What are the pre‑anesthetic, intra‑operative, and postoperative considerations for a neonate with Arnold‑Chiari (Chiari II) malformation and myelomeningocele undergoing corrective myelomeningocele surgery under general anesthesia?

Anesthetic Management for Neonatal Myelomeningocele Repair with Arnold-Chiari II Malformation

Perform myelomeningocele repair within 48 hours of birth under general anesthesia with meticulous attention to airway management and positioning, as these neonates have profound brain stem compression that can cause life-threatening respiratory complications both intraoperatively and postoperatively. 1, 2

Pre-Anesthetic Assessment and Preparation

Critical Airway and Neurological Evaluation

• Assess for signs of severe brain stem dysfunction before induction, specifically evaluating for bilateral vocal cord paralysis, stridor, apneic episodes, and swallowing difficulties, as these indicate profound compression and predict poor surgical outcomes and anesthetic complications 3, 4
• Bilateral vocal cord paralysis is the most ominous sign—if present preoperatively, expect difficult airway management and poor neurological recovery even after decompression 4
• Evaluate for opisthotonos, arm weakness, and cranial nerve deficits, as 31% of symptomatic neonates deteriorate dramatically within 2 weeks of initial presentation 3

Hydrocephalus Status

• Verify that hydrocephalus is absent or adequately controlled before proceeding with myelomeningocele repair, as uncontrolled hydrocephalus is often the primary driver of brain stem symptoms and must be addressed first 5, 6
• Approximately 40% of postnatal repair patients will develop shunt-dependent hydrocephalus requiring constant neurosurgical surveillance 2
• If the neonate has symptomatic Chiari II with hydrocephalus, external ventricular drainage may resolve symptoms in 40% of cases, potentially avoiding the need for immediate myelomeningocele repair under compromised conditions 5

Infection Risk

• Initiate prophylactic antibiotics immediately if surgery cannot be performed within 48 hours to prevent meningitis and ventriculitis, as infection is a major contributor to the 10% mortality rate in these neonates 1

Intra-Operative Considerations

Positioning and Exposure

• Position the neonate prone for myelomeningocele repair, protecting the exposed neural placode from trauma and avoiding pressure on the abdomen that could increase intracranial pressure 2
• The defect typically requires careful dissection and closure in layers, with the anatomic level determining long-term ambulatory prognosis 1

Airway Management During General Anesthesia

• Anticipate difficult airway management and potential laryngospasm in neonates with stridor or vocal cord dysfunction from brain stem compression 3
• Have equipment immediately available for emergency airway management, including fiberoptic bronchoscopy and surgical airway capability
• Avoid neuromuscular blockade reversal agents that could precipitate laryngospasm in patients with pre-existing vocal cord dysfunction

Hemodynamic and Respiratory Monitoring

• Monitor for sudden respiratory depression or apnea, as brain stem compression at C-1 to C-4 level (present in the majority of cases) causes unpredictable respiratory control 3
• A transverse dural band constricting the dural sac at C-1 occurs in 41% of patients, and arachnoidal adhesions in 23%, both contributing to acute brain stem dysfunction 3
• Maintain normocapnia and avoid hyperventilation, as changes in cerebral blood flow could worsen brain stem ischemia

Anesthetic Agent Selection

• Use anesthetic agents that preserve brain stem perfusion and avoid those that depress respiratory drive excessively
• Consider total intravenous anesthesia to allow rapid emergence and immediate neurological assessment
• Minimize opioid use intraoperatively given the high risk of postoperative respiratory depression from baseline brain stem dysfunction

Post-Operative Management

Intensive Respiratory Monitoring

• Monitor with transthoracic impedance apnea monitors, continuous electrocardiogram, and pulse oximetry for at least 36 hours postoperatively, with particular vigilance in the first 8 hours when respiratory events are most common 2
• The majority of deaths in these patients are attributed to respiratory failure, making aggressive respiratory monitoring non-negotiable 3, 4

Neurological Assessment

• Assess vocal cord function, swallowing ability, and cranial nerve function immediately upon emergence to establish a postoperative baseline 3, 4
• Patients with bilateral vocal cord paralysis preoperatively have the worst prognosis—only 1 in 6 will improve even after surgery 4
• Early recognition of deterioration and prompt intervention are essential, as 31% of neonates experience irreversible neurological deficits if treatment is delayed 3

Pain Management

• Use multimodal analgesia with minimal opioids given the profound risk of respiratory depression from brain stem dysfunction
• Regional techniques (caudal or local infiltration) should be considered to minimize systemic opioid requirements

Ongoing Neurosurgical Surveillance

• Maintain close communication with neurosurgery regarding development of hydrocephalus, as approximately 70-80% of myelomeningocele patients develop this complication 1
• Monitor for signs of shunt-dependent hydrocephalus, which develops in 40% of postnatal repair patients 2
• Watch for tethered cord syndrome, which causes deterioration in ambulatory function in both prenatal and postnatal repair patients 1, 7

Critical Pitfalls to Avoid

• Do not delay surgery beyond 48 hours without antibiotic coverage, as infection risk increases dramatically and contributes to the 10% neonatal mortality 1
• Do not assume that myelomeningocele repair alone will resolve brain stem symptoms—if hydrocephalus is present, ventricular drainage must be addressed first or simultaneously 5, 6
• Do not extubate a neonate with bilateral vocal cord paralysis without a clear airway management plan, including potential tracheostomy, as these patients have the highest risk of postoperative respiratory failure 4
• Do not underestimate the rapidity of deterioration—neonates can progress from initial symptoms to profound brain stem dysfunction within days, making urgent surgical intervention critical 3