Positioning

Patient is positioned supine on a horseshoe with the horseshoe angled so that it is tucked up underneath the occiput and the head is level.  A small bump is positioned transverse across the shoulder blades to elevate the chest.  The left arm is tucked.  The head is shaved.  

Marking

A bicoronal incision is made to start just ahead of the tragus on both sides, arcing up and gently backwards close to the pinna and coursing superiorly and anteriorly towards the crown of the head.  Incisions from both sides meet just anterior to the coronal suture forming a widow's peak with a gentle curve, not a corner.  

Draping

The head is prepped, and the drapes are applied, one running posteriorly from tragus to tragus and hugging the horseshoe, and the other running from tragus to tragus anteriorly along the orbital ridge just showing both eyebrows.  

Local anesthetic with epinephrine is used to infiltrate the incision line after the second prep and a third prep follows.

Exposure

Skin incision is made with a 10 blade just through the galea and no deeper.  A Metzenbaum or curved Mayo scissor is used to cut through the galea taking care as one approaches the tragus to preserve bilateral STA's.  Raney clips are applied along the length of the incision.  

Double skin hooks are used by the assistant to elevate the skin edge while the surgeon uses a Metzenbaum scissor to develop the plane between the galea and pericranium, carrying the dissection closest to the galea.  Alternatively, blunt dissection with fingers and a dry Ray-Tec can be used to develop this plane.  The plane is developed both posteriorly towards the back of the head and anteriorly towards the orbital rims.  Once dissection has been carried to the orbital rim, the exposure is complete.  

The pericranium is supplied by bilateral supraorbital arteries from the front and no vasculature crosses the superior temporal line laterally.  

Pericranial flap

A coronal incision is made in the pericranium down to the bone at the posterior aspect of the exposure, posterior to the skin incision, as far back as possible.  

Incisions are made in the sagittal plane along bilateral superior temporal lines.  

Sharp dissection with a 1 Penfield, Love Adson, or broad periosteal elevator is used to separate the pericranium from the bone, taking care not to create a hole in the pericranium.

Decompression

Depending on the case, there may be extensive fractures of the frontal bone, and a bifrontal decompression may be necessary.  

Bone fragments are elevated, removed, and discarded.  Care is taken around the sagittal suture in case bleeding is encountered from the superior sagittal sinus.

Widen the craniectomy as necessary to adequately decompress the frontal lobes. If necessary, drill down sharp bone edges such that the pericranial flap is not making an acute turn to pass into the skull. Debride necrotic brain with suction as needed.

The pericranial flap is freed from the superior temporal line.

Occasionally, when a larger flap is needed or parts of the pericranium are devascularized due to trauma, the temporalis muscle and deep temporal fascia can be retained and used as part of the flap. 

The flap is  wrapped in wet lap sponges and folded to the side.

Intracranial preparation

The dura is dissected from the inner table of the skull and followed anteriorly along the skull base, the anterior cranial fossa.  

The olfactory fibers are divided, and the dissection carried past the olfactory foramina of the cribriform plate then posteriorly to the planum sphenoidale.  

An M8 drill bit is used to exenterate the frontal sinus.  If fractures have exposed the ethmoid air cells, the mucosa can be cauterized with a Bovie.  

Bilateral frontonasal ducts are plugged with pieces of temporalis muscle.  

Additional pieces of temporalis muscle can be used to plug further bony defects such as in the planum sphenoidale leading to the sphenoid sinus.  

Muscle grafts are covered with a free flap of the deep temporal fascia.  The deep temporal fascia free flap is covered with a dermal matrix graft, such as AlloDerm.

A dural substitute graft, such as DuraGen is used to cover the remnants of the frontal lobes.  

The pericranial graft is then laid between the the DuraGen and AlloDerm.

Closure

A 7 flat JP drain is tunneled beginning 4 to 5 cm posterior to the widow's peak of the skin incision and ending over the temporalis muscle.  

The galea is closed with 2-0 Vicryl's and the skin with staples.