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Supraorbital Craniotomy for Intraorbital Tumors

December 17, 2015

Transcript

This procedure reviews the tenants for a supraorbital craniotomy via an eyebrow incision for resection of intraorbital tumors. This is a young patient who presented with proptosis and slight decrease in vision in the left eye. And on MRI evaluation was noted to have a slightly heterogeneously enhancing mass in their superior comportment of the orbit placing some mass effect on the levator muscle. This lesion was hyperintense on T2 and caused some erosion of the bone in the superior part of the orbit. This tumor was suspected to be a schwannoma or another benign lesion within the orbit. Let's review their nuances for performance of an eyebrow incision. The head of the patient is placed in a skull clamp. The incision is just above the eyebrow. I avoid placing the incision within the eyebrow, as this can increase the risk of alopecia. The incision is also curved slightly posteriorly to enhance the exposure within the keyhole. The super orbital framing and nerve are also marked, so then the incision can only slightly extend medial to the nerve. Another view of their head positioning is also included to better demonstrate the slight curve more posteriorly to enhance the exposure within the key hole. This extension incision often heals very nicely and is not associated with any evidence of cosmetic deformity. A lumbar drain is also placed at the beginning of the procedure to enhance dural decompression during osteotomy, the incision is completed all the way to the level of the pericranium. Monopolar cautery is used to reflect the pericranium anteriorly. The super orbital nerve is identified along the medial edge of the incision and is released within this subcutaneous space. Here's the pericranium being reflected around the rim of the orbit as the pericranium joins that pre-orbita in this region. Here is the pre-orbita. Next, the periorbita is generously dissected from the roof of the orbit. The dissection of the bone is continued over the frontal processes of zygoma. As much of the bone laterally is exposed as possible here as further extension of the pericranium anteriorly and reflection of the periorbital away from the inner aspect of the orbital roof. Here is the super orbital nerve that is also released from its foramen and carefully protected so it can be slightly mobilized more medially. Here you can see the groove of the super orbital nerve. Sometimes there is a foramen there and the nerve is obviously confined within the foramen and cannot be effectively mobilized. As much of the pericranium from the calvarium is mobilized and next the fat pad, along with the temporalis muscles reflected posteriorly. Again, the fat pad is not transected across its length to prevent injury to the frontalis nerve but rather the fat pad and the temporalis muscle are reflected more posteriorly. Release incisions can be made within the pericranium parallel to the supraorbital nerve to maximize the exposure of the funnel bone. Here is additional extension of the muscle removal over the frontal process of zygoma. Every millimeter matters in an eyebrow incision to extend the exposure. The upper hole is placed within the key hole area and the orbital contents are protected via spatula. Kerrison rongeurs expand the exposure over the frontal dura and the osteotomy is performed using a B1 bit without a footplate. This exposure is relatively limited in this patient, despite my significant efforts to provide mobilization of the muscle and pericranium. And therefore at B1 without a footplate was used to conduct a first osteotomy across the frontal process of zygoma. Next, just medial to the foramen of the super orbital nerve, the second osteotomy is completed to complete the craniotomy over the funnel area. Next I mobilize the frontal bone by fracturing its attachment across the orbital roof. The bone over that area is somewhat thinned out by the tumor, and so mobilization of this part of the bone is relatively easy. The frontal sinus was entered in this patient, so the mucosa was thoroughly obliterated using pituitary rongeurs and a piece of temporalis muscle was used to plug the sinus in order to minimize the risk of post-operative CSF leakage. At this juncture, I proceed to remove part of the bone along the orbital roof in order to again, expand my operative trajectory across the sub frontal area if the goal is to proceed with an intradermal procedure. In this case, we dive our attention to the orbit where the interorbital tumor is the surgical target. The pre-orbital is incised. You can see the tumor is very well dileniated and has incorporated one of the nerves over the levator, so this is most likely a schwannoma. You can see the distal end of the nerve. Next I use Q-tips to mobilize the soft tissues and the pre orbital fat away from the tumor. And then I'll go ahead and find the proximal and distal ends of the nerve that is affected by this schwannoma and cut those nerves and deliver the tumor. At this step, the incision within the periorbital is extended more posteriorly and the inferior pole of the tumor is dissected and released from the interorbital contents. The Q-tip can be quite effective, not as a microsurgical instrument, but as a more effective instrument to mobilize the orbital fat away without placing the fat at risk of being moved into the suction device. Here is the distal end of the nerve that is coagulated and cut. Now I move the tumor more superiorly and try to find other attachments to the surrounding structures along the tumor capsule. Here's the more distal end of the nerve that is affected by the tumor or in reality, the more proximal part of the nerve that is affected by the tumor. This end was also coagulated and cut, and the tumor was removed in block. Further inspection reveals no residual tumor within the resection cavity and very satisfied with the extent of resection. The frontal sinus that was initially entered is revisited and a piece of bone wax mixed with bacitracin powder is used to plug this opening further. The bone flap is replaced using mini plates, paying special attention to ensure adequate reconstruction of the alignment of the orbital rim, as you can see here. I'll make sure the edge of the bone across the rim on both sides are lined up adequately. The same for the area of the frontal process of zygoma. After the plating is complete, cranioplasty is performed to fill the boning defects and avoid any delayed cosmetic deformity from sinking of the scalp. Here's the result of the cranioplasty. Next, the scalp is closed in the anatomical layers using 3-0 absorbable sutures in the pericranium. Other sutures are used to further close the next layer, which is the subcutaneous space and 4-0 nylon sutures are used to close the skin. These sutures are removed about three to five days after surgery for maximal cosmetic outcome.

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