Decompressive Craniectomy
Intervention for traumatic brain injury.
A decompressive craniectomy addresses traumatic brain injuries where swelling is involved. This procedure involves the removal of a portion of the bony cranium and the creating an opening in the dura in order to alleviate pressure from swelling.
Positioning
The patient is positioned supine, with the head rotated laterally as close to 90 degrees as possible with a shoulder support. The head is tilted slightly posteriorly. A Mayfield Skull Clamp is used to secure the skull in 3 places. Alternatively, a foam donut or a twisted surgical drape coiled in the shape of a head ring may be used to secure the head.
Incision Planning
A mark is made across the sagittal crest to denote the superior sagittal sinus, which should be avoided at all costs.
A mark is made at the root of the zygomatic arch, one fingerbreadth anterior to the tragus. Extend the mark superiorly, extending above and around the pinna over the parietal bone. Extend towards the inion and curve towards the midline, staying at least one finger distance from the midline sagittal sinus marker. End the mark anteriorly near the hairline. The final planned incision should be a reverse question mark shape.
Exposing the Surgical Site
The incision is opening in 3 portions. The first two, most anterior portions are opened (A. and B.), with the incision moving through the galea but leaving the periosteum intact. Bleeding of the area is stabilized before moving forward.
The third portion (C.) is opened, leaving the temporalis mm. intact. After the entire skin incision has been made, it can be reflected from posterior to anterior.
To keep the surgical field clear, a few sutures can be placed along the tethered edge of the skin flap. A 4x4 gauze may be rolled and placed under the skin flap to preserve blood supply to the flap.
Pericranium Harvesting
A portion of pericranium is freed from the bone and temporalis mm.–but kept attached at its most anterior point to ensure vascularization. Pericranium may be freed as far as the boarder of the surgical field.
Alternatively, a large portion of pericranium may be harvest and placed in sterile saline until needed later.
Temporalis mm. Reflection
Return to the temporalis mm. and scrape the fibers perpendicularly to the direction they travel, clearing the temporal line. Reflect the muscle out of the surgical field.
Burr Hole Creation
To assist with lifting the bony flap, burr holes are created using a Hudson brace. Starting at the root of the zygoma, a burr hole is planned for every 4-5 cm following the border of the incision (about a fingersbredth internal to the incision).
Burr holes should be close enough to not lose sight of Gigli saw or guide and far enough to not require excess burr holes during the next steps.
Removal of Cranial Bone
Starting at the first burr hole, the Gigli saw guide and Gigi saw are passed underneath the cranium and above the dura to each adjacent burr hole. Once pulled though, artery forceps (hemostats) are clamped on each end of the Gigli saw. These forceps serve as handles. Each end of the Gigli saw is pulled through the holes in a see-saw motion, applying pulling force to create an incision through the bone from deep to superficial.
The saw is passed between each of the burr holes until a complete incision has been made.
Cranial Bone Removal Safeguard
When lifting the excised portion of the bony cranium, it may be useful to apply counter-pressure using a Penfield 2 or 3 (McDonald). One tool is positioned anteriorly in order to avoid pushing the cranium into the brain during elevation. The other tool begins posteriorly and frees the cranium from the dura.
Additional Bony Removal
A double action rongeur may be used to chip off additional portions of the bone closer to the zygoma.
It is important to make sure that the dura is can be opened near the temporal lobe to allow for lateral swelling in order to avoid medial swelling (uncal herniation) into the brainstem.
Hemostasis
With the portion of cranium removed, bone wax may be used to stop bleeding from the bone edge.
Dural Tenting
Prior to opening the dura, dural tenting should be performed to avoid excess accumulation of blood. A suture is thrown shallowly through the dura and either fed through the remaining bony cranium or through the adjacent pericranium. The slight raising of the dura edges ensures that blood does not pool in the epidural space.
Durotomy
With the dura exposed, a cruciate or C-shaped incision is made to allow for relief of pressure from brain swelling.
Dural Closure
With the leaflets from the cruciate incision replaced, the edges may not meet cleanly if there is residual swelling of the brain.
The portion of harvested pericranium may be sewn into the dura in order to create a seal for CSF while still accommodating the increased brain swelling.
Surgical Area Closure
Once it is confirmed that there is no leaking of CSF, the area can be closed by first replacing the temporalis mm. and adding a few sutures to keep it in place over the dura. The galea and skin can be closed.
A drain tube is placed posterior to the surgical incision. The drain is removed 2-5 days postoperatively to avoid tampering with the healing.
Additional Note
If there is a need for a cranioplasty to be performed in the future, the removed piece of cranium may be stored in the patient's abdomen. This offers an optimal environment for the portion of bone to receive blood prior to replacement.
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