Download Minimally invasive purely endoscopic approach to pterygopalatine

Introduction. Orbital approaches can be very challenging and often require the combined expertise of neurosurgeons, ophthalmologists and ENTs. The main
concerns in orbit surgery are the maintenance of vision and ocular movements and the achievement of an acceptable cosmetic result. Traditionally the orbital
approaches are divided in two major categories: the transorbital, which manifest no orbital walls opening and the extraorbital with orbital walls opening.
Endoscopic approaches to the orbit constitute an important addition to the orbital surgery armamentarium the last 2 decades.
Purpose: In this cadaveric study we aim to present a novel minimally invasive, endoscopic approach to the lateral-inferolateral orbit through an extradural
middle fossa route.
Material-Methods: Eight fresh cadaveric heads (16 sides) were prepared for dissection. Anatomic dissection was performed using rod lens endoscope (Karl
Storz, 0 degrees 18 cm length, 4mm diameter). A classic curvilinear incision was performed. The galea flap was turned anteriorly after performing a subfascial
dissection. The upper edge of the zygomatic arch was exposed and drilled with a diamond burr size 3. After the exposure of the lower lateral middle fossa wall
a 2cm length by 1 cm height craniotomy was performed. With the use of the endoscope the dura matter was dissected from the anterior part of the middle fossa
and the foramen rotundum, was identified. The latera part of the superior orbital fissure was also identified ant the meningo-orbital band was dissected. The
bone covering the foramen rotundum was drilled using a 3 mm cutting drill and the intraforaminal V2 was exposed. By removing more bone and following the
route of V2 the superior aspect of the pterygopalatine fossa was exposed. Further bone removal towards the supraorbital fissure exposes the periorbita at the
lateral wall of the orbit.
Results: The part of the greater sphenoid wing between the supraorbital and infraorbital fissure was removed and the lateral periorbital surface was exposed.
In all the specimens the posterior 2/3 of the lateral orbital wall was removed and the anterior limit of the removal was the sphenozygomatic suture. The inferior
orbital fissure was identified just in front of the pterygopalatine fossa. After removing the fat the infraorbital nerve entering the orbit was exposed. The junction
of the lateral and inferior wall of the orbit had to be drill for the better exposure of the infraorbital nerve. At the floor of the orbit the infraorbital groove/canal
was identified
Figure 3. A. Dissection of the dura matter- meningeal layer from the superior orbital
fissure (SOB) and cutting of the meningo-orbital band (MOB). B. Further “peeling
off’’ the dura reveals the SOF contents and the anterior clinoid process (ACP).
*middle fossa dura, **anterior fossa dura. GWSB: Great Wing- Sphenoid Bone, LWSB:
Lesser Wing- Sphenoid Bone.
Figure 1. A, B. 2x1cm craniotomy was centered above the temporozygomatic suture
of the zygomatic arch and its anterior border about 1 cm posterior to the
sphenozygomatic suture (junction of greater sphenoid wing with the body of the
zygomatic bone). The upper border of the zygomatic arch was drilled out. C. After
stripping the temporalis muscle off the anterior-inferior surface of the temporal fossa
the craniotomy was performed using a high speed 3 mm cutting drill and the side
cutter craniotome. D. The dura matter was elevated from the middle fossa floor using
a Penfield dissector.
Figure 4. A. Extending the bone removal lateral to the superior orbital fissure and
parallel to the lesser sphenoid wing. B. removal of the fascia creating the roof of the
pterygopalatine fossa and infraorbital fissure reveals the V2 nerve, as well the
posterior superior alveolar nerve. The pterygopalatine ganglion located at a lower
level inside the pterygopalatine fossa (not seen in the picture). A connecting branch
between V2 and ganglion can be seen
Figure 2. A. Identification of the foramen rotundum and the V2 nerve after dissecting
the dura matter off the middle fossa floor. Using a diamond 3mm drill enlargement
of the foramen rotundum was achieved. B. Further bone removal following the
route of the V2 nerve drove us to the roof of the pterygopalatine fossa. C. Extending
the removal of the greater sphenoid wing towards the superior orbital fissure exposes
the periorbita. D. The inferior orbital fissure was exposed anteriorly and lateral to the
pterygopalatine fossa.
Figure 5. A. This skull model depicts the lateral orbital wall removal in a view
through the orbit. B. This picture demonstrates the middle fossa lateral wall
craniotomy (**) and the greater sphenoid wing removal from the lateral orbital wall.
The lateral orbital wall removal is extended superiorly to the sphenofrontal suture,
inferiorly limited by the inferior orbital fissure, and medially by the ankle created
from the superior and inferior orbital fissure. The anterior limit of the bone removal
is close to the sphenozygomatic suture.
Conclusion: The minimally invasive purely endoscopic approach to the superior-lateral aspect of the pterygopalatine fossa and lateral orbit through a middle
fossa extradural route is a good alternative approach to the lateral orbit. Further studies and clinical application of this approach is necessary for a better
evaluation of its usefulness.
References
1. Castelnuovo P. Endoscopic endonasal management of orbital pathologies. Neurosurg Clin N Am 26( 2015) 463-472
2. Fukuda H et al. The meningo-orbital band. Microsurgical anatomy and surgical detachment of the membranous structures through frontotemporal craniotomy with removal of the anterior clinoid process. Journal of Neurological surgery-part
B Vol 75 No B2/2014.