Trauma Flap – Part 2
Trauma Flap 12-4: Burr holes and bone flap. Several burr holes (at least three) are made to create a bone flap that is at least 10 cm × 15 cm. Bone flaps smaller than this would not sufficiently decompress the brain and reduce ICP. When possible, a small ruler can be used to measure back from the keyhole to ensure the anteroposterior extent of the bone flap is 15 cm.
Trauma Flap 12-5: Temporal craniectomy. After removal of the bone flap, the remaining temporal bone must be cut with a rongeur down to the floor of the middle cranial fossa to provide maximal decompression of the lateral brainstem. Care should be taken to bite, and not twist or torque, with the rongeur during bone removal low in the middle fossa. Aggressive maneuvers with the rongeur can open or displace skull base fractures and precipitate uncontrolled bleeding.
Trauma Flap 12-6: Dural opening. After achieving hemostasis, there are several choices for the durotomy. Our preferred method is to open the dura slowly with multiple radial incisions (in a stellate fashion) to provide maximal cerebral decompression (A). Associated hematomas can be removed, and hemostasis can be obtained (B). When the dural opening is completed, closure can be undertaken. Although some surgeons perform a duraplasty, we prefer to leave the durotomy open and simply to cover the brain with a dural substitute or similar material to protect the brain surface and reduce adhesions. The leaves of the dura are folded over the dural substitute. Unless there is an urgent need to leave the operating room, drains are placed over the surface of the dural substitute and tunneled externally. The galea should be closed with numerous, closely spaced interrupted 2-0 absorbable braided sutures. The skin is closed with a running 4-0 absorbable monofilament suture. To ensure a watertight closure, the sutures are placed very close together.Tips from the masters
• With the rare exception of bifrontal extraaxial mass lesions, we have found that good ICP control can be obtained with unilateral decompressive surgery, even in cases of bifrontal contusions. Unilateral decompressive surgery on the side of the larger intraparenchymal injury is technically more straightforward than bifrontal decompression, and a larger decompression can be obtained without manipulation or exposure of the sagittal sinus. Unilateral hemicraniectomy also enables a more extensive decompression low in the temporal region compared with a bifrontal proced1ure. In addition, with attention to the size of the frontal sinuses on CT scan, opening into the frontal sinuses can be more easily avoided in a unilateral decompression. Cranioplasty repair of the skull defect after unilateral decompression is simpler and safer, making it preferable.
• It is crucial to avoid the midline when turning the bone flap. It is easy to get off midline in an emergency setting, however, wherein technical maneuvers and details need to be streamlined. It is a good idea to mark the midline rapidly and place the drapes up to midline so that you are always oriented to the midline, especially if the head is not pinned. The location of the sagittal suture can also be used to determine midline.
• Preparing the contralateral Kocher point for invasive neuromonitoring with a ventricular catheter during the head shave can save some time after the case.
• Arterial blood exiting from the middle fossa in large amounts warrants exploration and often arises from the middle meningeal artery or the sphenoid wing. If this bleeding is seen, a slightly more conservative temporal craniectomy provides bone to which the temporal dura can be tacked, which may stop the bleeding.
In experienced hands, wound complications are the most common source of surgical morbidity with this procedure. These complications largely result from either traumatic injury to the skin in the region of the incision or cerebrospinal fluid egress caused by a combination of the widely open dura and the resultant cerebrospinal fluid absorption problems many patients develop. Diligent attention to closure, including multiple, closely spaced inverted galeal stitches; the routine prolonged use of drains; and skin closure with running absorbable monofilament suture have nearly eliminated these problems at our institution.
Leaving at least two Jackson-Pratt drains in the surgical cavity is highly recommended because these patients often do not clot properly, and without the tamponading effect provided by the bone flap, the risk of symptomatic epidural hemorrhage is high.
Although it is tempting to rush the dural opening, given the urgency of these cases, we recommend a slower dural opening because we have seen sudden cardiovascular collapse and profound hypotension resulting from sudden reversal of elevated ICP and the loss of the catecholamine support that comes with the Cushing response. Adequate resuscitation by anesthesia can also prevent this complication. In most cases, a central line can facilitate a successful resuscitation.
The dura over the anterior frontal lobe is commonly torn, typically in emergencies and older patients. It is a good practice to assume that the dura may be incompetent in the frontal area and to begin to strip the dura and elevate the bone flap away from this site.
A skull fracture contralateral to the side of decompression is a significant risk factor for a postoperative epidural hematoma. A routine CT scan early after decompressive hemicraniectomy should be considered in patients who harbor a skull fracture remote to the site of decompression. Precipitous external herniation can rarely occur intraoperatively, soon after decompression. Especially in the setting of a contralateral skull fracture, empiric surgical exploration on the other side, without an interim CT scan, may be considered.Bailout options
• Uncontrolled external cerebral herniation after decompression can make primary closure of the scalp difficult. If this possibility is suspected in advance, it is wise to obtain hemostasis and be prepared to close before the dura is opened.
• In especially urgent cases, such as cases with recent development of anisocoria and an underlying subdural hematoma, making a cruciate opening in the dura through the first burr hole may provide some relief of intracranial hypertension during the craniotomy.