The skull is made up of bones and cartilage that form the face and the cranium, which surrounds the brain. You can feel the bones of the cranium on top of the skull. The 5 bones that form the bottom (base) of the cranium also form the eye socket, roof of the nasal cavity, some of the sinuses, and the bones around the inner ear. The skull base is a crowded and complex area with different openings. The spinal cord, many blood vessels, and nerves pass through these openings.

Skull base surgery may be done to remove both noncancer and cancer growths, and abnormalities on the underside of the brain, the skull base, or the top few bones (vertebrae) of the spinal column. This is area is hard to see and reach. Because of this, surgery may be done by a minimally invasive endoscopic procedure. In this procedure, the surgeon may insert tools through the nose or mouth. Or they may make a small hole just above the eyebrow and insert the tools there. This type of surgery needs a team of specialists. These may include ear, nose, and throat surgeons (ENT or otolaryngologist), maxillofacial surgeons, plastic surgeons, neurosurgeons, and radiologists.

Before endoscopic skull base surgery, the only way to remove growths in this part of the body was by making an opening in the skull. In some cases, that type of surgery may be needed.

What is skull base surgery used for?

These are some of the growths and conditions that may be treated by skull base surgery:

• Cysts that develop from birth

• Growths caused by infections

• Pituitary tumors

• Meningiomas, noncancer tumors that grow from the tissue that covers the brain and lies between the brain and skull (the meninges)

• Chordomas, a slow-growing bone tumor most often found at the base of the skull

• Trigeminal neuralgia, an intense nerve pain on 1 side of the face

• Craniopharyngiomas, growths that occur near the pituitary gland

• Craniosynostosis, a condition in which the bones of an infant's skull fuse too early. This causes problems with brain growth and the shape of the skull.

• Cerebrospinal fluid fistulas are leaks of clear fluid. If not treated it can lead to recurrent meningitis.

• Cerebral aneurysm, a weak, often bulging area in a blood vessel under the brain

• Arteriovenous malformations, arteries, and veins that are abnormally connected to one another

Types of skull base surgery

Skull base surgery can be done in 2 main ways. The preferred method is endoscopic surgery. But open surgery is also a choice. This will depend on the type of growth that needs to be removed and its location:

• Endoscopic or minimally invasive skull base surgery. This type of surgery often doesn't need a large cut (incision). A surgeon may make a small opening (keyhole) inside the nose. The neurosurgeon can then remove a growth through a thin lighted tube called an endoscope. An MRI is a type of picture taken of the skull base using magnets, coils, and a computer. An MRI may be done by a radiology specialist while the surgical specialists are operating. This helps them make sure all of the growth has been removed.

• Traditional or open skull base surgery. This type of surgery may require incisions in the facial area and in the skull. Parts of bone may need to be removed so that the growth can be reached and removed. An operating room microscope is often used for this type of surgery.

Symptoms

You may have many possible symptoms from a growth or abnormality in the skull base area. Symptoms will depend on the size, type, and location of the growth or abnormality. They may include:

• Facial pain

• Headache

• Dizziness

• Vision problems

• Numbness

• Weakness of the face

• Hearing loss or ringing in the ears

• Stuffy nose or frequent sinus infections

• Hormonal disorder

Diagnosis

The diagnosis of growths or abnormalities that may need skull base surgery is based on your symptoms and a physical exam. Because this area can't be seen directly, these exams and imaging studies are important parts of the diagnosis:

• Brain imaging studies. Special tests to create pictures of the skull. This helps your medical team see a growth or abnormality. These tests include MRI, MRA (magnetic resonance angiogram), PET (positron emission tomography), and CT scans.

• Biopsy. A small piece of a growth in the skull base may be taken out and looked at under a microscope. A biopsy may be done using an endoscope placed through the nose and sinuses. Biopsies may also be done by fine needle aspiration.

• Other tests. Your balance, cranial nerves, muscle activity, vision, hearing, and hormonal levels may all be checked. Studies or scans of other areas and body systems may also be checked.

Treatment

In addition to endoscopic and open skull base surgery, these treatments may be needed. This will depend on the type of growth or abnormality of the skull base:

• Chemotherapy. These are medicines used to treat growths caused by cancer.

• Radiation therapy. X-ray treatment may be used to control a growth in the skull base that can't be completely removed by surgery.

• Gamma knife or radiosurgery. This is a special type of radiation therapy that uses a large number of precise X-ray beams to target a growth in the skull base.

• Proton beam therapy. This is another type of radiation therapy. It's designed to have greater accuracy and dosing for tumors.

• Particle therapy. This is the newest form of radiotherapy. It uses high-energy particles with fewer side effects. Carbon-ion radiotherapy is a form of particle therapy.

• Endocrine therapy. This uses medicines to increase or decrease certain hormones.

• Immunotherapy. These medicines stimulate the immune system to target and remove tumor cells.

Managing after skull base surgery

After skull base surgery, you will be closely cared for by your medical team. Their goal is to allow you to go back to your normal activities of daily living. Some people need continued therapy. This may include radiotherapy, radiosurgery, and proton beam therapy. Many will need repeated imaging to make sure that a growth is not coming back over time. Both the early symptoms and this type of surgery can be very stressful. So it's also important to get support from friends and family. Your treatment team can also provide mental health and support group resources for you and your family.