Skull Base Surgery Program

Skull base surgery refers to surgical techniques required to obtain access to the floor of the cranial cavity. Due to the complexity of this region, the neurosurgeon often works in conjunction with ear, nose, and throat (ENT), or plastic surgeons when performing skull base surgery because of the close proximity of the face and neck to the skull base. Advances in microsurgical techniques, understanding of the skull base anatomy, improvements in neuroimaging, endoscopy, and stereotactic radiosurgery have allowed such lesions to be successfully treated.

Anatomy of the skull base

The skull base is composed of the bones and cartilage that form the face and cranium which surrounds the bottom of the brain. The bones of the skull base also form the eye socket, rood of the nasal cavity, some of the sinuses, and the inner ear. Contained within this region are major blood vessels that supply the brain with essential nutrients and important nerves with their exiting pathways. The floor of the skull is divided into three regions from front to back: the anterior, the middle, and the posterior compartments. The anterior compartment is the region above a person’s eyes and some of the sinuses, the middle compartment is the region behind the eyes and centered around the pituitary gland, an organ required for proper hormonal function. The posterior compartment contains the brainstem and the cerebellum and is centered around the inner ear and the connection of the brain to the spinal column. The brainstem is the connection between the brain and spinal cord, containing the origin of nerves involved in the control of breathing, blood pressure, eye movements, swallowing, etc.

Symptoms

The symptoms and presentation of patients with tumors and conditions of the skull base is highly variable because of the many important structures contained in this area. These symptoms occur due to direct compression of important nerves by a tumor or blood vessels or by blocking the normal flow of fluid around the brain. Tumors of the anterior compartment may produce headache, sinus congestion, or vision changes. Those of the middle compartment may produce endocrine dysfunction or vision changes. Those of the posterior compartment can produce neck pain, dizziness, tinnitus, hearing loss, and difficulties with swallowing and talking.

Diagnosis

The diagnosis of growths or abnormalities that may require skull base surgery is based on your symptoms and a physical exam. Imaging studies are an important component of the diagnosis of skull base conditions because this area cannot be seen directly. Brain imaging studies such as magnetic resonance imaging (MRI) and Computed tomography (CT) scans are often used. In some cases, neurological surgeons may employ an MRI or CT scan with frameless stereotactic guidance for preoperative planning purposes. For this study, a high-resolution contrast MRI or CT is performed and then processed by a computer to create a three-dimensional model of the brain and skull base. This can be used in the operating room when performing endoscopic minimally invasive skull base surgery. Special tests such as PET scan, MRA and angiography are sometimes used to help your medical team better see a growth or abnormality and identify its blood supply. If the conditions involves the sinuses or if surgery will traverse the sinuses endoscopy of the sinuses may be performed before surgery by the ENT specialist to evaluate your particular anatomy. Other tests such as balance, vision, and hearing evaluations may also be checked.

Skull base surgery can be done in two main ways. Although the preferred method is endoscopic, open surgery is also an option, depending on the type of growth that needs to be removed and its location:

Endoscopic or Minimally Invasive Skull Base Surgery

An ENT surgeon usually helps approach the tumor through the nose (endonasal) and natural sinuses and together with the neurosurgeon they remove the tumor through a thin tube with a light source at the end called an endoscope. Endoscopic techniques continue to evolve and requires careful analysis by your surgeon to determine if you are a candidate.

Traditional or Open Skull Base Surgery

This type of surgery generally requires an incision behind the hairline and opening of the skull. Advances in neuro-anesthesia and microsurgical techniques (typically an operating microscope is used) have made this surgery safer and less invasive. In this type of surgery, bone surrounding the skull base is removed so that the surgeon can access the skull base with minimal to no brain retraction at all which leads to better outcomes. The bone that is removed is reconstructed at the end of the operation. In some cases this surgery is performed with minimally invasive techniques and combined with an endoscope, which allows for smaller incisions and even surgery through an eye-brow or eyelid incision.

Surgery for Skull Base Tumors and Conditions

The management of skull base tumors and conditions often requires consideration of several factors including the patient’s symptoms, growth of a lesion over time, the suspected pathology and potential for post-operative chemotherapy or radiation. Depending on the particular location and structures involved specialists in ENT, ophthalmology, radiation oncology and medical oncology may need to be involved. Some patients are candidates for non-invasive stereotactic radiosurgery and other patients may benefit from either open or endoscopic surgery. The diversity of skull base tumors and conditions are vast, and they may arise from various sources including the brain, the lining of the brain, the bones making up the skull base, or metastases. Although these tumors and conditions have unique individual characteristics, they may present in a similar fashion due to involvement of similar nervous structures. They can be grouped according to the area of the skull base from which they arise:

Tumors and conditions occurring in the anterior compartment include:

• meningiomas
• estheisoneuroblastomas (olfactory neuroblastoma)
• orbital gliomas
• nasopharyngeal carcinomas
• juvenile nasopharyngeal angiofibroma
• encephaloceles

Those occurring in the middle compartment include:

• meningiomas
• pituitary adenomas
• Rathke’s cleft cysts
• craniopharyngiomas
• schwannomas
• cholesteatoma
• encephaloceles

Those of the posterior compartment include:

• acoustic neuromas
• schwannomas
• epidermoid tumors
• chordomas
• chondrosarcomas
• Glomus tumors
• Trigeminal neuralgia
• Hemi-facial spasm