Fig. 8.1 (a,b) Positioning. The head is placed horizontally. The body position is either supine, supine 30°, or lateral. The body and head are elevated approximately 15° to reduce intracranial pressure (ICP) and to facilitate venous return. Care is taken not to angle the head in relation to the body (see straight yellow line in b). In trauma patients, check the cervical spine (C-spine) before positioning. If it is not possible to clear the C-spine, a lateral body position with the neck collar in place is preferred. A horizontal orientation for the Mayfield head holder gives the surgeon more space. Pins, placed at a distance from the skin incision, facilitate skin closure. A Leyla bar on the occipital site enables placement of skin/fish hooks for retraction of the myocutaneous flap.Fig. 8.2 (a,b) Anatomy overview. Landmarks are (1) the tragus for the lower limit of skin incision, (2) zygomatic process of the frontal bone for the anterior cranial base, (3) opisthocranion as the most posterior part of the skull for the posterior inferior limit of skin incision, and (4) the midline. A landmark for the transverse sinus and the torcular is the line drawn from the epicanthus lateralis to the point where the ear (helix) connects to the scalp. The extension of this line approximates the position of the transverse sinus and the torcular/inion.Fig. 8.3 (a,b) Shaving and draping. Simply shave a strip (as broad as the width of the clipper) or the hemicranium.Fig. 8.4 (a,b) Skin incision. The question-mark-like skin incision follows the four landmarks mentioned above. Because a common mistake is to perform a craniectomy that is too small to allow extension of the brain without shearing at the bone edges, the skin incision should be large enough to perform a temporal decompression and follow more or less the transverse and sagittal sinus. Avoiding a sharp angle behind the ear leads to less scalp necrosis and better wound healing.Fig. 8.5 (a,b) Contralateral midline crossing. The cross-midline skin incision is used to facilitate reinsertion of the bone flap. The craniectomy should extend close (~1.5 cm) to the midline. The skin incision should be made outside the craniectomy line. It simplifies the surgical procedure of reinsertion of the bone flap, because it allows to cut the skin down through the scar straight to the level of the bone. By contrast, if the scar lies over the craniectomy, i.e., over brain tissue, it takes much longer to find and dissect the desired layer, and complications are more likely. Therefore, the cross-midline skin incision is recommended to facilitate reinsertion of the bone flap.Fig. 8.6 (a,b) Alternative skin incision. A T-shaped skin incision is an alternative to a hockey stick (a). However, it may somewhat increase wound healing complications compared to the question mark incision because it requires cutting two 90° angles. Sometimes a decompressive hemicraniectomy has to be performed secondarily after a smaller craniotomy, for example, after aneurysm clipping or the removal of a subdural hematoma (b). In these cases, a skin incision already exists and can be extended. Then, a more or less T-shaped skin incision can be performed allowing exposure of the hemicranium while still enabling good wound healing (b). This approach faces the same problem of two 90° cuts. Coagulation in this area (circle) should be avoided and the skin suture at these edges should be tightened only gently to maintain blood supply.Fig. 8.7 (a,b) Myocutaneous flap and muscle handling. The skin is incised down to the level of the bone. Skin clips are placed to control bleeding. The main trunk of the superficial temporal artery (see Chapter 5.2.2) and the parietal branch should be saved. The skin flap is elevated from frontal and parietal toward the temporal muscle which is still fixed to the bone and the galea. Upon reaching the edge of the muscle, it is sharply incised and detached from the temporal bone, but left completely attached to the skin and galea flap.Fig. 8.8 (a,b) Exposure of the hemicranium. Then the single myocutaneous flap is developed toward the frontal and temporal base. Fish hooks are used to retract the flap.Fig. 8.9 (a,b) Burr holes and craniotomy. Placing the burr holes should not follow any dogma. The goal is to saw the bone flap quickly and easily without damaging the dura or the sinuses. One practical routine is the following four-burr hole technique: (1) one at the temporal base, root of zygoma, (2) one at the bregma, approximately 1.5–2 cm from the midline (use the width of the burr: one width from midline), (3) one just behind the lambdoid suture, (4) one between the bregma and the lambdoid hole, next to the midline (one burr-width away from the midline).There is a reason for the location of every burr hole: (1) to mark the level of the skull base at the middle fossa—remember to decompress osteoclastic down to the level of the middle fossa and not to leave any form of balcony that is sufficient for the temporal bone to serve as a support for herniation into the temporal notch: (2) safe mark for midline and cosmesis—the burr hole is usually way behind the hairline: (3) makes sure that the bone flap is wide enough: (4) enables straightforward sawing down along the superior sagittal sinus (SSS) without running into the SSS (just make a line between burr holes 2 and 4).Cave: remember the basal temporal bone is sometimes very pneumatized with a high risk of rhinoliquorrea after decompressive craniectomy. Seal air cells (e.g., with bone wax, muscle, or glue).Fig. 8.10 (a,b) Lifting the bone flap. It is usually difficult to lift the bone flap. It is tightly fixed by the dura and lifting one edge to allow better access to the inner table to detach the dura often pushes the other side into the brain. Sometimes several elevators have to be used to prevent this. One or more additional burr holes (x) may help in detaching the dura.Fig. 8.11 (a–d) Dural opening. Open the dura in a C-shaped fashion around the sylvian fissure and then release the dura in stellate fashion up to the bony edges (stellate: because of the bridging veins; be careful not to cut these veins that run, often attached to the dura, close to the sinuses). Cover brain with Tabotamb or any other (reasonably priced and rapidly available) material. The goal is to promote the formation of a neo-dura that covers the brain and provides a readily available plane for dissection at the time of reinsertion of the bone. There is no need to add any form of dura plastic.1Fig. 8.12 (a–d) Decompressive hemicraniectomy to treat increased ICP. Decompressive craniectomy in a patient with an ICP probe. (a) The cross midline skin incision, (b) the one-layer myocutaneous flap, and (c) the dural opening. (d) After lifting of the bone flap (hemicraniectomy) ICP drops from around 70 to 25 mm Hg and only after large opening of the dura, the ICP decreases further to around 8 mm Hg.
Skin Closure
Before closure, think about an ICP monitor. An intraparenchymatous ICP probe can facilitate the management of the patient on the ICU.
After covering the brain loosely with dura mater (do not use sutures) and placing a subgaleal drain without active suction, the myocutaneous skin flap is turned back. The galea is sutured subcutaneously, before applying skin staples or running skin suture, or the skin–galea is sutured with large stitches.
In the case of a T-shaped skin incision: do not apply tension to the edges where the T-shaped incision approximates, because this is the most vulnerable site (to avoid necrosis of the skin).
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