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Endoscopic Access to the Infratemporal Fossa and Skull Base
A Cadaveric Study
Christopher J. Hartnick, MD;
John S. Myseros, MD;
Charles M. Myer III, MD
Arch Otolaryngol Head Neck Surg. 2001;127:1325-1327.
ABSTRACT
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Objectives To demonstrate that the regions of the infratemporal fossa and skull
base at the level of the foramen ovale can be visualized endoscopically and
that structures can be manipulated within these regions using endoscopic instruments.
Methods Cadaveric dissection of 3 human cadavers using an endoscopic optical
dissector. In all, 6 endoscopic infratemporal fossa and skull base approaches
were performed.
Setting Human temporal bone laboratory.
Results A Gillies incision was coupled with a lateral brow incision, and then
subperiosteal planes were developed. Endoscopic visualization and instrumentation
was then performed. The infratemporal fossa was readily identified. The skull
base at the level of the foramen ovale and the branches of the third division
of the trigeminal nerve were seen distinctly. A probe was placed with ease
within the foramen ovale itself.
Conclusions Endoscopic access to the infratemporal fossa is readily accomplished,
with excellent visualization and instrumentation ability. This novel technique
provides access to this remote region for evaluation, possible biopsy, and
potential treatment of infratemporal fossa lesions.
INTRODUCTION
THE INFRATEMPORAL fossa is a relatively remote region beneath the skull
base. Access to this region requires thorough knowledge of the anatomy of
the region itself and of the surrounding structures. Surgical procedures to
gain access to this region have been well described by Fisch1-4
and Sekhar5-6 and their colleagues,
among others; these procedures are major surgical endeavors that require precision
and planning.
The anatomy of the infratemporal fossa was well described by Grant7 in 1972. The superior border is composed of the greater
wing of the sphenoid bone and the temporal fossa containing the temporalis
muscle, and the medial border is formed by the lateral pterygoid plate. The
infratemporal fossa is bounded laterally by the mandibular ramus, extends
anteriorly to the posterior wall of the maxillary sinus, and opens inferiorly
into the parapharyngeal space.
A host of neoplasms can either arise from or extend into the infratemporal
fossa.8 Specific to the realm of pediatric
otolaryngology, neoplasms found in this region can include rhabdomyosarcoma,
lymphoma, and juvenile nasopharyngeal angiofibroma. Many of these tumors can
undergo biopsy at some other, more readily accessible area, or the diagnosis
is secured using imaging studies (computed tomography or magnetic resonance
imaging). For a small subset of infratemporal masses, biopsy results before
a major operative procedure might prove useful in guiding management.
This study arises from preliminary work9
in which endoscopic access was gained to the region of the infratemporal fossa
to facilitate diagnosis of a cerebrospinal fluid leak at the region of the
foramen ovale. Having gained access to visualize this region, the question
arises whether this region can be accessed endoscopically such that manipulations
such as biopsies can be performed safely without injuring neighboring structures.
This study presents initial cadaveric dissections that demonstrate such an
ability.
MATERIALS AND METHODS
Three fresh frozen cadaver heads were used for the dissections, which
took place in the Temporal Bone Laboratory, Department of Otolaryngology–Head
and Neck Surgery, University of Cincinnati, Cincinnati, Ohio. The infratemporal
fossa was endoscopically identified on both sides of each head, for a total
of 6 dissections. On 2 dissections, the zygomatic arch was removed after the
endoscopic approach was performed to confirm the anatomical features that
had been visualized endoscopically. A craniotomy was then performed on this
cadaver head to further confirm the identification of the foramen ovale.
The endoscopic approach proceeded as follows. Two separate 2-cm incisions
were made (one at the lateral rim and one just anterior to the temporal hairline)
and carried down through the pericranium (Figure 1). An optical dissector with a distal spatula (Karl Storz
Endoscopy-America Inc, Culver City, Calif) was placed through one incision,
and a suction catheter (Karl Storz Endoscopy-America Inc) was placed in the
other (Figure 2). Using endoscopic
periosteal elevators and the suction freer elevator, the perisosteum was elevated
to the level of the zygomatic arch, which was palpated using the endoscopic
instruments (Figure 3). Inferiorly,
subperiosteal elevation was performed to the region of the infratemporal fossa.
Once the infratemporal fossa was accessed, the foramen ovale and the third
division of the fifth cranial nerve could be identified.
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Figure 1. Model of a skull with arrows pointing
to the 2 sites of incision (one at the lateral rim and one just anterior to
the temporal hairline) for the endoscopic approach to the regions of the infratemporal
fossa and skull base at the level of the foramen ovale.
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Figure 2. An endoscopic optical dissector
in position through one incision (large arrow) and a suction elevator in position
through the other incision (small arrow).
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Figure 3. Endoscopic optical dissector instruments.
The inset shows the spatula and the 30° scope at its distal tip.
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RESULTS
Figure 4 shows the incised
periosteum, and the muscles in the infratemporal fossa are clearly displayed.
By remaining on the face of the skull base and continuing to elevate the periosteum,
the foramen ovale and the third division of the fifth cranial nerve are visualized.
A probe can then be placed that allows for manipulation of the nerves themselves
(Figure 5) or for direct access
to the foramen ovale itself (Figure 6).
After the zygomatic arch is subsequently removed and a craniotomy is perfomed,
the structures identified endoscopically are confirmed to be truly representative.
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Figure 4. Endoscopic view at the level of
the skull base just medial to the zygomatic arch. The periosteum has been
incised, and the infratemporal fossa musculature is visualized inferiorly;
the foramen ovale is in the distance medially.
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Figure 5. Endoscopic view showing the tip
of a probe adjacent to the fifth cranial nerve.
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Figure 6. Endoscopic view showing the tip
of a probe inserted into the foramen ovale.
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COMMENT
Modern endoscopic equipment has revolutionized many surgical disciplines,
including otolaryngology. Specific to otolaryngology, endoscopes and related
instruments have enabled the development of endoscopic sinus surgery and endoscopic
middle ear otoscopy. The great benefit that using endoscopic equipment provides
is the ability to avoid open surgical maneuvers while still performing safe
and effective investigations or procedures.
Endoscopic access to the infratemporal fossa may provide a unique means
of visualizing and performing minor biopsies in this region. To date, we have
peformed 6 cadaveric and 1 clinical dissection. The patient was a child and
was placed under general anesthesia for the procedure. Certainly for children,
and probably for adults, the procedure requires general anesthesia, because
it includes substantial periosteal elevation. As the technique evolves, it
may be possible to perform the procedure on adults with the use of local anesthesia.
The equipment used for these dissections was designed initially for
brow lifting. As such, the angulations of some of the instruments are not
conducive to this form of surgery. We are presently developing instruments
that are specifically designed to navigate around the angles of the skull
base. To that end, we are also developing insulated instruments that will
allow for electrocautery and may allow for some degree of hemostatic control.
As stated previously, the procedures for which this form of endoscopy
might be warranted include those in which visualization of the fossa would
change management or in which a biopsy might be required. Another possible
use for this surgical technique may be to provide a simple and direct route
to the foramen ovale. Procedures such as percutaneous rhizotomy require access
to the foramen ovale.10-11 With
the percutaneous approach, a small radiation dose in the form of fluoroscopy
is required to demonstrate the position of the needle tip relative to the
foramen; an endoscopic approach might alleviate the need for fluoroscopy and
provide another means of access. Finally, bony deficits, acquired and congenital,
associated with cerebrospinal fluid fistulae may be directly and noninvasively
addressed.
In conclusion, this study represents a small initial investigation concerning
a new surgical endoscopic technique. More work will be required first in the
cadaveric model and then in the clinical realm to define the role of endoscopy
in the surgical armamentarium of the otolaryngologist.
AUTHOR INFORMATION
Accepted for publication June 11, 2001.
Presented at the annual meeting of the American Society for Pediatric
Otolaryngology, Scottsdale, Ariz, May 11, 2001.
Corresponding author: Christopher J. Hartnick, MD, Department of
Otolaryngology, Massachusetts Eye and Ear Infirmary, 243 Charles St, Boston,
MA 02114 (e-mail: christopher_hartnick{at}meei.harvard.edu).
From the Departments of Pediatric Otolaryngology (Drs Hartnick and
Myer) and Pediatric Neurosurgery (Dr Myseros), Children's Hospital Medical
Center, Cincinnati, Ohio. Dr Hartnick is now with the Department of Otolaryngology,
Massachusetts Eye and Ear Infirmary, Boston.
REFERENCES
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