Skull-base Surgery
Lesions of the skull base present a unique challenge to neurosurgeons. In fact, there are very few neurosurgeons in the world who are specially trained and highly qualified to perform such intricate surgery in the small recesses of the brain. Dr. Maroon is part of this minority of experienced surgeons. Our neurosurgeon at UPMC also staff have experience in cerebrovascular surgery and perform vascular skull base surgeries. These may involved management of complex vascular and neoplastic (cancer) lesions of the skull base.
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As a patient, the following
information should help you understand the skull base and what
is involved in skull base surgery. Skull-base surgery can be performed
in several ways, depending on the location and type of tumor or
vascular lesion. The information listed below is not intended
to take the place of a physician's explanation, but designed to
answer some common questions and make you familiar with terms
and procedures related to skull-base surgery.
Index of Services and Procedures:
Skull base is the term used to describe the area of the skull
that provides the base on which the brain rests. Contained within
the skull base are the eye orbits, ear canals, two carotid arteries,
two vertebral arteries, 12 cranial nerves and the blood drainage
system of the brain. These many intricate structures make the
skull base one of the most complex areas on which to operate.
What are the cranial nerves
and why are they so important?
There are 12 pairs of cranial nerves. Each pair of nerves is responsible
for a specific, basic function such as blinking, swallowing or
focusing the eyes. One of each pair of cranial nerves provides
feeling and function, or innervates, the right side of the body
and the other nerve in the pair innervates the left. Many tumors
of the skull base can affect the cranial nerves, both by their
presence and by the steps the surgeon must take to remove the
tumor. The result may be a permanent or temporary loss of function
of one or more of the cranial nerves. Your surgeon will be able
to discuss your specific situation with you as well as your risk
of damage to the cranial nerves.
First Cranial Nerve (olfactory nerve) - This nerve is responsible
for smell. If injured by tumor or surgery for tumor removal food
taste is also altered.
Second Cranial Nerve (optic nerve) - This nerve is responsible for vision. A partial injury to this nerve may result is a "field cut" or partial vision loss.
Third, forth, and sixth Cranial Nerves (oculomotor, trochlear, and abducens) - These nerves are used to control movement of the eyeball. Injury can cause double vision. The third also controls pupil dilation.
Fifth Cranial Nerve (trigeminal nerve) - This nerve controls both function and sensation of the face and if damaged can result in difficulty chewing and diminished facial sensation or facial numbness.
Seventh Cranial Nerve (facial nerve) - This nerve controls facial movements. An injury can result in a facial "droop".
Eight Cranial Nerve (auditory or acoustic nerve) - This nerve is responsible for hearing. Skull-base surgery can sometimes leave hearing intact once a tumor on this nerve is removed.
Ninth Cranial Nerve (glossopharyngeal) - This nerve is responsible for sensation to the back of throat.
Tenth Cranial Nerve (vagus nerve) - This nerve protects against choking, and allows for normal swallowing and speech.
Eleventh Cranial Nerve (spinal accessory nerve) - This nerve responsible for shrugging shoulders.
Twelfth Cranial Nerve (hypoglossal nerve) - This nerve is responsible for tongue movement.
Two kinds of disorders may make skull-base surgery necessary for
your patient. The first, vascular lesions, include aneurysms,
malformations of the veins and arteries, and fistulas. The second
are benign and malignant tumors. As you are aware, benign tumors
also may be life-threatening; we will work with you to determine
whether surgical intervention is necessary.
Recent advances in skull-base
surgery
Traditionally,
many tumors at the base of the skull have been inoperable. In
the past, surgical techniques simply were not satisfactory, and
many patients faced a high risk of neurological problems after
surgery.
Advances in diagnostic imaging, surgical techniques and instruments,
and a better understanding of the skull-base anatomy have allowed
neurosurgeons to remove tumors at the base of the skull. Previously
inoperable lesions now may be removed with far fewer risks to
the patient.
Identifying such lesions has become less difficult during the
past few years thanks to the advent of magnetic resonance imaging
and angiography, among other diagnostic tools. Early detection
allows the surgeon to operate sooner and may prevent many complications.
Because most tumors of the skull base are benign, early treatment
is crucial to prevent a malignancy and maintain optimal function
of nerves and arteries in this area.
Reaching the recesses of
the brain
Skull-base surgery involves operating within one of three regions
of the skull: the anterior, middle or posterior fossa. Neurosurgeons
who work within these areas must approach each in a very specific
way with regard to the size and type of lesion to be removed.
Because of the delicate nature of this type of surgery, patients
may be in the operating suite from six to as many as 15 hours
or more.
The
anterior fossa(green section on drawing)
Meningiomas are the most common types of tumors found in this
region of the skull base. This benign tumor commonly extends through
the skull-base bone and down into the bones of the face. Other
types of tumors commonly found in the anterior fossa are pituitary
and olfactory lesions, and aneurysms.
To reach such tumors, the neurosurgeon may be required to gently
retract the brain from the skull base, allowing removal of the
tumor and nearby bone. On occasion, surgeons must use transorbital,
transfrontal or transsphenoidal routes to expose and remove the
tumor mass.
The middle fossa(blue section on drawing)
The middle fossa of the brain may be approached transtemporally,
subtemporally, transfrontally, pterionally or transsphenoidally.
The surgical team at ANI's Center for Skull-base Surgery often
will include both a neurosurgeon and otolaryngologist to operate
within the complicated anatomy of this region of the skull base.
The posterior fossa(gray section on drawing)
Neurosurgeons often reach lesions in this area of the skull base
through the mastoid region and/or labyrinth of the ear. As such,
the base of the skull and posterior fossa are clearly exposed
to aid in removing lesions within this area. The posterior fossa
also may be approached transorally - by way of the roof of the
mouth - to gain access to the skull base.
Located in the midportion of the brain, the cavernous sinus houses
the carotid artery and multiple cranial nerves. In this small
but extremely complex region, it was once virtually impossible
to remove lesions. Largely in part due to advanced surgical techniques,
extensive experience, specific anatomic knowledge and specialized
instrumentation, successful surgery within the cavernous sinus
now is possible. The neurosurgeons at ANI's Center for Skull-base
Surgery collectively have a large pool of experience with surgical treatment of cavernous sinus pathologies.
Certainly one of the key aspects of skull-base surgery is reconstructing
the skull base after a tumor has been successfully removed or
aneurysm has been clipped. Again, it is imperative that the breadth
of expertise is vast among surgeons performing these delicate
procedures; there must be no chance that the brain will herniate
into the nose or surgical cavities or the cerebrospinal fluid
does not leak. Often, reconstruction may require taking tissue
from another part of the body to create planes and form a successful
sealant. Bone from other parts of the skull also may be used in
reconstruction procedures.
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© 2008 Tri-State Neurosurgical Associates - UPMC
Last Updated: January 1, 2008