Awake Craniotomy in Children

Introduction

• AC is a brain surgery procedure performed while the patient remains conscious and communicative, which allows a wider extent of tumor removal, reduces postoperative neurologic deficits, and improves survival rates.^1,2
• Compared to standard craniotomy, AC is associated with:^2,3
• Lower requirement for high dependency care
• Shorter hospital stays
• Reduced costs
• Fewer neurological deficits
• Decreased postoperative pain
• Decreased nausea and vomiting

Patient Selection

Indications

• Table 1 lists indications for an AC.
• Well-motivated and mature patients who can tolerate lying still for several hours and cooperate during testing are the best candidates for AC.^1,4
• An extensive preoperative evaluation on a separate day should be performed to clarify operative-day expectations and to identify any concerns or contraindications to AC. Patient refusal and inability to cooperate and obey commands are absolute contraindications for AC. Contraindications are listed in Table 2.¹

Preoperative Preparation

• A multidisciplinary team (neuroanesthesiology, neurosurgery, neuropsychology, and neurology) should evaluate patient suitability and coordinate perioperative planning, including positioning, airway management, anesthetic technique, monitoring, and anticipated complications.⁵
• Early preoperative assessment and counseling are essential to minimize anxiety and ensure cooperation. Patients should receive a clear explanation of the rationale for AC, procedural steps, expected discomfort, intraoperative testing requirements, and potential adverse events, and must demonstrate the ability to remain still.^1,2 The ability to stay still for a preoperative planning MRI is one such example.
• Preoperative medical recommendations include maintaining routine medications and optimizing comorbid conditions.^2,5
• Care should be taken to not give medications that may interfere with appropriate intraoperative participation, including preoperative benzodiazepines. Continuation of antiepileptic drugs through the morning of surgery should be at the discretion of the neurology team if electrocorticography (ECOG) is planned.

Intraoperative Management

• Monitoring: Standard American Society of Anesthesiologists monitors should be used in all cases, and the placement of an arterial line should be considered. A processed electroencephalography monitor (bispectral index) may be used to guide anesthetic dose, although technical issues related to placement with respect to prepping/draping of the craniotomy site must be considered. Precordial Doppler can be considered to detect venous air embolism in sitting positions.¹
• Patient comfort is of utmost importance. Room temperature adjustment and warming blankets should be used to prevent hypothermia and shivering.5 Hyperthermia should also be avoided as patients are usually fully draped and secured and excessive heat can be uncomfortable.

Patient Positioning

• The lesion location determines the patient’s position. Due to the location of the eloquent cortex and right-hand dominance of the general population, most lesions for AC are left-sided, temporal or parietal, and can be accessed in supine or lateral positions. The semi-sitting position is commonly used in deep brain stimulation (DBS) because it optimizes venous drainage, reduces surgical field bleeding, and enhances patient comfort during prolonged stereotactic procedures.
• A horseshoe headrest or Mayfield pins can be utilized as per the surgeon’s preference.
• Patient positioning and draping must allow direct patient interaction and free access to the airway.³

Scalp Block

• A scalp block, frequently bilateral, is essential for effective analgesia during AC. It provides hemodynamic stability, decreases the stress response to painful stimuli, and makes the procedure tolerable with less narcotic administration.^1,3
• Seven nerves on either side of the scalp (Figure 1) are blocked. Ropivacaine with epinephrine 1:200,000 is commonly used as it provides both a rapid onset and a long duration of action.
• Further supplemental local can be administered by the surgeon to incision and dura as needed.^4,5

Anesthetic Techniques

• Anesthetic goals include adequate analgesia and sedation with a safe airway, hemodynamic stability, optimal operating conditions, and an alert, cooperative patient for intraoperative neurological assessment. Techniques vary by surgeon, pathology, and patient factors. Various techniques have been described which fall into three main categories: MAC technique, AAA technique with or without airway instrumentation, and local anesthesia alone.³

MAC Technique

• MAC is administered during the initial stimulating portions of the procedure, including scalp block, application of the Mayfield pins if used, skin incision, dura incision, and removal of the bone flap. Sedation is stopped or decreased during cortical mapping/awake testing and restarted during closure.
• A smooth transition to the awake phase is the primary benefit of the MAC technique . The MAC technique also has shorter intraoperative times compared to AAA.⁶
• Challenges include titration of medications for each stage of the procedure and airway compromise.⁴

Choices of Sedative Medications

• A frequently used sedative regimen includes low-dose propofol and remifentanil infusions titrated to spontaneous respirations without any airway obstruction.
• Dexmedetomidine is a highly selective α-2 adrenergic receptor agonist and has emerged as a suitable sedative agent for AC. It provides sedation, analgesia, and anxiolysis without any significant respiratory depression and without interfering with ECOG. It can be used as a solo agent or a rescue agent, but is commonly utilized as an infusion adjunct.^3,5
• Remimazolam, an ultra-short-acting benzodiazepine, is a newer agent that can be utilized for AC as an adjunct with other infusions.⁷

AAA Technique

• General anesthesia (GA) is induced at the start, and the airway is secured with an endotracheal tube (ETT) or supraglottic airway (SGA). The patient is kept under GA during the stimulating part of the surgery. Once the dura is open, the patient is awakened for testing. To minimize discomfort, the patient is re-anesthetized following tissue resection for wound closure.⁵
• This technique has the advantages of a secured airway during the first stage, allowing for hyperventilation and limiting patient movement.^2,3
• The main disadvantage of the AAA approach is the potential risk of emergence of delirium before intraoperative neurophysiologic testing and brain mapping or movement/coughing during removal of the airway. Medications should be immediately available to rapidly return to GA if needed.³

Choices of Anesthetic Agents

• Total intravenous anesthesia (TIVA) using propofol and remifentanil infusion is commonly used. For awake testing, TIVA is reduced or stopped.
• Alternatively, rapid-acting inhalation agents, such as sevoflurane, can be used. However, inhalational anesthetics have the potential to increase intracranial pressure and induce nausea and vomiting during the awake stage.^2,5

Local Alone Technique

• This technique is performed using only a scalp block without sedation; good patient education and cooperation are essential.
• Local anesthesia alone removes the risk of excessive sedation or airway compromise.
• This technique is rarely used because patients benefit from some degree of sedation. However, it can still be considered in patients who may not tolerate sedation, in patients at high risk of airway compromise, or in patients undergoing DBS.³

Intraoperative Complications

• Overall, AC is safe and well-tolerated, but many complications have been described. Several studies have examined complication rates; however, due to differing case mixes and the variety of anesthetic techniques used, incidence rates vary widely. However, catastrophic complications are very rare.³

Failure of AC

• Failure occurs in less than 2% of the patients. Conversion to GA before completion of mapping occurs in ~2% of adult and ~4% of pediatric cases.^2,4
• Reasons for failure include inability to have the patient complete intraoperative testing, uncontrolled intraoperative seizures, airway events, or brain swelling.

Seizures

• Incidence ranges from 2-20%, occurring most commonly during brain mapping/direct stimulation. Most seizures are focal and brief and resolve spontaneously, though generalized seizures can occur. However, they are associated with a higher incidence of transient motor deterioration and longer hospital stays.¹
• Seizure presentation may include sudden loss of consciousness, localized or generalized tonic-clonic activity, or the development of a new neurological deficit. If the patient is anesthetized, they may have unexplained tachycardia, hypertension, or a sudden rise in end-tidal CO₂.³
• Management should begin by discontinuing cortical stimulation. Irrigating the brain with sterile iced saline (3-4°C) is very effective at aborting seizures. If this is ineffective, propofol may be considered. For repeated or prolonged seizures, antiepileptics (e.g., midazolam, phenytoin, levetiracetam) can be administered. However, these agents may interfere with intraoperative neuromonitoring and should be used judiciously.^1,5

Hemodynamic Instability

• Hypertension is commonly secondary to pain, inadequate sedation, agitation, and anxiety, but may also result from hypoxia, hypercapnia, raised intracranial pressure, pre-existing hypertension, or urinary retention. Management includes treating the underlying cause, providing analgesia, augmenting the scalp block, increasing sedation, optimizing ventilation, and using antihypertensives such as labetalol or esmolol as a temporizing measure.^3,4
• Hypotension may occur from sedation, anesthetic agents, or surgical manipulation. It should be managed by addressing the underlying cause and administering intravenous fluids and/or vasopressors.³

Brain Swelling/Cerebral Edema

• Bulging dura mater during lifting of the craniotomy flap is often due to peritumoral edema. Contributing factors include inadequate corticosteroids, airway obstruction, hypercapnia, hypoxia, hypertension, raised venous pressure, and venous outflow obstruction.
• Management should include checking the airway, SpO₂, EtCO₂, and vital signs, as well as assessing the level of sedation, and checking if the patient is coughing or straining.

Respiratory Depression/Airway Obstruction

• This presents with cyanosis or decreased oxygen saturation and may cause bradycardia, hypertension, or drowsiness.
• Management includes giving 100% oxygen and relieving airway obstruction with airway adjuncts, SGA, or ETT as appropriate. If respiratory depression occurs, sedation or opioids should be reduced or stopped. Oral or nasopharyngeal airways may relieve airway obstruction, but assisted ventilation and a supraglottic device may be needed.^1,3

Nausea and Vomiting

• Nausea and vomiting are relatively common but usually preventable. Pre-emptive antiemetics and dexamethasone should be given at the start of surgery.⁵
• Risk factors include a history of nausea, surgical manipulation, pain, hypotension, anesthetic technique, and raised intracranial pressure.
• Assessment should include evaluating for a surgical cause, such as dural traction, and assessing for signs of increased intracranial pressure.
• The patient should be reassured, and the causes should be addressed. Consider administering a combination of antiemetics from different classes, along with a fluid bolus. Dehydration exacerbates nausea, so the mannitol dose should be kept at or below 0.5 g/kg.^3,4

Agitation and Restlessness

• Agitation is among the most common complications of AC, particularly in younger patients. It is usually caused by anxiety, pain, or discomfort from positioning, urinary catheter discomfort or urinary retention, hypoxia or hypercapnia, post-ictal state, and neurological deterioration.
• Reassure the patient that they are safe. Also check the airway, exclude hypoxia or hypercapnia, check heart rate and blood pressure, and assess for seizure activity or new neurological deficit.³

Pain

• Even with successful regional blocks, patients can experience pain during surgery, typically associated with manipulation of skull-base structures or traction on pain-sensitive intracranial structures.²
• Additional management options include skin infiltration at pin sites, placing pledgets soaked with local anesthetic on the dura, administering boluses of short-acting opioids, and giving intravenous acetaminophen.⁵
• Positioning pain is also possible and should be addressed.

Venous Air Embolism

• Venous air embolism is a rare but catastrophic complication, and sitting AC further increases the risk. The incidence is 20-40% in the sitting position.¹
• In an awake patient, continuous coughing with a fall in oxygen saturation and tachypnea should raise suspicion of venous air embolism. In the anesthetized patient, signs include sudden end-tidal CO₂ reduction, tachypnea, refractory coughing, and chest pain.³
• Assessment requires a high index of suspicion and monitoring for end-tidal CO₂ decrease, hypoxia, hypotension, and arrhythmias; precordial Doppler is the most commonly used detection device, while transesophageal echocardiography is the most sensitive (detecting as little as 0.02 mL/kg of air) but is invasive.¹
• Management includes informing the surgeon, flooding the operative field, lowering the operative site below the level of the heart, protecting the airway and increasing inspired oxygen fraction, maintaining blood pressure with fluids or vasopressors, and providing other supportive treatment as needed.³

Postoperative Care

• Continued assessment for new-onset neurological deficits and seizures should be performed. The patient should be kept in a head-up position.⁵ Neurologic deficits may fluctuate due to postoperative swelling. Patients commonly have postoperative imaging after resection.
• Multi-modal analgesia should be provided. Postoperative analgesic requirement and the incidence of nausea and vomiting are lower in AC than in craniotomy under GA.¹
• The patient is usually transferred to the intensive care unit after surgery.¹
• AC reduces the number of days in the intensive care unit and overall hospital stays, and reduces neurological deficits.¹

Considerations in Pediatric Patients

• The younger the child, the more difficult it is to cooperate and cope with AC. The minimum age for awake neurosurgery has not been well established; the youngest reported case is 7 years. There is no defined role for AC in children <10 years due to non-cooperation and poor brain mapping sensitivity.⁵
• Developmental and psychological maturity should be prioritized over chronological age. Poor communication impairs intraoperative cooperation, which is the most common cause of failure in children. The awake phase is terminated prematurely in 4% of pediatric cases due to excessive pain or fear, compared with only 2% in adults.^4,5
• Incidence of most intraoperative complications is comparable to that in adults, including seizures, intraoperative motor and language deficits, bradycardia, and apnea.⁸
• Clinicians should explain the rationale and value of the patient’s participation and describe the procedure progression in a developmentally appropriate manner, including a realistic depiction of the operating room, expected discomforts, sounds, and faces the patient will see. Some clinicians arrange simulated theater experiences that closely replicate operating room attire, lighting, monitors, and positioning to assess the child’s coping skills.⁵
• The most reported anesthetic techniques in children were AAA protocols using propofol and remifentanil or fentanyl, with or without dexmedetomidine, and scalp block, although MAC technique has also been described.^7,8