What is Skull Base Surgery?

The term ‘skull base’ is used to designate the areas located on the other side of the roof of the sinuses, extending from the roof of the nose, between the eyes, beyond the roof of the mouth & the backside of the nose where the adenoids are usually located.

A ‘rhinologist’ is an ENT who has completed additional fellowship training in advanced surgery of the sinuses which may include skull base surgery. A fellowship-training in rhinology & skull base surgery includes both of the above subspecialty capabilities.

In the surgical lingo, the skull base is divided into anterior and posterior skull base. The descriptions given above all pertain to the anterior skull base. Examples of cases include surgery for benign and malignant tumors that may extend to adjacent structures, including eyes, sinuses, back of the nose, numerous nerves, arteries/vessels, and the front and mid segments of the brain (as it’s just on the other side of the roof of the sinuses). A pituitary tumor is considered a tumor involving the anterior skull base.

Fig. 1

The lateral skull base mainly encompasses the areas involving the inner ear.

More than 90% of skull base surgery is performed for anterior skull base region as it covers more structures and a variety of tumors seem to like this region more. A skull base surgeon may be either an ENT (otolaryngologist) or a neurosurgeon. For an ENT surgeon to also be considered a skull base surgeon, he/she must be fellowship trained either in rhinology/anterior skull base or neurotology/lateral skull base.
The majority of the practice and clinical focus of rhinology is dedicated to the treatment of benign and malignant tumors involving the nose, sinuses and the structures adjacent to these areas, such as certain areas of the brain, eyes, tear ducts and the jaw. Additionally, rhinologists perform various types of surgery for common diseases involving the sinuses, such as sinusitis with polyps or fungal sinusitis.

For tumors involving the distant corners of the sinus cavities, and the various areas of the anterior skull base, instrumentation and dependence on the cutting-edge technology is crucial in order to allow adequate access to the tumors for manipulation and removal. Because of the difficult access to this region, a variety of techniques are used to reach such tumors. Sometimes open incisions, also called ‘craniofacial’ approaches must be used to gain such access to perform the necessary surgery. Such surgeries are often solely performed by the ENT (otolaryngologist), as such tumors are often within the confines of the ears/nose and may extend to the back of the throat.

Fig 2.

Art drawing showing access to the anterior skull base structures by way of the nostril using an endoscope.

Skull base surgery cases are often performed by a team of surgeons, often including ENT and neurosurgery, and sometimes plastic surgery.

Each member plays an equally significant role. The ENT surgeon is often tasked with providing access to the tumor. On the other hand, in some cases, the neurosurgeon will be tasked with providing access via a craniotomy approach to get to some types of sinus/nasal tumors that have extensive involvement past their normal confines. In the case of pituitary surgery, the ENT will provide access: Essentially a purposeful hole from the roof of the sinuses to the brain. Remember that the nose/sinus is NOT sterile and the brain IS sterile. After the tumor is removed by neurosurgeon, the ENT then is tasked with closing this ‘hole’ between the nose and the brain cavity. The techniques that are used to close this connection is very important, because if it remained open or an unsuccessful closure may lead to brain fluid leak or meningitis.

Fig 3.

Typical arrangements in the operating room for a skull base tumor resection via endoscopic endonasal route.

The surgical treatment of skull base tumors carries a very high risk of possible adverse outcomes, due to the presence of so many important structures in the region, which often fall in the vicinity of the tumor in focus. This includes structures such as the carotid artery, the eyeball, jugular vein, and various nerves for movement and sensation. Therefore, treatment of such conditions requires a highly skilled team. The core of this team must be a fellowship-trained ENT in rhinology and/or neurotology, and a neurosurgeon trained in neuro-oncologic or skull base surgery. Additionally, the team must include highly skilled healthcare staff, ranging from OR technicians and nursing staff with focused knowledge of the preoperative, operative and postoperative care of such patients. Additionally, highly technical and specialized instrumentation and equipment is required to perform such cases. Given these requirements, such a skull base team is often rare, and usually found in academic institutions in large metropolitan regions.

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