Definition
1. Spinal dysraphism
Failure of the neural tube to close (i.e. spina bifida + failure of neural tube development)
May see one of 5 telltale skin defects
- tail
- skin dimpling
- sacral pit
- hair tuft
- lipoma
Myelodysplasia: Any developmental defect of the spinal cord
2. Spina Bifida Cystica
Vertebral laminae absent with prolapse of neural elements
A. Myeloschisis / Myelocoele
- neural plate material spread out over the surface (most severe form)
B. Myelomeningocoele
- prolapse of cord & dura in defect (commonest)
C. Meningocele
- prolapse of dura only
- usually no neurological deficit
3. Spina Bifida Occulta
Congenital spinal disorder where the two halves of posterior arches fail to fuse leading to bony abnormality
- defect is hidden
- may have diastematomyelia
- seen in 5-10% of radiographs in normal population
- not really related to spina bifida cystica and probably not prevented by folate
Epidemiology
1 / 1000 live births
- varies with geographic location
- Ireland, England, Wales - 5/1000
- Australia & USA 1/1000
1:20 with one affected sibling
1:10 with second affected sibling
Girls > boys
Aetiology
Multifactorial nature
- polygenic inheritance with teratogenic enviromental factors
Decreased RBC folate associated with increased risk
- avoid folate antagonists
- folate taken prior to conception reduces rate of spina bifida by 70%
- need to take before first month of pregnancy
- 0.4 mg per day normally
- 4mg per day if have a previous child with SBC
Pathogenesis
Early problem 26th gestational day (24-28)
Two theories
A. Failure of neural tube to close
B. Initially closed tube which reopens due increased intraluminal pressure
The latter theory is favoured & explains other defects such as diastematomyelia etc
Prenatal Screening
Should be able to detect 90% fetus with an exposed neural defect
- small skin covered defects may be missed
Maternal alphafetoprotein increased
- test at 16-20 weeks
- detects 90% of spina bifida
- will justify other investigations
- amniocentesis (spontaneous abortion risk 1:200)
Ultrasound
- vaginal at 10-12 weeks will identify anencephaly & some spina bifida
- standard 16-18 weeks identify anencephaly & 80% spina bifida
Management of early detection
- deliver by C section to avoid contamination by vaginal flora
- secondary infection which then can lead to loss of level
NHx
Survival
- without repair nearly 100% will die
- especially in pre-antibiotic day
- increase survival to 50% at 25 years
- antibiotics / selective closure / shunting
Neurology
- not static & there is often a decline during childhood especially first 4 years
- 60% have neurological deficiency in upper limb
- this is due to syrinx / Arnold Chiari / hydrocephalus
Function
- only 30% are functionally independent as adults
- only 30% will have full or part-time jobs
- 65% will have normal intelligence
Wheelchair
- 100% if L1 or L2 or higher
- 80% if L3, L4, L5
Modified Asher & Olson Classification
Lowest level at which Grade 3 power is available i.e. antigravity power
Thoracic: no grade 3 strength in lower leg muscles
L2: hip flexion
L3: knee extension
L4: knee flexion
L5: ankle dorsiflexion
Sacral: ankle plantarflexion
i.e. L4 and below are most likely to walk
Clinical Features
1. Hydrocephalus
Incidence 90%
- of these 80% will require shunt
- inserted at time of the defect closure
IQ normal if no hydrocephalus
Must constantly be on lookout for blocked shunt
- deteriorating neurological function
- bulging fontanelle
- poor muscle function
2. Hydromyelia / Syringomelia / Syrinx
Incidence 50%
- related to hydrocephalus
- fourth ventricle communicates with the central canal of cord
- increased hydrocephalus pushes fluid into cord
Leads to
- increased lower limb paralysis & back pain
- progressive scoliosis
- weak upper extremities with increased tone
Usually settles with V-P shunt
May need drainage prior to spinal procedure
3. Arnold - Chiari Malformation: (Type II in 90%)
Displacement of medulla into cervical canal
- cerebellar tonsils herniated below foramen magnum on MRI
Symptoms
- periodic apnea
- stridor
- weak / absent cry
- nystagmus
- upper extremity spasm & weakness
May resolve with shunt / if not then surgically decompress
4. Tethered Cord
Attachment of cord to meningocoele sac
- prevents normal upward migration of the cord during growth
- almost universal to some degree
Only small number have symptoms
- buttock & posterior thigh pain
- increased spasticity & weakness in lower extremities
- progressive scoliosis the classic presentation is progressive
- cavus foot deformity in young child
- rapid deterioration in quadriceps power in teenager
Surgical release will halt progression but not restore function
5. Urinary Complications
One of major causes of morbidity & mortality in childhood from renal failure
Causes
- incontinence
- hydronephrosis
- recurrent UTI
Management
- intermittent catheterisation
- bladder augmentation
6. Skin anaesthesia
Pressure sores major problem with casts
- hip spicas should always include feet
7. Latex Allergy
IgE mediated
Should always provide latex free operating environment
- assume allergy and prevent development
Can screen with RAST (radioallergosorbent test) / skin test / IgE assay
- IgE assay most sensitive & specific
8. Fractures
Classic exam scenario / clinical photo
- supracondylar femoral fracture is commonest
Often present late
- picture of infection (redness, swelling, warmth)
Treat with removable splints for short time as get very stiff
9. Upper Extremity Function
60% have abnormality of UL function
- usually weakness with increased tone
Risk factors
- high level
- multiple shunt revisions (ie cerebral damage from hydrocephalus)
- syrinx etc
10. Orthopaedic Deformity
Causes
- muscle imbalance 2° to UMN or LMN lesion
- intrauterine posture
- habitual posture after birth
- congenital malformation (eg club foot)
- arthrogryposis
Problems
- scoliosis
- hip FFD / Dislocation
- Knee hyperextension / flexion contracture / valgus
- teratological CTEV
- cavus foot
- charcot foot
- ulceration
Orthopaedic
Goals
1. Ambulation
- level dependent
2. Hips
- reduce hips if unilateral / low level / walk
- different to CP as not painful
3. Foot
- keep shoeable & plantigrade
- even if in wheelchair
- avoids ulcers and amputation
4. Spine
- 80% develop scoliosis
5. Prevent pressure areas
Always manage in spina bifida clinic
Muscle charting
- should start 24 hours after birth
1/3 Complete LMN & loss of sensation & bowel control below affected level
1/3 Complete lesion at some level but distal segment of cord preserved
- mixed picture of intact DTR & spasticity
1/3 Incomplete & some movement & sensation preserved
Levels
L1 Level
Muscles
- iliopsoas grade 2 or better / some weak hip flexion
Position
- Hip flexed, abducted & ER
Ambulation
- HKAFO - hip knee ankle foot orthosis
- RGO - reciprocating gait orthosis, when one hip flexes the other extends
- adults usually wheelchair bound
L2 Level
Muscles
- iliopsoas, sartorius & adductors grade 3 or better
- hip flexion & some adduction
Position
- hip flexed and adduction
- FFD of hip may develop
Ambulation
- most ambulate as children in HKAFO
- FFD may need to be corrected first
- adults usually choose wheelchair
L3 Level
Muscles
- quadriceps grade 3
Position
- hip flexed & adducted
- knee extended
- Hip subluxation & dislocation common due to unopposed hip adduction & flexion
Ambulation
- usually household ambulators
- grade 4 quadriceps - 80% community ambulators / 98% household ambulators
- grade 3 quadriceps - need KAFO to walk & 88% in wheelchair
- patients with quads & good abductors can ambulate without aids
L4 Level
Muscles
- medial hamstring grade 3
- Tibialis anterior 3 or better
- quadriceps grade 5
Position
- hip flexed & adducted
- knee extended
- ankle in varus due to T anterior
Ambulation
- walk in AFO
Surgery often required to maintain hip & knee extension / foot plantigrade
L5 Level
Muscles
- lateral hamstrings >=3
- G medius >=2
- T posterior >=3
Position
- calcaneovalgus or calcaneus foot
- need T anterior to T Achilles transfer age 3 to prevents foot drop gait
Ambulation
- 95% community ambulators throughout life
Sacral Level
Muscles
- Gastroc/Soleus >/=2
- G medius >/=3
- G maximus >/=3
Position
- clawing of toes & cavus foot from intrinsic minus
Ambulation
- usually brace free but may need special shoes
- ie arch supports
At high risk of heel ulcers due to foot imbalance / calcaneus / nil S1 protective sensation