occasionally osteotomy or excision of the femoral head needed
- Aim for a hip stiff enough to support the standing weight in extension and flexible enough to allow sitting
- Iliopsoas transfer (Sharrard) : Pass tendon through a hole in pelvis to greater trochanter to redirect pull of flexors
Knee
- Patients often have quadriceps weakness requiring KAFO
- Correction of genu valgum needs release of contracted iliotibial band
- For correction of flexion deformity release hamstrings, if not corrected by fixing FFD of the hip. May need to extensively release knee structures or do extension osteotomy
- Genu recurvatum may be due to equinus of the foot
Tibia
- Torsional deformities secondary to muscle imbalance
- Tx: osteotomy
Foot
- Need plantigrade foot with adequate plantar skin which is suitable for bracing
- Perform soft tissue procedures usually at around 6 months
- Deformities include
- Equinus : posterior release
- Equinovarus (most common) : postero-medial release
- Calcaneus (strong tibialis anterior) : transfer its tendon to os calcis
- Valgus : tendon transfer or subtalar arthrodesis
- Cavus foot : plantar release, metatarsal +/- os calcis osteotomies
- Vertical talus
- Clubfoot: Most are rigid deformities requiring surgical correction
- Fixed deformity requires bony procedures, e.g. triple arthrodesis, Grice arthrodesis, Dwyer procedure
- Vertical talus is seen in children with thoracic and lumbar levels
Spine
Aim to maintain a stable posture for sitting
- Scoliosis
- Most common skeletal deformity in myelomeningocele
- Occurs in 80%
- Thoracic/upper lumbar levels incidence is 95%
- Lumbosacral level incidence is 40%
- Natural history is progression
- If progression is rapid, get an MRI to r/o tethered cord and neurosurg eval for shunt
- Causes
- Congenital spinal malformations
- Unequal growth
- Embryological causes
- Failure of formation
- Failure of segmentation
- Lead to a progressive, rigid scoliosis
- Mechanical instability due to absent\deficient posterior elements and to paralysis
- Neurologic abnormalities caused by hydromelia and tethered cord
- May be due to a malfunctoning shunt and if this is replaced the curve may spontaneously correct
- If due to tethered cord, release of tether prevents progression
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- High pseudoarthrosis rate
- Infection rate up to 25%
- Kyphosis
- Occurs in ~15% of patients with myelomeningocele
- Often severe with breathing and eating difficulty
- 2 types :
- Rigid type
- Apex ~ L1 - L2
- Associated with rigid lordosis in the proximal adjacent lower dorsal spine
- Treatment is excision of 1 or 2 vertebrae proximal to the apex
- Collapsing type
- Due to muscle weakness
- Can be corrected by manual pressure
- Not associated with proximal lordosis
- Aim to avoid surgery for as long as possible to allow for longitudinal spinal growth
- Need to exercise great care with use of braces
- Lordosis
- Excess lumbar lordosis often due to other problems, e.g. FFD of hips
- Tethered cord is more common in children with lesions at the 4th or 5th lumbar vertebrae than thoracic
- Development of scoliosis at a young age often indicates tethering
- Surgical Treatment:
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