Awake Craniotomy-Advances in Tumour Treatment

May 01 11:33 2025 Print This Article

Introduction

Tumours can grow in or near important areas of the brain that control vision, movement, and speech. Awake craniotomy (AC) is a type of brain surgery where the patient stays awake during part or all of the procedure. This helps neurosurgeons safely remove the tumour. Unlike traditional brain surgery under general anaesthesia, this method allows surgeons to test brain functions during the operation. This reduces the risk of harming important brain areas and helps remove as much of the tumour as possible.

Pre-operative evaluation

• The ideal candidate for this procedure should be mature, well-motivated, capable of lying still and being cooperative when asked to perform tasks.
• The anaesthesiologist should discuss the rationale and steps of the procedure, describe the expected level of pain and discomfort and indicate the tasks required for testing and possible complications.
• In addition to medical optimization, patients should undergo psychological preparation to relieve anxiety.
• Pre-operative airway evaluation should be conducted for all patients.
• Pre-medication is administered based on the patient’s anxiety levels, co-morbidities, baseline neurological status and anaesthesia plan. Patients undergoing seizure mapping should not receive benzodiazepines as they lower brain activity. Anti-hypertensives, anti-epileptics and steroids can be taken as usual.
• Radiological imaging for surgical planning and motor and speech assessment for obtaining baseline values (2 days before surgery) are conducted.

Basic anaesthetic monitoring include the following parameters: pulse oximetry (oxygen levels), electrocardiography (heart rate and rhythm), end-tidal CO₂ (breathing), temperature and blood pressure and urine output. A processed electroencephalogram (pEEG) also known as Bi-spectral Index (BIS) is used for optimizing the dose of anaesthetic agents and for rapid awakening for intra-operative tasks.

Anaesthesia technique

The choice of the anaesthetic agent is based on the preferences of the surgical team and the anaesthesiologist.

Conscious sedation

The patient is awake throughout the entire procedure (awake-awake-awake). Moderate sedation (low dose of sedatives) is administered to pin the skull, for skin incision and to open the bone flap. Sedation is gradually reduced or stopped for brain mapping and restarted after tumour resection. Moderate sedation avoids a sudden emergence from the asleep state, which can cause delirium and reduce the reliability of the brain mapping procedure. Moderate sedation ensures the patient is responsive to touch or verbal stimulation with competent airway.

The standard protocol of sedation involves a combination of propofol and remifentanil during the first stage as it is easy to use and reliable. It allows easy recovery, rapid consciousness and a smooth transition for intra-operative brain mapping. It is crucial to achieve the optimum level of sedation as excessive sedation can cause respiratory depression (low breathing rate), producing hypercapnia (too much CO₂ in the blood) and brain oedema and less sedation causes patient movement and anxiety. Thus, an experienced anaesthesiologist who can maintain the patient in a state of drowsiness as well as readily responsive state is necessary for the complex setting of AC.

Dexmedetomidine is used as an alternative to propofol as it maintains haemodynamic stability (heart rate and blood pressure are stable), negligible respiratory depression and minimal effect on brain mapping. Inhalation anaesthetics (sevoflurane) are also used but they increase the intracranial pressure and cause nausea and vomiting during the awake phase. It is preferable to avoid inhalational agents in this setting.

General anaesthesia

The anaesthetic is administered either only in the beginning (asleep-awake) or both at the beginning and the end (asleep-awake-asleep) with an intra-operative awakening for brain mapping.

General anaesthesia is induced at the beginning and the airway is secured via endotracheal intubation/laryngeal mask airway (keeps the airways open for air to enter the lungs). Once the dura (located directly underneath the skull bone) is opened, the patient is awakened to participate in brain mapping. After completion of brain mapping and tumour resection, general anaesthesia is induced again to stitch up the scalp. The advantages of this method are the prevention of unintentional patient movements and the control of brain oedema via hyperventilation.

Analgesia

Before securing the skull, a unilateral or bilateral scalp nerve block is performed for effective pain control. Scalp block is performed for haemodynamic stability and to reduce the stress response to pain during the awake phase and patient satisfaction post-surgery. Scalp innervation is performed by infiltrating a local anaesthetic to seven nerves on either side of the scalp.

Brain mapping

After injecting the anaesthetic, the surgeon makes an incision through the scalp to expose the skull. A piece of the skull bone is removed to expose the brain, and brain mapping is used to determine the functional areas. This is followed by tumour resection, and the skull bone is fixed in place and the scalp is stitched up.

Several techniques are used for brain mapping as discussed below:

Direct electrical stimulation (DES)

It is the oldest and most widely employed brain mapping technique. An electric current is used to stimulate the brain’s surface, and the patient’s ability to perform certain tasks is assessed, such as moving certain body parts, reading words on a screen, and naming a few pictures. This helps the neurosurgeon to identify regions involved in movement, language or vision, allowing tumour resection without causing functional impairment. However, it is an invasive method and exposes the cortex beyond the surgical goal to identify and preserve the eloquent area.

Electrocorticography (ECoG)

The electrodes are placed directly on the cortex to detect its electrical discharges. It is used for speech and motor mapping to identify safe regions for epileptic foci resection in children owing to challenges in intra-operative mapping. ECoG has excellent spatial and temporal resolution. However, it is an invasive technique and increases the surgery duration.

Functional Magnetic Resonance Imaging (fMRI)

fMRI tracks the blood flow in different brain regions. Active regions of the brain use more oxygen, which will increase the cerebral blood flow, and the region will appear brighter on the scan. fMRI is non-invasive, safe, quick and less distressing for the patient. It can be safely used in children. It has been used to map the language cortex (tasks include naming pictures, generating verbs and testing grammar) and motor cortex (tapping fingers or clenching hands).

Intra-operative MRI (iMRI)

iMRI provides real-time images of the brain while the neurosurgeon performs the surgery. The real-time image reduces the risk of damaging critical brain regions, identifies additional resection areas and increases the chance of completing the surgery in one sitting. This technique also considers the brain shift during surgery and provides real-time images to avoid errors.

Post-operative care

Post-operative recovery is quicker as general anaesthesia is not usually administered. Food intake and mobility can be initiated when the patient is ready. Patients can go home the same day or the next day of surgery. For the first few weeks, patients may experience headaches, which can be controlled with painkillers. Patients may feel tired and should take ample rest. Walking is good exercise, and patients should be encouraged to do it. The neurosurgeon examines the patient a week after surgery to examine the recovery progress, share biopsy results and suggest further treatment options.

When should AC be performed?

• Tumour resection in areas of the brain performing vitally important functions, such as the motor cortex, language cortex and sensory cortex.
• Electrocorticography to determine the location of the seizure onset zone and resection by minimizing the interference from anaesthesia
• Deep brain stimulation surgery for Parkinson’s disease, Alzheimer’s disease, and other psychiatric and central movement disorders.
• Ventriculostomy (surgery to drain excess cerebrospinal fluid) and stereotactic brain biopsy (procedure to obtain samples of brain lesions)
• Interventional pain procedures such as thalamotomy (surgery to control tremors) and pallidotomy (surgery to treat involuntary movements)

When should AC not be performed?

• Lack of patient cooperation and inability to obey commands of the neurosurgeon for brain function evaluation
• Obese patients
• History of chronic cough, obstructive sleep apnea and difficult airways
• Surgeries involving excessive blood loss
• Patients with anxiety disorders, schizophrenia or low pain tolerance

Benefits of AC 

• Maximizing tumour resection while protecting vital brain functions
• Need for ICU monitoring is reduced, thereby either shortening or eliminating ICU stay
• Risks associated with general anaesthesia, mechanical ventilation (life support that helps in breathing when patients cannot breathe by themselves) and intubation can be avoided
• Reduction in neurological deficits and duration of hospital stay (reduces the risk of hospital-acquired infections or deep vein thrombosis)
• Post-operative pain, vomiting and nausea are reduced

Complications during AC 

• Seizures: The incidence of seizures is approximately 2%–20% and usually occurs during electrical stimulation for brain mapping. Most intra-operative seizures are brief, focal or generalized, and resolve quickly. Patients with a history of seizures are more prone to it. Sterile ice-cold saline is used to irrigate the brain, and if it is ineffective, midazolam (1-2 mg IV) or propofol bolus (10-20 mg IV) is administered.
• Nausea: Nausea occurs in approximately 4% of the cases due to anxiety, opioids or surgical stimulation. Propofol or dexamethasone is administered for nausea management.
• Hypertension: Pain or anxiety can cause hypertension but other causes, including low oxygen levels (hypoxia) or high carbon dioxide levels (hypercarbia) should be assessed.
• Respiratory complications: Excessive sedation can result in airway obstruction, potentially causing hypercarbia or hypoxia.
• Air embolism: The incidence of venous air embolism (entry of gas bubbles in a vein or artery blocking the passage of blood) is approximately 20%-40%.
• Hyponatraemia: This is the most frequently observed electrolyte imbalance in patients undergoing neurosurgery.
• AC is considered unsuccessful if general anaesthesia is required or adequate mapping cannot be achieved. Failed AC occurs in 2% of the cases.

Conclusion

AC with brain mapping is a neurosurgical procedure for tumour resection in or near eloquent brain regions. Direct electrical stimulation is the gold standard for brain mapping, and the awake patient is asked to perform specific tasks related to areas that control movement, language and vision to determine if the stimulus disrupts task execution.

AC maximizes tumour removal while maintaining functional activity, reduces the length of hospitalization, reduces monitoring needs in the ICU and reduces post-operative discomfort, nausea and vomiting.

Patient selection and adequate psychological counselling are essential for the success of AC. Patient cooperation and the ability to follow commands are mandatory for successful brain mapping. Moderate sedation and nerve block are required for the patient to be cooperative, pain-free and comfortable. A multi-disciplinary team comprising an anaesthesiologist, a neurosurgeon, a neurologist, a neurophysiologist,  a psychologist, a physiotherapist and should provide a detailed explanation of the procedure and patient expectations to reduce anxiety and enhance the success rate of the surgery.

For expert consultations and advanced neurosurgical care, visit Kauvery Hospital, with branches in Chennai, Hosur, Salem, Tirunelveli, and Trichy. Our specialists are here to support you.

Frequently Asked Questions

What is awake craniotomy?
An awake craniotomy is a specialized brain surgery where the patient is kept awake during part of the procedure. This allows doctors to monitor brain functions like speech, vision, and movement while removing a tumour safely.

Will I feel pain during an awake craniotomy?
No, you will not feel pain during the surgery. Scalp nerve blocks and mild sedation are used to ensure you are comfortable throughout the procedure.

Why do I need to be awake during the surgery?
Being awake helps the surgical team monitor your brain function in real time. This ensures vital areas related to speech, movement, and senses are not damaged while removing the tumour.

How long does an awake craniotomy take?
The duration varies based on tumour location and complexity but generally takes between 4 to 8 hours.

What are the risks associated with awake craniotomy?
Risks include seizures, nausea, hypertension, respiratory issues, air embolism, and in rare cases, failed brain mapping requiring general anaesthesia.

Can children undergo awake craniotomy?
It is less common in children due to cooperation challenges, but non-invasive mapping like fMRI and ECoG may be used if needed.

Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai (Alwarpet & Vadapalani), Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and pediatric trauma care.

Chennai Alwarpet – 044 4000 6000 •  Chennai Vadapalani – 044 4000 6000 • Trichy – Cantonment – 0431 4077777 • Trichy – Heartcity – 0431 4003500 • Trichy – Tennur – 0431 4022555 • Hosur – 04344 272727 • Salem – 0427 2677777 • Tirunelveli – 0462 4006000 • Bengaluru – 080 6801 6801