Physiology of Meningomyelocele and administration of Anesthesia

1. MENINGOMYELOCELE
Speaker: Dr Bhagirath.S.N
Moderator: Dr Sarika

2. Meningomyelocele
• Incidence: 1 in 1000 live births
• Most common congenital primary neural defect
Meningo: involving the meninges
Dura
Arachnoid
Myelocele: involving the neural components
Neural placode
Nerve tissue
roots
CSF
Components of a
meningomyelocele

3. Embryology
Neural tube development-failure of closure of neural tube causes a
meningomyelocele

4. Embryology…….(contd)
It presents most commonly over the lumbar, sacral vertebra as a cystic mass

5. Meningomyelocele
•Coexistent morbidities:
 Orthopedic problems in the child
 Urologic complications
• Antenatal diagnosis
 Ultrasonography
 biochemical tests:
α fetoprotein levels in
the maternal serum and
amniotic fluid

6. Associated Conditions-Arnold Chiari Malformation
•Brain stem anomaly
•Caudal displacement of
 Cerebellar vermis
 Medulla oblongata
 Cervical spine
 Kinking of the medulla
 Obliteration of cisternamagna
• Clinical presentation
 Stridor, Apnea, bradycardia
 aspiration pneumonia
 sleep disordered breathing pattern
 vocal cord paralysis
Lack of co-ordination & spasticity

7. Associated Conditions-Arnold Chiari Malformation….(contd)
• small sized skull housing a normal sized posterior fossa
Approach to a meningomyelocele patient….
• To operate within 24 hours-reduces the neurological deficits
• Close the defect and place a shunt
• or delay placing a shunt and instead operate once hydrocephalus sets in
• Intra uterine procedure is less favoured
• Posterior fossa decompression should always be a last resort

8. Meningomyelocele-preoperative care
•An exposed neural placode risks
 Trauma
 Continous CSF leakage-countered by full strength balanced salt solution
 place a soaked gauze to prevent desiccation
 Maintain extracellular fluid
 Avoid hypothermia

9. Meningomyelocele-Peri operative care
Anesthetic technique
1. Positioning:
Supine: the defect ought to rest in a “doughnut” to minimise trauma.
Lateral: leads to difficult intubation
Prone: Care is taken to avoid pressure on epidural venous plexus to
maintain bleeding and allow adequate ventilation.
2. The child usually has an IV cannula in place with maintenance fluids.
3. Premedication—atropine 20 mcg/kg IV prior to induction if desired.
4. Induction is IV or inhalational as preferred. The child may need to be
supported on a cushion or jelly ring to avoid pressure on the lesion or placed in
the lateral or semi-lateral position depending on the exact anatomy.

10. Meningomyelocele-Peri operative care
Anesthetic technique
5. Endotracheal intubation with an armoured ETT and IPPV are required.
6. Maintenance is with volatile agents in oxygen and air or nitrous oxide.
7. Consider arterial and central line depending on the size of the lesion.
8. The patient is positioned prone for surgery. Rolls of soft material or jelly
bolsters are placed under the shoulders and pelvis to allow free abdominal
movement during ventilation.
9. The extremities are padded.
10.The surgeon may wish to stimulate nerves during the procedure. Discuss this
before giving a long acting neuromuscular blocker.
11.Blood loss is not usually a problem but some large lesions require extensive
undermining of skin to fashion a flap or flaps when bleeding does become an
issue.

11. Meningomyelocele-Peri operative care
Anesthetic technique
12.The surgical site is usually infiltrated with LA and adrenaline to ensure
haemostasis. Additional opioid analgesia (morphine sulphate 25-50 mcg/kg or
fentanyl citrate 1-2 mcg/kg) can be given if this is inadequate. The sensory
level is usually unclear at this point so analgesic requirements are variable.
13.IV antibiotics are given according to surgical request or local protocol.
14.If stable, extubate at the end of procedure.

12. Meningomyelocele-Post-operative care
Watch out for
• Stridor
• Apnea
• Bradycardia
• Cyanosis
• Respiratory arrest
Secondary to brain stem herniation
If shunting is not done, then watch out for
symptoms associated with hydrocephalus
•Lethargy
•Vomiting
•Seizures
•Apnea
•Bradycardia
•Cardiovascular instability.
If symptoms worsen, proceed with shunting