Indications

E.g. for sphenoorbital meningiomas

Monitoring

SSEPs only

Medications

Mannitol 0.5 g/kg, Keppra 1000 mg, dexamethasone 10 mg

Pinning

Mastoid-to-mastoid, like for an EEA. Single pin on the right mastoid. Lower double pin on the left mastoid. Upper double pin canted slightly forward, on the superior temporal line. 

Positioning

The bed is turned 90 degrees with the side of the pathology away from anesthesia. 

Supine, no bump. Make sure the side of the patient is flush with the side of the bed of that the operator is on. 

Regular Mayfield, no need for the 360. 

Positioning the head: 

• Extend the neck
• Rotate the head about 20 degrees away from the operator

Mapping

Map out the location of the frontalis branches of the facial nerve using a non-sterile Kartush stimulator. This defines the furthest limit of your incision. 

You are looking for muscle twitches in the frontalis muscle. The orbicularis oculi will also twitch but this is not your end point. 

Map the path of the frontalis branches and mark with a marking pen. 

Marking

Mark an incision extending laterally from the lateral canthus to about 1.5 cm. The furthest lateral extent of your incision is defined by the path of the frontalis branches of the facial nerve mapped out in the above step. 

Alternatively, you can consider an eyelid incision as marked below. This is useful if you need to include an anterior clinoidectomy because it allows you to approach the clinoid from the top as well as from the side. 

Prep

Use ophthalmic Betadine to prep the skin and sclera of the eye. 

Use lidocaine with epinephrine to locally anesthetize the planned incision. 

Protect the cornea with a corneal shield which is sutured at its medial edge to the upper and lower lids with 6-0 Prolene. 

Approach

Use a 15 blade to make a lateral canthotomy, cutting down to the bone. Follow this with a lateral cantholysis, severing the superior and inferior lateral canthal tendons. This will bring you to the orbital rim. 

Your assistant will retract the edges of the skin with small sharp rake retractors. 

Use a Bovie with a Colorado tip set to 15 and 15 to incise the periosteum down to the bone in a T shape as below. 

Use a Penfield 1 periosteal elevator to elevate the periosteum from the lateral orbital rim. Go up and down the zygoma as far as the incision allows. Also dissect periosteum from the inside of the orbit. Follow the plane laterally and separate the temporalis muscle from the posterior edge of the orbital rim. 

If you encounter the zygomaticofacial nerve (a sensory nerve), cauterize it with a bipolar and cut it. 

Orbitotomy

Use the B1 drill bit without the foot plate to make these bony cuts.

The inferior chevron-shaped cut begins at the inferior orbital fissure medially. 

Use a brain ribbon to protect the orbital contents while the osteotomies are being made. 

The final cut (yellow line below) is made from within the orbit and connects the two prior cuts. Be sure to protect the orbital contents with a brain ribbon. 

This does not have to go completely through the bone. It is enough to score it and use a rongeur to fracture it. 

Craniectomy

Once the orbital rim is removed, you can begin work on the craniotomy. 

Dissect the temporalis muscle away from the temporal fossa using a Bovie. Be sure to stay sub-periosteal. 

Take the muscular dissection as far superiorly as the superior temporal line. Indeed, you should come across the superior temporal line to free the temporalis muscle and allow it to be retracted laterally. 

Use an M8 drill bit to perform the craniectomy. Expose the frontal and temporal dura before working on the sphenoid wing. 

In this picture, the craniotomy is shown in red and the underlying location of the sphenoid wing in black. 

This part is important: thin the bone of the remaining part of the lateral orbital wall but do not expose periorbita yet. The periorbita may be exposed later, but reserve this for the end of the case to avoid having periorbita herniating into your field the whole case. 

Use image guidance to verify that you have achieved margins surrounding the whole tumor before making dural incision. 

Use the titanium spring scissors to cut a circle around the tumor then peel it away from the brain. 

The dura of the temporal lobe is tightly attached to the lateral cavernous sinus and must be sharply dissected with a 15 blade at three points:

1. Superior orbital fissure
2. Foramen rotundum
3. Foramen ovale

Closure

Lay a large piece of Alloderm onlay over the exposed brain. 

Harvest a large fat graft "enough to fill a shot glass." Use this to fill the defect in the temporal bone. We are no longer using cement cranioplasties. The bone is left open. 

 Plate the bone as below:

When attaching the bone, place a finger against the edge of the bone to ensure that the edges of the orbital rim are realigning correctly. 

Use a Biodesign porcine repair graft to repair the periorbita. Start by tacking the the graft to the deep edge of periorbita using 3-0 Polysorb suture followed by securing the superficial edge to the periorbita in the same manner. Use simple interrupted sutures. 

Reattach the temporalis to the lateral orbital rim using 3-0 Polysorb suture. The superior border of the temporalis is not reapproximated to the superior temporal line. 

For closure of the skin incision, begin by reapproximating the edges of the lateral canthus using a single simple interrupted inverted 3-0 Polysorb suture. 

Close the dermal layer of the skin incision using simple interrupted inverted 3-0 Polysorb sutures. 

Close the skin with a running horizontal mattress 6-0 Prolene suture. Take small bites (i.e. near the edge of the skin). 

Dress with Xeroform dressing on the incision followed by an eye patch secured with paper tape. 

Remove the stitches after 7 days. 

Orders

SBP cap 150, dexamethasone 4 mg q6, Keppra 500 BID, CT head. 

Place a lumbar drain

Video