What is a craniotomy?

A Craniotomy is a surgical procedure to remove a small section of the skull (creating a bone flap) to gain access to the brain. The bone flap is removed during the operation and replaced afterwards.

There are different types of craniotomy that are usually named after the bone in the skull being removed or for smaller sections. This can get a little complicated for a procedure with a relatively straightforward purpose, so for an introductory post, let’s explain that purpose first.

Why use a craniotomy?

A craniotomy is the work horse of the neurosurgeon and is the main way that we access the brain. A craniotomy usually needs to be done for the following disease processes:

• Aneurysms
• Brain tumours
• Artero-venous malformations
• Brain abscesses
• Trauma

What happens before surgery?

Before the surgery, a surgeon will come to see you and get a consent form signed. They will explain the procedure, including any side effects or complications and answer any questions you may have. An anaesthetist will also see you; they are the person that puts you to sleep and looks after you during the operation. The exception to this is if you need a craniotomy due to trauma. At this point a decision to perform surgery is usually made in a patient’s best interests.

What happens during a craniotomy?

Once anaesthetised a small amount of hair is removed from your scalp. The patient will be held in place using a 3-pin skull fixation device (Mayfield clamp – your head is literally held by 3 pins). Then a team member will:

• Use an antiseptic to clean the scalp
• Inject a local anaesthetic into your scalp to reduce pain after the surgery
• Drill a small number of burr holes into the skull and then use a drill to cut between the holes forming a bone flap
• Remove the bone flap to access the brain
• Replace the section of bone after surgery is completed
• Fix the bone piece with metal clips and suture (tie) the skin edges together
• Insert a wound drain- to prevent collection of fluid or build-up of pressure within the skull
  

An important exception

Though most craniotomies are done under general anaesthetic, it is sometimes useful to wake the patient to assess the immediate impact of the surgery on their neurological functions.

Awake craniotomies are mostly used for the removal of brain tumours. When a tumour is near a part of the brain that controls core functions: speech, language or movement – what we call ‘eloquent’ regions – waking the patient is the best way to detect and preserve these functions without removing the wrong tissue.

You might think this is barbaric, but the patient doesn’t actually feel what is going on inside the brain as it has no pain receptors.

In terms of how function is neurologically assessed, the neurosurgeon will often stimulate part of the brain near the tumour by sending a light electrical current down the nerves. At the same time, the neuro-anaesthetist will often give the patient simple tasks to see if the stimulation affects various neurological functions. For instance, one could test speech by asking the patient to name an object on a flash card.

What happens after a craniotomy?

Following a craniotomy a patient will have frequent observations carried out by someone with experience caring for those following a neurosurgical procedure.

These will include checking your conscious level (following some simple commands), pupil examination (shine a light in your eyes), test the muscle response and limb strength, blood pressure, pulse, temperature and breathing. It usually takes a few days for people to be discharged.

Are there any complications?

As with any operation, there are risks and complications that may occur. During the consenting process, the surgeon will speak to you about the specific risks with your procedure.

Examples of complications can broadly be broken down into neurological and general medical:

Neurological:

• Temporary or permanent neurological deficit (stroke e.g. paralysis of limbs or loss of speech)
• Haematoma (blood clot)
• Brain swelling
• Infection
• Fits
• Muscle weakness
• CSF leak (leakage of fluid from around the brain)

Medical:

• Deep vein thrombosis (clot in leg veins – DVT)
• Pulmonary embolism (clot from legs passing to lungs – PE)
• Pneumonia
• Heart attack
• Urinary tract infection (due to catheterisation being a requirement for any operation over 2 hours)

It should be noted that, reassuringly, the chances of getting serious and disabling neurological deficits such as stroke are comfortably less than 5%.

Summary

A Craniotomy is a neurosurgical procedure that allows access to the brain through a small section of removed bone. Awake craniotomy is used for mapping out areas that can be safely removed while assessing function in real time. The patient undergoing a craniotomy will be spoken to by the surgeon before the operation and told about risk and complications that can occur (as with any operation).

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