Advanced Skull Base Surgical Techniques: Minimally Invasive Surgery and Keyhole Surgery

30 March 2022

The skull base located on the lower side of the brain can be divided into the anterior and posterior parts, and is a crowded and complex area where the spinal cord, nerves and blood vessels pass through different openings.

With the widespread use of minimally invasive surgery or keyhole surgery in skull base surgery, patients can avoid open surgery, reducing trauma and pain while significantly shortening surgery time.

Dr Johan Quah Boon Leong, Consultant Neurosurgeon at Sunway Medical Centre, Sunway City said that traditional skull base surgery requires an incision in the skull to examine the skull base and perform surgery.

He added that with advances in medical technology, skull base surgery is now performed with an endoscope, especially through the use of the nasal endoscope which allows surgery to be performed through the body’s natural openings or through small incisions without leaving large wounds or scars.

The nasal endoscope has a camera and light that can be used to reach the base of the skull through the nose to treat a variety of tumours, while small incisions can be made in areas that cannot be reached through the nose and the endoscope is used to operate.

“The endoscope magnifies the target area, giving a wide and clear view, reduces patient trauma and pain, shortens operation time and minimises damage to normal tissues,” he said.

Complex skull base surgery

Dr Quah said that most skull base surgeries treat tumours, the most common being the pituitary tumour that grows in the pituitary gland and accounts for 10% of head tumours.

However, he pointed out that some skull base surgeries are complex such as meningiomas and craniopharyngiomas which occur mostly in children and adolescents and require a combination of transnasal endoscopy and craniotomy as the tumour is large and may be adherent to some brain tissue.

“Because of the complexity of the procedure, surgery can sometimes take up to 8 to 12 hours,” he said.

Another common type of tumour that originates from the nerve that provides hearing is the vestibular schwannoma. However, Dr Quah noted that thankfully, 90% of skull base tumours are benign or non-cancerous and can be managed well with surgery and radiation therapy, sometimes with just constant monitoring.

“Yet, the few malignant or cancerous tumours are complex and difficult to cure, and usually require a combination of surgical and radiation therapy to manage it,” he said.

Radiation therapy is highly accurate

Gamma Knife radiotherapy is one of the non-craniotomy treatments used to treat tumours at the base of the skull, Dr Quah says.

Gamma Knife is highly accurate in treating tumours smaller than 2.5cm inside the head and most cases of pituitary tumours and auditory neuromas respond positively to this treatment.

“Gamma Knife is mainly used for small, non-major tumours to inhibit their growth. The advantage is that patients do not need surgery and there are no incisions. Some tumours can be treated accurately and effectively with a very low chance of sequelae, if used correctly,” he explained.

Another advantage of the Gamma Knife is that it can treat tumours in different locations at the same time such as small tumours on the left and right side which can be treated at one go.

Doctors will assess which treatment is appropriate based on a variety of factors including the size of the tumour, where it is growing, the patient’s age and needs, and tailor the treatment to the patient.

“If the tumour if too large or located in such a way that minimally invasive surgery is not possible then traditional craniotomy will be the used,” he said.

Intracranial tumours to be considered for smell loss

Although some skull base surgeries use minimally invasive techniques, they are still considered major surgeries as the skull base is full of blood vessels and large and small nerves that connect the brain to the entire body, making it a ‘busy’ area.

“Because it is an area where a lot of important tissues pass through, the risks associated with skull base surgery such as bleeding, stroke, paralysis, visual and auditory impairment are higher than those associated with any other neurosurgery,” he said.

The risks of skull base surgery depend on the type and location of the tumour and the patient’s condition. Patients can discuss their risks with their neurosurgeons.

When it comes to symptoms of skull base tumour, Dr Quah said they generally depend on the location of the tumour. If it is in the anterior skull base, patients usually experience problems with smell, vision and eye movement. Some patients face uncoordinated body movements and the inability to speak normally.

Most of these symptoms are not sudden but rather slow and progressive, and patients often do not seek medical attention until the situation is severe or unbearable.

“It takes time to detect these problems, especially in older people, who think that walking and imbalance are due to old age so they don’t go for tests until it gets worse, even if they haven’t improved for years,” he said.

With the ease of today’s magnetic resonance imaging (MRI), more and more patients are discovering problems at the base of the skull when they are being checked for other medical conditions.

Surgery time depends on complexity

Prior to surgery, the surgeon will consult with the patient including taking a medical history and doing a physical examination including MRI and CT scans.

Depending on the location of the tumour, other tests will be carried out, such as checking the patient’s hormone levels if it is a pituitary tumour, referring the patient to an Ear, Nose and Throat Surgeon for an assessment if there is an ear problem, or an ophthalmologist for eye problems.

The length of the operation depends on the difficulty and complexity of the procedure, ranging from and hour to 12 to 20 hours

Recovery time can be up to six weeks

Dr Quah said that recovery after skull base surgery depends on the patient but if all goes well, patients can return to work 6 weeks after surgery. Most neurosurgeries for pituitary tumours or any brain surgery, most skin wounds heal after a week and patients are discharged after 7 days.

“Some lockjaw surgeries have a faster recovery time, with patients being discharged home in 3 days and a recovery period of only 1 to 2 weeks while larger tumours require a longer recovery period,” he said.

Conditions that require skull base surgery due to abnormalities in the skull base are as follows:

Anterior skull base: Meningiomas, pituitary tumours, olfactory neuroblastoma, paranasal sinus cancer, craniopharyngiomas and Rathke's cleft cyst.

Posterior skull base: Vestibular schwannoma, chondrosarcoma, chordoma, epidermoid tumour and meningioma.

Other conditions that may require skull base surgery: Brain aneurysms, microvascular decompression of cranial nerves, encephaloceles and fibrous dysplasia. 

Source: Sin Chew Sabah