 |
|
 |
 |
| |
News -> November, 1999 News
The sphenoid sinus has only recently been targeted by a few authors reviewing
pathology and surgical approaches. In many respects it is the 'forgotten'
sinus with most attention given to the other more commonly involved sinuses.
However, because of the fact that the sphenoid sinus sits in the skull base
with important neurological and vascular structures around it and in it, it
is important when disease or complications of disease warrant surgery that
surgical approaches are clear. Disease in the sphenoid sinus should be
approached with caution. When patients fail medical therapy, there is a
suspicion of tumor, or a complicated sinusitis, surgery is recommended.
The following surgical approaches to the sphenoid sinus have been described:
Via Maxillary Sinus
This is a standard approach which can be initially approached using a
Caldwell Luc, Denker procedure (Weber Ferguson), or a facial degloving.
Once in the maxillary sinus, a large middle meatal antrostomy is made
and the anterior wall of the sphenoid approached through the antrostomy
side by following the medial maxillary sinus wall and proceeding through
the basal lamella. Another approach is through the medial aspect of the
posterior portion of the root of the maxillary sinus (above the internal
maxillary artery), thereby entering into the posterior ethmoid sinus.
Through this sinus, the sphenoid sinus is entered. It is important to note
that at the point of the initial Caldwell Luc opening the anterior sphenoid
wall is only 4-5 cm away (not the 7 cm from the intranasal approach). Thus,
skull base, carotid, and optic nerve can be easily injured.
Transnasal Approaches Without the Endoscope
In order to visualize the anterior sphenoid wall well, the middle turbinate
requires removal. The vessels beneath the sphenoid are avoided. The sphenoid
is measured and 1- 1 1/2 cm above the choana, the sphenoid is entered and the
disease is dealt with.
Endoscopic Sphenoid Approaches Medial to the Middle Turbinate
Using a 0o endoscope the middle turbinate is gently pushed laterally.
The superior turbinate is noted along with the choana. Medial to the lower
1/3 of the superior turbinate (about 1- 1 1/2 cms above the choana) a probe
is placed at the sphenoid ostium which should measure 7 cms in the average
adult. Measurement of the distance to the choana will give an exact measurement
of the distance to the anterior wall. The lower 1/3 of the superior turbinate
is removed and the sphenoid sinus can be opened medial to the attachment of
the superior turbinate and widened laterally. Disease is biopsied, removed,
or drained as necessary.
Endoscopic Sphenoid Approaches Lateral to Middle Turbinate
Ethmoidectomy is performed to the basal lamella. The basal lamella is
measured (usually at 6 cm in the adult) and opened. Medially, the drainage
opening from the posterior ethmoid is located and the superior turbinate
identified. A plane parallel to the lower part of the middle turbinate and
the maxillary antrostomy sets the approach angle to the sphenoid. The lower
1/3 of the superior turbinate is removed and the sphenoid ostium measured
and entered. The sinus anterior wall is opened laterally, as needed. The
first description of entering the sphenoid lateral to the middle turbinate
required direct entry into the sphenoid keeping in a plane parallel to the
lower part of middle turbinate and upper maxillary antrostomy. The basal
lamella is entered and the anterior sphenoid wall measured again at 7 cm.
The sphenoid anterior wall should be convex toward the operator. Anything
concave is anterior skull base. Parsons described moving medially along
the anterior sphenoid wall and running into the superior turbinate. At
this point the vertical 'ridge' is felt andthe natural ostium can be found.
The lateral approach in most experienced hands today requires finding the
natural ostium before the sphenoid is opened.
Middle Turbinate Removal
The lower part of the middle turbinate can be removed to gain wide exposure
to the sphenoid where maximum exposure is needed. Incision into the turbinate
with scissor or punches are made anterior superiorly and posterior inferiorly.
The sphenoid is opened medially as discussed and enlarged as necessary.
Transseptal and Transseptal Endoscopic
The transseptal approach to the sphenoid has been well documented for pituitary
surgery. The sphenoid is entered via the rostrum (bone between two ostia) and
the septal flaps are kept intact. This is usually performed using the microscope.
Another approach is to enter the septum posteriorly at the bony cartilaginous
junction under endoscopic guidance. Flaps are elevated and septal bone is
taken down to the rostrum. The sphenoid can be entered as for pituitary
surgery. While this allows for endoscopic sphenoid surgery, it may be problematic
for the microscope. For large exposure (massive fungal balls or tumor), the
sphenoid using the above described techniques can be opened from orbital wall
to orbital wall across midline, if necessary. Sphenoid disease should be very
carefully removed to avoid injury to the optic nerve (superiorly) and carotid
(posterior laterally). Bleeding can occur from the superior, inferior, and
laterally sphenoid margins and can be controlled with cautery. Of course,
computerized endoscopic sinus surgery is most helpful, if available, to assist
in sphenoid surgery.
Conclusion
Hopefully, this short review will remind surgeons about approaches to the
sphenoid. Safety is paramount and surgically finding the ostium the best
approach. Computerized guidance can be most helpful, especially, for difficult
or extensive disease.
James Chow,
M.D.AAO-HNS Rhinology and Paranasal Sinus Chairman |
James A. Stankiewicz,
M.D. ARS Education Committee Chairman |
|
|
|
|
|
