F OR several years we have used a linear. Limited exposure in cerebral surgery. Technical note. trephine aid drill. Technique

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1 Technical note DONALD H. WILSON, M.D. Section o/ Neurosurgery, Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire ~' A limited exposure is possible, and perhaps preferable, for most cerebral surgery. For some years we have performed all craniotomies with a 2-in. trephine, through a linear incision. The exposure is simple, swift and bloodless. It preserves the integrity of normal tissue as much as possible. Thus, healing is rapid and brain edema is minimal. The technique allows the surgeon to spend most of his time at the target, a particular advantage in microsurgery. KEY WOADS neurosurgical technique cerebral exposure craniotomy trephine aid drill "I believe that the tendency will always be in the direction of exercising greater care and refinement in operating...- WILLIAM HALSTED F OR several years we have used a linear incision and a trephine, 2 in. in diameter, for all supratentorial cranial surgery, except that in the anterior temporal area. Here we have used a craniectomy of the same size. We believe that this method of limited exposure has advantages that are in keeping with the principles of good surgery and with advances in medical technology. Technique All the incisions we use for exposing various parts of the brain are linear, 8 cm in length (Fig. ). For Incisions 2, 4, and 5, the patient is sitting, wrapped in a "g-suit," flexed at the thighs, with his knees at heart level. There have been no instances of air embolus. We have been particularly pleased with the results of surgery on temporal lobe gliomas and middle fossa meningiomas, per- formed through a "tic" exposure in the sitting position. Incision 2 may be angled forward or backward as required. We have encountered one aneurysm of the basilar artery; for this the forward angulation of Incision 2 was used, which was sufficient to clip the aneurysm successfully with the aid of the operating microscope. For parasagittal craniotomy, Incision 6 is used. The head may be flexed or extended as required; for anterior parasagittal craniotomy, it is extended, for posterior surgery, flexed. The patient is semi-sitting with the head higher than the heart. The ~urgeon, directly behind the head, looks down the falx to the corpus callosum. A typical example of the limited exposure method is a frontal craniotomy through Incision. The patient is supine, under endotracheal anesthesia, with the head of the table elevated 5% The patient's head is extended and fixed in a skeletal clamp (Fig. 2). The forehead is cleansed with Ioprep and alcohol. Very little of the well-shampooed hair is removed. An 8-cm line is marked off within a "frown" crease. Adhe- ]02 J. Neurosurg. / Volume 34 / January, 97

2 FIG.. Incisions used for exposing various areas of cerebrum. Fro. 2. Incisions for frontal and parasagittal exposure, surgeon's view. Note medial edge of trephine on sagittal sinus. sive plastic drape covers the skin. The scalp is infiltrated with 0 ml of a standard solution of % xylocaine and /200,000 epinephrine. A short, No. 25 needle is used both intradermally and under the galea. The scalp is incised down to bone and the edges are separated by curved self-retaining retractors. No hemostats or clips are needed on the wound edges. The adrenalin solution, occasional light cautery, and retractors stop all bleeding. A D'Errico trephine, 2 in. in diameter, is then fitted to the Hall Neurairtome* by means of a Hudson drill adapter, which is a standard fitting (Fig. 3). A removable twist drill is inserted into the center of the trephine. This catches the bone first and anchors the trephine until its teeth form a groove. The trephine should be driven slowly at first, by turning the nitrogen pressure * As suggested by scrub technician Rodney Loisell. J. Neurosurg. / Volume 34 / January, 97 03

3 Donald H. Wilson 4 right). With reasonable care the dura will not be nicked. The brain has not been lacerated in any operation. At the end of surgery, the bone disc is replaced and fixed by two No. 32 stainless steel wires. Appropriate holes are drilled in the bone at the time of disc removal. The scalp is closed in two layers with silk sutures. The skin sutures are not cut but serve to secure a stent over the wound (Fig. 5). A stockinette cap completes the dressing. Sutures are removed in 5 days, and the final cosmetic result is pleasing (Fig. 6). Fro. 3. Perforator in D'Errico trephine. down to 70 ppsi or by barely depressing the accelerator (Fig. 4 left). It will then make a clean narrow groove in the bone without jumping or snapping off the twist drill. When a shallow groove is made, the drill is removed. With the trephine guard at its lowest level, drilling is continued at a moderate speed. The guard is raised a few millimeters at a time until the inner table of bone is thin enough to be depressed by a septal elevator or dissector. The disc can then be snapped out by using a periosteal elevator as a lever (Fig. Discussion Most surgeons occasionally use short linear incisions and large trephine openings for selected exposures. We have merely utilized and improved this well-established method so that it is the procedure which in our hands now provides the preferred exposure for practically all situations requiring cerebral surgery. We began to modify our hitherto standard exposures in 966, as a response to the requirements of microsurgery. The microscope allowed us to see well and to work well in small, deep spaces. But the operations were tiring and time-consuming. A swift, simple method of opening and closing seemed to have obvious advantages, which were con- Fro. 4. Left: Air-driven trephine removing bone through linear incision, 8 cm in length. Right: Bone disc removed. Note absence of bleeding from scalp, bone, and epidural space. The ledge on the bone disc was produced by cracking rather than complete penetration by trephine. 04 J. Neurosurg. / Volume 34 / January, 97

4 FIG. 5. Stent closure. Le/t: Skin sutures are not cut, but used to tie over dressing. Right: Stent in place. firmed as our experience grew. We gradually increased its use to include operations where the microscope was not needed. Table lists the variety of conditions we have treated by this method. They seem to Fro. 6. Healed incision 2 days after clipping internal carotid aneurysm. Note small area of hair removed. be representative of the diseases met with in the course of a busy, general neurosurgical practice. The exposures were not enlarged or modified. For instance, all aneurysms on the internal carotid, anterior communicating, and middle cerebral arteries were treated through the single, subfrontal exposure which we have described in detail. The medial edge of the opening is on the sagittal sinus, and the inferior edge on the floor of the frontal sinus. This is comparable to Ray's exposure for hypophysectomy: We believe that a limited exposure, using a linear incision and 2-in. trephine, has many advantages. It is swift and s!mple, allowing more time to be spent at the target. The blood supply to the scalp cannot be compromised by a linear incision. Bleeding from scalp, skull, and epidural space is minimal for the following reasons. The scalp incision is short, infiltrated with adrenalin, and quickly spread; the speed of the trephine produces a thin, dry groove; and, since the bone is removed from outside inward, the dura remains attached to bone at the wound edges. Only a small area of brain is exposed to outside heat and drying, thereby reducing postoperative swelling. Women, especially, are grateful for their retained hair. The ]. Ne:lrosurg. / Volume 34 / January, 97 ]05

5 Donald H. Wilson TABLE Surgical experience with a small cranial exposure (06 craniotomies with trephine and 34 temporal craniectomies, ) Number of Conditions Treated Abscess Aneurysm internal carotid anterior communicating middle cerebral basilar A-V malformation Dementia (brain biopsy) Carotid-cavernous fistula Intractable pain (cingulectomy) Spontaneous hematoma Carcinoma of breast (hypophysectomy) Exophthalmos (orbital unroofing) Rhinorrhea Trigeminal neuralgia Tumor (intrinsic) Tumor (extrinsic)~ Type of Linear Incision (See Fig. ) * Patient was in the supine position. t Section of the portio major in the posterior fossa was done by P. J. Jannetta's method. See ref. 2. Extrinsic tumors included meningiomas, extrasellar and suprasellar tumors. dressing, a stent, is light, comfortable, and as fully protective as a standard bulky dressing. Also, it stays in place. Infection and wound disruptions have been rare and uncomplicated. On two occasions an unnoticed nick was made in the frontal sinus. Infection occurred, the bone discs were removed, and the sinus was closed with a periosteal flap. Later, an acrylic cranioplasty was performed. The reopened wounds still closed to a hairline. The ideal exposure is one which is large enough to do the job well, while preserving the integrity of as much normal tissue as possible. We make no fetish of keyhole surgery. A large arteriovenous malformation, hemispherectomy, and some epilepsy surgery would certainly require large standard craniotomies. However, we believe, with Scoville and Ore, 4 that a limited exposure is possible and perhaps preferable for most cerebral surgery. References. Halsted WS: Surgical Papers, vol. Baltimore, Johns Hopkins Press, 924, p Jannetta PJ, Rand RW" Transtentorial retrogasserian rhizotomy in trigeminal neuralgia by microneurosurgical technique. Bull Los Angeles Neurol Soe 3:93-99, Ray B: Intracranial hypophyseetomy. $ Neurosurg 28:80-86, Scoville WB, Ore GD: Large trephine craniotoroles. Acta Neurol Lat Amer 6: , 960 Received for publication November 7, 969. Address reprint requests to: Donald H. Wilson, M.D., Hitchcock Clinic, Hanover, New Hampshire Neurosurg. / Volume 34 / January, 97