أسئلة التاسعة جراحة رابعة دمياط (نيورو)

Neural Tube Defects

• Neural tube defects relate to neurosurgery
• They occur because of complications during neurulation
• They are listed as costing 5 LE

Normal Development of CNS

• There are three germ layers
• Ectoderm germ layer
• Mesoderm germ layer
• Endoderm germ layer
• Stages of brain and spinal cord development & maturation:
• Primary neurulation
• Secondary neurulation
• Neuronal proliferation & histogenesis (Migration Maturation)

Neurulation

• Formation & stability of the brain and spinal cord
• Development of the CNS starts during the 3rd & 4th week of gestation
• Neurulation can be primary
• Neural fold becomes neural groove, and lastly neural tube
• Fusion of the neural tube occurs usually midline
• Any complication during neurulation results in a neural tube defect

Primary Neurulation

• It occurs during weeks 3-4
• Neural plate folds to close in the midline
• Neural fold fuses and then closes in the midline
• Neural tube formation occurs
• Cranial neuropore turns into the brain
• Caudal neuropore turns into the spinal cord

Secondary Neurulation

• It occurs during weeks 8-10
• After the cranial neuropore closes, the tube develops into 3 primary vesicles
• Forebrain = prosencephalon
• Midbrain = mesencephalon
• Hindbrain = rhombencephalon
• The primary vesicles develop into 5 secondary vesicles
• Forebrain becomes telencephalon & diencephalon
• Hindbrain becomes metencephalon & myelencephalon

Abnormalities of Primary Neurulation

• Failure of closure of cranial neuropore results in anencephaly
• Failure of closure of the caudal neuropore results in neural tube defect, or Spina Bifida
• Anencephaly results if the neural tube doesn't close at the cranial end, so the brain doesn't develop
• The condition is not compatible with life
• Results if The vertebral arch remain open and defect
• Spina bifida occulta involves closed skin over the defect, usually asymptomatic, or may be associated with other hidden types of spinal dysraphism
• Spina bifida manifesta presents with a sac over the defect filled either by CSF or spinal cord

Risk factors for neural tube defect

• Unclear causes account for over 60%
• 10% caused by Chromosomal abnormalities
• 10% caused by Environmental exposure
• General Stress and war times
• Folic acid deficiency during pregnancy
• Folic acid antagonist carbamazepine, phenytoin
• Prenatal infection or irradiation,
• Maternal factors:
• Medication use (antiepileptic drugs)
• Disease (diabetes)

Spina Bifida Classification

• Spina Bifida Occulta (Simple - Complex)
• Spina Bifida Manifesta (Meningocele - Myelomeningocele)

Spina Bifida Occulta

• Simple: Congenital absence of a spinal process with some missing lamina
• Complex:
• A defect in the spinal arch where the nerves and spinal cord are abnormal and other anomalies may be present
• A defect in the spinal arch
• Can be characterized by a small defect in the spinal arch with normal nerves and spinal cord and no other abnormalities
• No visible exposure of meninges or neural tissue
• Incidence occurs in 10-20% of cases
• Congenital absence of spinal process
• The neural tube defect is covered by skin

Spina Bifida Manifesta

• Meningocele: Congenital defect of the vertebral arch with some cystic distension of meninges.
• Myelomeningocele: Congenital defect of the vertebral arch with some cystic distension of meninges & Spinal cord
• The sac may be intact or ruptured
• Some infants may have no symptoms or only mild symptoms
• The cyst contains Meninges and CSF, but no abnormalities of the neural tissue
• Most severe & most common
• The cyst contains::
• Meninges
• CSF
• Nerves & spinal cord
• May not be covered by skin

Presentation

• Defect may be palpable
• May be overlying cutaneous manifestation:
• Dimple
• Nevus flaminous (red spot) or port wine
• Pad of subcutaneous fat
• Tuft of hair "Small hair growth"
• Often an incidental finding
• In which patient is usually intact neurologically

Risk factors

• Previous birth with MM
• Families where close relatives (siblings)
• War
• Economic disasters

Complication

• May or may not cause instability
• 1/3 have some neurologic deficit
• Structure & functional abnormality of the spinal cord or cauda equina

Spinal Dysraphism

• Associated conditions may include: Diastmatomyelia or diplomyelia., Tethered cord, Spinal lipoma, Dermoid tumors

Associated conditions

• Severe paralysis, bowel & urinary dysfunction
• Hydrocephalus with myelomeningocele is 80% of cases at the age of < 6 months
• Closure of the MM defect may convert a latent hydrocephalus to active hydrocephalus
• Chiari malformation type 2

Spinal Lipoma

• Subcutaneous lipoma passes through a midline defect in the lumbodorsal fascia vertebral arch & dura then emerges with a normally low tethered cord
• Back mass
• Presentation may consist of: Bladder problems, Foot deformities, Sensory loss, or cutaneous manifestations
• MRI lumbosacral in investigation
• A possible treatment is Release of Tethering or Reduce the buck of fatty tissue

Tethered Cord

• Abnormally low conus medullaris associated with short thickened filum terminalis
• Scoliosis (↑) or kyphosis
• Leg pain
• Increasing spasticity worsening gait
• Deterioration of urodynamic manifestations
• Cutaneous finding: tuft of hair, Subcutaneous lipoma
• Investigation: MRI lumbosacral spine low conus medullaris or with intradural lipoma
• 1. Cutting of the filum (untethering) &/or
• 2. Excision of lipoma if present

Diastmatomyelia & Diplomyelia

• Diastmatomyelia:
  • 2 hemi- cords, each with its own central canal & with a separate Dural tube &
  • Separated by rigid osseocartilaginous median septum
• Diplomyelia
  • 2 hemicords within a single dural tube
  • Separated by a non-rigid fibrous median septum

Chiari II Malformations

• A heterogeneous group of conditions with disruption of normal CSF flow through the foramen magnum
• Causally dislocated
  • cervicomedullary junction
  • pons
  • 4th ventricles & medulla
• Cerebellar tonsils located at or below the foramen magnum
• Hydrocephalus is present in most cases
• Swallowing difficulties
• Stridor
• May be progress to quadriparesis
• Arm weakness
• Apneic spell
• Weak or absent cry
• Facial weakness
• Plain x-ray
• MRI
• Laryngoscopy
• V-P shunt for hydrocephalus
• Posterior fossa decompression for
  • (Neurogenic dysphagia - stridor - Apneic spell)
• Chiari type I - Chiari III - Chiari 0 - Chiari 1.5

Evaluation & Assessment

• Lesion assessment: Measure size of defect and if the sac is ruptured or unruptured
• Neurological assessment:
  • Assessment of spinal lesion:
    1. Spontaneous movement of the lower
    2. Lowest level of neurologic function in response to painful stimulus
    3. loss of anal corrugation
  • Assessment of commonly associated Chiari malformation: 4. Measure OFC 5. Inspiratory stridor or apneic episodes
• Orthopedic assessment:
  • For sever kyphotic or scoliotic spine deformities
  • For hip & knee deformities
• Urological assessment:
  • Frequent wetted
  • Start patient on regular catheterization
• Nerve Roots:
  • T12: Complete paralysis of all muscles of lower limbs
  • L1: Inguinal region and hip flexors
  • L2: Anterior mid thigh and hip flexors
  • L3: Distal anterior thigh + Hip flexors & knee extensors
  • L4: Medial lower leg and foot + Knee extensors & ankle dorsiflexors
  • L5: Lateral leg and foot - Hallux extension & ankle plantar flexors
  • S1: Lateral side of the foot - Ankle plantar Flexors & evertors

Investigation

• CT brain: associated hydrocephalus
• MRI spine: size, tethered cord, spinal lipoma
• Orthopedic & urological investigations

Management

• Team based therapy:
  • Neurosurgery intervention: Surgical repair of the defect, Shunt surgery for hydrocephalus, Untethering of cord, Excision of the spinal lipoma, Reconstruction of the spinal canal
  • Orthopedic intervention: Surgical treatment of congenital anomalie
  • Urological intervention: Treatment of bladder complication + Catheterization for neurogenic bladder and anticholinergic drugs
  • Physiotherapy: For neurological weakness
• Pre-operative
  • If ruptured start antibiotic
  • If non ruptured Cover the lesion with soaked sterile dressing with normal saline
• Position: "Trendelenburg"

Operative

• Within 36 hours unless there is a contraindication for surgery
• Multiple layer closure is advocate
• Avoid placing tension on the neural placode
• The filum terminalis should be divided if it can be located
• The skin is mobilized and closed
• Simultaneous shunt is not usually done except if overt hydrocephalus at birth
• Other operative varieties to myelomeningocele: 1.Shunt surgery for hydrocephalus

2. Decompressive craniotomy for Chiari malformation
3. Untethering of cord
4. Excision of the spinal lipoma
5. Reconstruction of the spinal canal
6. Excision pf skin dimple

Postoperative

• Bladder catheterization regimen
• Daily OFC measurement
• Keep patient flat to reduce CSF pressure on incision
• 85% of cases occur in MM infants

Outcome with Modern Treatment

• 85% of MM infants survive
• The most common cause of early mortality is: complications from Chiari malformation respiratory arrest and aspiration
• Late mortality is usually due to shunt malfunction
• 80% will have normal IQ
• 40-85% are ambulatory with bracing
• 3-10% have normal urinary continence

Complications

• Acute complication:
  1. Hydrocephalus
  2. Neurogenic bladder
  3. Orthopedic deformity
• Long term complications:
  1. ADHD & learning disability
  2. Weight gain & Obesity
  3. Cardiovascular disease
  4. Spine deformity
  5. Fecal incontinence & constipation
  6. Sexual dysfunction
  7. Urinary tract hydroureter & hydronephrosis, UTI
  8. Lymphedema
• Intrauterine repair of myelomeningocele:
  • Can be considered but the outcome is the same as repair of the defect postnatal

Encephalocele

• Protrusion of the meninges & brain substances through a defect in the skull
• Due to failure of closure of the cranial neuropore
• Occipital is common
• Parietal
• Frontal
• Basal
• Character can be associated with hydrocephalus
• May be ruptured or intact sac
• Surgical repair or closing the encephalocele.
• Children who have developed hydrocephalus will require a CSF shunt