Craniotomy: Types, Indication, Procedures, and Recovery

19 September,2024

The brain is the most complex vital organ in the human body. It is housed inside the skull and suspended in the cerebrospinal fluid. Any physical abnormality in the brain, including an injury, a tumor, or a clot, can be detrimental. These conditions need to be treated surgically. Some examples of brain surgery are craniotomy, biopsy, minimally invasive endonasal endoscopic surgery, minimally invasive neuro endoscopy, and deep brain stimulation.

A craniotomy is an intricate procedure performed by a neurosurgeon on the skull bones. Its origins can be traced back to another method known as trephination, performed over 2000 years ago. The first craniotomy for therapeutic purposes was done in 1889 by a German physician and self-taught surgeon named Wilhelm Wagner. It formed the basis of the modern surgical technique practiced today. With the introduction of new-age technology and improved sterilization protocols, craniotomy has become one of the most common procedures for the treatment of brain tumors and other brain disorders.

This blog explores the details of craniotomy, including its types, procedures, and the conditions it treats.

What is a Craniotomy?

A craniotomy is a type of brain surgery where a part of the skull bone is removed to create access to the brain for surgical repair. Once the surgery is complete, this part is put back in its place during the same procedure. A craniotomy is usually the procedure of choice to treat conditions such as brain trauma, brain tumors, infections, parasitic lesions, and vascular repair surgeries. It is an elaborate surgical procedure that an expertly trained neurosurgeon must carry out.

What are the Different Types of Craniotomies?

There are several types of craniotomies based on the part of the skull removed or the technology used during surgery. Depending on location, the types of craniotomies are:

Frontal Craniotomy

• Neurosurgeons prefer the frontal approach to a craniotomy when they have to access the frontal lobe of the brain. It can either be unilateral or bilateral.
• The incision is made near the hairline to remove the front of the skull.
• This method treats tumors or lesions in the anterior interhemispheric, third ventricle, and sellar regions, such as craniopharyngiomas and planum sphenoidale meningiomas. It also treats certain frontal lobe tumors and anterior cerebrospinal fluid fistulas.

Temporal Craniotomy

• The skull's temporal bone lies between the eye and ear. In a temporal craniotomy, bone is removed from this part of the skull.
• In this method, the surgeon makes a linear or question mark incision.
• A temporal craniotomy gives access to the middle cranial fossa and anterior superior brainstem.
• It treats conditions such as petroclival lesions, basilar aneurysms, and trigeminal lesions.

Parietal Craniotomy

• In a parietal craniotomy, the bone is removed from the top of the skull near the center.
• This method exposes the brain's mid to posterior cerebral hemisphere while excluding the motor and sensory cortices.
• Interhemispheric and transcortical are two approaches for a parietal craniotomy.
• It treats meningiomas, metastases, vascular malformations, and gliomas in the exposed area.

Pterional Craniotomy

• The pterion is an H-shaped area on the skull that marks the junction of four skull bones: the frontal, parietal, temporal, and sphenoid.
• This area is found on the side of the head, and the procedure where a part of the pterion is removed for surgery is known as pterional craniotomy. It is also known as frontotemporal craniotomy.
• For this method, the neurosurgeon makes an incision just behind the patient's hairline.
• It exposes the front and center of the skull base, where structures such as the optic nerve, temporal lobe, frontal and temporal operculum, and the Sylvian fissure are seen.
• It treats blood clots, epilepsy, brain aneurysms, brain tumors, and arteriovenous malformations.

Suboccipital Craniotomy

• In a suboccipital craniotomy, the part of the skull that is removed is present at the base of the skull, known as the occipital bone.
• This procedure exposes the posterior fossa of the skull so that the surgeon can visualize brain structures such as the cranial nerves, the cerebellum, the brain stem, and the fourth ventricle.
• A suboccipital craniotomy is of several types: standard, transcondylar, retrosigmoid, and far lateral.
• It treats certain brain tumors, vascular lesions, and Chiari malformation.

Orbitozygomatic (OZ) Craniotomy

• An orbitozygomatic craniotomy involves removing the bone that forms the eye socket and cheek contour.
• The surgeon makes an incision in the scalp behind the patient's hairline.
• An orbitozygomatic craniotomy is further modified into a one-piece or two-piece osteotomy.
• This method allows access to the brain's deeper parts, including the orbital apex, parasellar areas, and cavernous sinuses.
• It treats lesions that are difficult to reach by minimally invasive approaches, such as meningiomas, pituitary tumors, and craniopharyngiomas.

Translabyrinthine Craniotomy

• For a translabyrinthine craniotomy, the neurosurgeon removes a part of the mastoid bone to reach the inner ear. It also involves the removal of the semicircular canals of the ear.
• For this surgery, the surgeon makes an incision behind the ear.
• This method removes a benign ear tumor known as an acoustic neuroma or vestibular schwannoma.
• This approach causes hearing loss in the affected ear. Surgeons typically consider patients with hearing loss for translabyrinthine craniotomy.

Some craniotomy procedures utilize a minimally invasive approach, such as:

• Supraorbital Craniotomy: A supraorbital craniotomy is a minimally invasive technique used to operate on tumors in front of the brain and behind the eyes and nose. The surgeon makes a small incision in the eyebrows through which the cancer is removed. Hence, the procedure is also known as an 'eyebrow' craniotomy. It treats some pituitary tumors, skull base tumors, and Rathke's cleft cysts.
• Retrosigmoid Craniotomy: A retrosigmoid craniotomy, also known as a keyhole craniotomy, is a minimally invasive surgery to expose the cerebellum and brainstem areas. The neurosurgeon makes a small incision behind the ear to access the tumor in that region. This method treats skull base tumors, meningiomas, acoustic neuromas, and metastatic brain tumors.

Depending on the technology used to support the craniotomy procedure, it can be of several types, such as:

• Stereotactic Craniotomy: When diagnostic tests such as magnetic resonance imaging (MRI) or computer tomography (CT) scans are used for a craniotomy, it is known as a stereotactic craniotomy. These tests help the surgeon pinpoint the exact location of the brain that requires treatment and determine the best approach and location to make an incision. They also help differentiate between healthy and diseased brain tissue.
• Endoscopic Craniotomy: An endoscope is a long, thin, tube-like device with a light and camera attached. It is inserted into the brain to perform minimally invasive craniotomies. For an endoscopic craniotomy, the surgeon makes a small incision in the skull to insert the endoscope.
• Awake Craniotomy: In an awake craniotomy, the patient is kept awake during the surgery so that the surgeon can remove a tumor without causing brain damage. Cortical mapping allows the surgeon to monitor the patient's responses and vital functions, such as movement and speech. Thus, the surgeon can operate on the tumor without damaging the brain's functioning areas.

What are the Indications for a Craniotomy?

A neurosurgeon will order a craniotomy to treat several brain tumors, such as meningiomas, gliomas, pituitary tumors, schwannomas, and tumors that have spread to the brain from other body parts. The neurosurgeon may also perform a craniotomy to obtain a tissue sample for tumor diagnosis. Other indications of the procedure are:

• To repair a brain aneurysm, a ballooning, weakened area in a brain's blood vessel.
• To drain brain abscesses (pus-filled pockets) formed due to infection.
• To repair skull fractures, brain contusions, hematomas, and cerebrospinal fluid (CSF) leaks due to trauma to the brain.
• To control bleeding in the brain, known as hemorrhage.
• To remove blood clots in the brain.
• To relieve pressure in the brain (intracranial pressure) caused by swelling due to injury or stroke.
• To correct abnormal connections between arteries and veins, known as arteriovenous fistulas (AVFs)
• To treat tangled blood vessels, known as arteriovenous malformation (AVM).
• To repair tears in the lining membrane of the brain (dura mater).
• For treatment of epilepsy.
• For implantation of devices such as subdural electrodes, shunts, Ommaya reservoirs, and stimulator devices for Parkinson's disease.

What Happens Before the Craniotomy Surgery?

Before the surgery, the neurosurgeon will explain the procedure to the patient. The patient will also undergo some tests to determine their overall health. These tests will also help determine the craniotomy approach and the dose of anesthetic. The required tests include - 

• Blood tests
• Physical exam
• Neurologic examination
• Imaging tests, including X-rays, MRI, CT, and PET scans.

The patient must not eat anything on the day of the surgery. Any additional medicines, such as antibiotics or anticonvulsants, must be taken the day before the surgery.

If the patient is on any blood thinning medication, such as aspirin, the doctor will ask to stop it a few days before surgery.

What is the Procedure for a Craniotomy?

• During the craniotomy surgery, an anesthesiologist will administer general anesthesia to the patient. Once the anesthesia takes effect, the surgeon adjusts the patient's head position to the chosen craniotomy approach.
• The surgeon shaves off any hair present near the incision site and sterilizes the incision site.
• An incision is made in the scalp, and any underlying structures are reflected to expose the bone.
• The skull bone is then removed by drilling holes and making cuts between them. The bone thus removed is stored until the end of the surgery.
• When the desired brain area is exposed, the surgeon will perform the surgery as needed.
• Once the surgery is completed, the bone removed earlier and the surrounding structures are put back in place, and the incision is closed.

What is the Recovery Process After a Craniotomy?

• Immediately after the surgery, the patient is moved to an intensive care unit (ICU), and the doctor will constantly monitor their vitals.
• Once the patient is deemed stable, they are shifted to a hospital room for the rest of their stay.
• After the patient is discharged, the doctor will give a particular set of instructions for recovery.
• Post-surgery, the patient might need to undergo physiotherapy, occupational therapy, or speech therapy to regain vital functions such as walking, talking, balance, and strength.
• Recovery from surgery may take up to several weeks. During this time, the patient is advised to rest heavily.

What are the Risks Associated with Craniotomy?

Like any other surgery, a craniotomy comes with several risks and complications. Some rare complications of a craniotomy include speech difficulties, loss of coordination and balance, difficulty walking, behavioral changes, memory problems, paralysis, and coma.

Some other risks involved with craniotomy are: 

• Infection
• Blood clots
• Bleeding
• Seizures
• Stroke
• Collection of fluid in the brain cavities (hydrocephalus)
• Facial nerve damage
• Cerebrospinal fluid (CSF) leak
• Swelling in the brain
• Pneumonia
• Muscle weakness

Side effects of the procedure depend on several factors, such as the patient's age and overall health, severity of the disease, type of craniotomy, and location of the lesion on the brain.

How is a Craniotomy Different from a Craniectomy?

In a craniotomy procedure, the surgeon removes the skull bone to expose the brain. However, the bone is immediately placed back in place once the surgery is complete. For a craniectomy, the procedure to remove the bone is similar to a craniotomy. The difference is that the bone is not immediately put back after surgery. It is saved to be placed back later, or the surgeon may use an artificial bone. The surgery where the skull bone is replaced is known as cranioplasty.

Key Takeaway

A craniotomy is a standard procedure to treat brain conditions such as tumors and aneurysms. There are several types and approaches to craniotomy. Patients experiencing symptoms of brain disorders can consult a neurosurgeon to determine the best strategy for them. While a craniotomy is a complex procedure and comes with several risks, new-age treatment options are being continuously developed to minimize the risk factors and improve the outcome of the surgery.