Awake Craniotomy

Question 1

A 25 year-old male patient is listed for an awake craniotomy for excision of
a brain tumour. He has no other medical comorbidities. What are the indications for an awake craniotomy?

Answer 1

• Excision of tumours or AV malformations from specific areas of the brain e.g. close to eloquent speech sensory and motor areas. Awake surgery allows for continuous monitoring of function to minimise postoperative neurological impairment.
• Functional neurosurgery including some surgery for epilepsy.
• Insertion of deep brain stimulators.

Question 2

What added information would you like prior to proceeding with this case?

Patient factors?

Answer 2

• Take an anaesthetic history focusing on any medical conditions, previous anaesthetics and the airway.

The following factors may preclude an awake craniotomy:
- Any condition that causes involuntary movements.
- Poor compliance with healthcare professionals e.g. due to acute confusion and learning difficulties.
- Uncontrollable cough.
- Difficulty lying fat e.g. due to a raised BMI and obstructive sleep
apnoea.
- High anxiety levels.
- Language barrier.
- Take a history of the brain tumour to include the diagnosis, any previous or current symptoms and treatment.

The preoperative assessment should include a detailed neurological history and examination to determine the patient’s preoperative status.

Question 3

What added information would you like prior to proceeding with this case?

Surgical factors?

Answer 3

• Discuss the expected duration of surgery including the likely period of being awake.
• Conduct a multidisciplinary discussion to include the patient suitability for awake neurosurgery and any challenges that may arise.

Question 4

What are the key aspects to prepare for this procedure?

Answer 4

Patient preparation:
* Psychological assessment for an awake procedure.
* Ensure adequate information describing the peri-operative events and
theatre complex.

Anaesthetic preparation:
* Preoperative assessment by an experienced neuroanaesthetist.
* Conduct a multidisciplinary team meeting to discuss specific factors such as the anaesthetic plan, positioning, temperature and noise
levels.

Question 5

What are the options for anaesthesia in this patient?

Answer 5

Awake for the duration of the procedure:
* Use conscious sedation, allowing the patient to maintain spontaneous ventilation and a response to stimuli.
* Agents of choice include propofol, remifentanil, clonidine, dexmedetomidine and benzodiazepines.

Asleep – awake – asleep:
* Induction of general anaesthetic with a target-controlled infusion using propofol and remifentanil. Securing of airway with endotracheal tube or laryngeal mask airway.
* Reduction of anaesthetic agent concentrations during the “awake” period, followed by reintroduction of general anaesthesia for closure.

Asleep/sedated – awake
* As above, but the patient is kept awake for closure.
* In some centres, a general anaesthetic is not required initially.

Question 6

How is a scalp block performed?

Answer 6

• Ensure consent, apply AAGBI monitoring, prepare emergency drugs and equipment and calculate the maximal dose of permitted local anaesthetic to avoid the risk of toxicity.
• A scalp block is performed under sedation or general anaesthetic.
• Use a sterile technique, and conduct a “stop before you block”
  moment.
• Infiltrate local anaesthetic to block specific nerves:
• Supraorbital nerve (at the supraorbital notch).
• Supratrochlear nerve (medial to the supraorbital notch).
• Zygomaticotemporal nerve (at the temporalis muscle).
• Auriculotemporal nerve (anterior to the auricle).
• Lesser occipital nerve (posterior to the auricle).
• Greater occipital nerve (medial to the occipital artery).
• Greater auricular nerve (posterior to the auricle).

Question 7

While the surgeon is carrying out cortical mapping, the patient has a seizure. How do you proceed?

Answer 7

• Alert the theatre team and call for urgent help.
• Ask the surgeons to irrigate the surgical site with ice-cold saline.
• Administer pre-prepared agents for seizure control following a
  discussion with the surgeon.
• Consider deepening sedation or general anaesthetic (with appropriate
  airway management) if seizure control is not achieved with the above measures.

Question 8

What are the known complications associated with an awake craniotomy?

Answer 8

• Loss of the airway/airway obstruction.
• Respiratory depression.
• Aspiration.
• Air embolus.
• Haemodynamic instability.
• Anxiety/lack of compliance peri-operatively.
• Local anaesthetic toxicity.