MENINGOMYELOCELE AND HYDROCEPHALUS

1. MENINGOMYELOCELEANDHYDROCEPHALUS Presentor : Dr. Varun Moderator : Dr. Anjali University College of Medical Sciences & GTB Hospital, Delhi email: anaesthesia.co.in@gmail.com www.anaesthesia.co.in

2. MENINGOMYELOCELE

3. Embryology • Neural tube formed by ectodermal neural crest • Occurs by 28 days of gestation • Neural crest deepens ↓ Neural groove Neurulation ↓ Neural tube

5. Myelodysplasia- Congenital failure of the neural tube to close • Anencephaly- defect in anterior closure of the neural groove with brain and skull poorly developed • Encephalocele- brain herniation through cephalad defect • Spina bifida cystica- fusion fails in the midline or caudal neural groove with Meningocele- herniation of meninges Meningomyelocele- herniation of meninges plus neural tissue

6. Etiology • Genetic • Females are more affected • More common in Caucasians and blacks • Parenteral consanguinity increases incidence • Environmental- folic acid deficiency • Teratogenic drugs- valpraote, carbamazapine • Higher prevalence in lower socio economic groups

7. Pathophysiology • Meningocele (20%) - sac containing meninges bulges through the defect. Overlying skin intact. Neurological manifestations usually absent • Meningomyelocele (80%) – contains neural elements along with meninges. Majority of defects occur in lumbosacral area. Neurological deficits distal to defect are most severe. • Spina bifida occulta – absence of bony spinous process. No clinical significance

8. Types

9. Meningomyelocele

10. Pathophysiology • Depending on severity, manifests as neurologic, motor and sensory deficits • Associated congenital anomalies may be present • Brainstem dysfunction • Hydrocephalus and ↑ICP

11. Associated anomalies • Club feet- commonest • Arnold Chiari malformation ( 80-90%) • Hydrocephalus (80%) • Neurogenic bladder(90%) • Musculo skeletal defects • Urogenital anomalies • Facial clefts • Umbilical hernia • Congenital heart diseases - rare

12. Clinical features • Fluid filled swelling at back • Paraparesis with muscle wasting • Sensory symptoms • Neurogenic bladder and bowel • Convulsions/ tonic spasms • Cranial nerve dysfunctions

13. Complications • Rupture of sac during birth process • CSF leak • Raised ICP- vomiting, convulsions, altered sensorium, irritability • Infection – fever, unconsciousness, altered sensorium (meningitis)

14. Diagnosis Prenatal • ↑ Acetyl cholinesterase and alpha fetoprotein in maternal serum and amniotic fluid ( in 2nd trimester) • Prenatal ultrasound picks up the defect in 100% of the cases

15. Management • Management of neural tube defects requires team approach with cooperation of pediatrician, neurologist, neurosurgeon and anesthesiologist • Surgery is mainstay of treatment and includes repair of the defect and a VP shunt ( if associated with hydrocephalus)

16. Management Meningomyelocele is repaired within first day or two of life. Why it is an emergency? • Rupture of sac • Spinal cord vulnerable to infection • Sepsis commonest cause of death • Surgery < 24 hours for open defects which minimizes bacterial contamination and further neurological damage • Closed lesions should be operated within 48 hours

17. Management • Many are now scheduled electively before birth for repair, because the defect is usually apparent on prenatal ultrasonography

18. Fetal surgery • Presently, open midgestationsurgery is largely reserved for closure of MMC • Defect is exposed while the rest of the fetus remains bathed in amniotic fluid in the uterus • The rationale for in utero closure of MMC appears that prolonged bathing of neurologic elements in the amniotic fluid worsens the neurologic outcome

19. Fetal surgery • Advantages – decreases need for post natal ventriculoperitoneal shunting and incidence of Chiari malformation. Also improves motor function • Currently restricted to patients enrolled in the NIH-sponsored Management of Myelomeningocele Study (MOMS trial)

20. A fetus with myelomeningocele (MMC) exposed for in utero midgestation repair. The fetus is turned so that the MMC defect is exposed. Special uterine staples can be seen framing the hysterotomy. The red rubber catheter coming from the left side of the image is used to instill warmed crystalloid to maintain amniotic fluid volume. (From Myers LB, Cohen D, Galinkin J, et al: Anaesthesia for fetal surgery, Paediatr Anaesth 12:569, 2002, with permission from Wiley-Blackwell.)

21. Anesthetic Management for Surgical Repair of Meningomyelocele

22. Anesthetic concerns

23. Pre Anesthetic Evaluation • Neurological impairment including • cranial nerve function and ability to protect airway • Neurological deficits • signs of ↑ICP • Volume status and IV access • Any drug therapy • Steroids • Mannitol, diuretics • Anti - convulsants

24. Pre Anaesthetic Evaluation • Investigations • Hb, Blood Grouping and Cross Matching • X Ray chest ( if required) • Pre op preparation • Pre op advice • Explain NPO to parents • Adequate hydration to be maintained • Usually no pre medication is required

25. Monitoring • Heart rate • SpO2 • Capnography • Precordial stethoscope • Urine output • NIBP • ECG • Temperature • Blood loss • Clinical

27. Induction of anaesthesia • Intubation is a challenge • In most cases, Supine position- with sac resting in a donut shaped cushioned ring and weight of child supported on pelvis and portions of spine not involved with the defect • For large defects, Lateral position- with head held in midline by an assistant • Assistant must be available to ensure that no physical trauma to neuroplaque occurs • Difficult airway – awake intubation with atropine premedication (20mcg/kg, minimum 0.1 mg) and preoxygenation

28. Induction of anaesthesia • Induction may proceed by mask inhalation or by intravenous administration of thiopental, glycopyrrolate, and a muscle relaxant. • Either a NDMR or succinylcholine can be used safely • Intubation with reinforced tracheal tube is recommended

30. Maintenance of anesthesia • Patient positioning - prone position • Abdomen should be free - rolls under chest and pelvis • Excessive rotation/flexion of the neck avoided  brainstem compression, rise in ICP • Extremities relaxed and padded • Eyes protected with ointment and thick pads

32. Maintenance of anesthesia • Anesthetic agents • 60% N2O in O2 with Isoflurane/Sevoflurane • Analgesia maintained with IV Fentanyl. Avoid high dose opioids- risk of post operative apnea • Muscle relaxants • NDMR (Atracurium, Vecuronium) • Used with caution when nerve stimulation is used to identify neural structures

33. Maintenance of anesthesia • Ventilation • Maintain normocapnia • Prevent barotrauma • Avoid prolonged exposure of high FiO2 • Fluid management • IV fluids – RL is used, IV dextrose solution5% if patient is hypoglycemic • High third space losses • Blood loss is not excessive ( about 30 ml, or 10% of blood volume). However if lesion is extensive, blood loss increases significantly

34. Maintenance of anesthesia • Body temperature • Conservation of body heat is important • Prone to hypothermia because of large area of exposed tissue • Autonomic control below the level of defect is abnormal • Operating room should be warmed to 27°C before surgery and until infant is draped • During surgery, forced hot air warmer is used • Humidification of inspired gases prevents heat loss

35. Latex allergy • Myelodysplasia patients are at high risk of developing allergic reactions to latex. • Due to repeated exposure to latex products during surgery, or repeated bladder catherizations. • To prevent early sensitization, myelomeningocele patients should be treated as if they are latex allergic

36. Latex allergy • Manifests as hypotension and wheezing with or without rash • Anaphylaxis should always be anticipated • Treatment – removal of source of latex and administration of IV fluids and vasopressors • Post operatively, respiratory status should be carefully assessed. • Prone to develop allergic reactions to other substances later in life

38. Emergence • Elimination of anesthetic agents • Reversal of neuromuscular blockade • Assessment of airway patency • Neonates at risk for apnea and those with severe neurologic deficits should be extubated fully awake

39. Post operative care • Oxygen therapy • Nursing in prone/ lateral position • Pain relief by IV fentanyl, paracetamol suppositories • Insertion of an epidural catheter by the surgeon under direct vision can provide a conduit for the administration of local anesthetics and opioids for the management of postoperative pain

40. Post operative care • Watch for signs of brain stem dysfunction • Watch for signs of raised ICP

41. Points to remember • Spinal dysraphism is the primary indication for laminectomies in pediatric patients • Patients have multisystem diseases that result from a severe injury to the developing CNS early in gestation • At high risk for developing a hypersensitivity to latex

42. Points to remember • Meningomyelocele should be repaired as soon as possible to prevent complications • Intubation may be difficult in these cases • Prone position has its own hazards and precautions to be taken • Body temperature to be maintained • Post op oxygen and pain relief to be given in all cases

43. Hydrocephalus

44. Physiology of CSF andPathophysiology of Hydrocephalus

45. FUNCTIONS OF CSF Mechanical cushion to brain Source of nutrition to brain Excretion of metabolic waste products Intracerebral transport medium Control of chemical environment Autoregulation of intracranial pressure

46. Production of CSF • Choroidal – choroid plexus of the venticles • Extrachoroidal • Ependyma • Neighbouring brain substance

47. Ventricular system • Lateral ventricles > foramen of Monro to the midline third ventricle • Third ventricle to fourth ventricle via aqueduct of Sylvius • 3 exits from the 4th ventricle to cisterns • midline foramen of Magendie • paired lateral foramina of Luschka • Cisterns connect to the subarachnoid spaces • Absorbed at the arachnoid villi

48. CSF pathways

49. Hydrocephalus Definition: • It is the condition of excess cerebrospinal fluid accumulation in the head as a result of disturbance of formation, flow or absorption • Term arises from greek, hydro ( water) and cephalus (head) Epidemiology: • Infantile HCP: 3-4 per 1000 live births • As a single congenital disorder: 0.9-1.5 per 1000 live births

50. TYPES OF HYDROCEPHALUS • OBSTRUCTIVE OR NON-COMMUNICATING (obstruction within the ventricular system) • NON OBSTRUCTIVE OR COMMUNICATING (malfunction of arachnoid villi)