S Incision: A Novel Incision for Far Lateral Approaches

Background The far lateral approach is one of the most invasive to the lateral skull base with different incisions described to achieve the necessary exposure, such as a large C incision around the pinna and the hockey-stick incision. Besides adequate exposure, the incision should allow adequate skin closure, minimal postoperative muscle atrophy and pain, and an aesthetically subtle outcome. Despite this, problems such as cerebrospinal fluid (CSF) leaks, muscle atrophy and pain, alopecia, and inadequate intraoperative exposure due to bulging muscle groups are frequent.

With this in mind, we have started successfully using a horizontal (laying down) S incision and aim to describe the technique and surgical series to date.

Surgical Technique The landmarks observed to mark the skin incision are the occipital protuberance, the spinal process of C2, the mastoid apex (MA), the transverse process of C1 (TPC1), and the root of the zygomatic arch.

The incision includes the suboccipital midline, it turns horizontally at the superior nuchal line, then it turns caudally toward the level of C2 close to the midpoint where it turns horizontal again toward the TPC1, where it heads rostrally passing the MA and to the level of the superior nuchal line where it ends, in a laying down S shape. If needed, the final leg of the incision can be extended around the ear and the pinna.

The lateral skin flap is dissected away from the muscle layer, while the medial is not. The midline incision is followed down in the avascular plane to the bone exposing the suboccipital midline, the posterior arch of C1, and the spinal process of C2.

If further lateral exposure is necessary, the muscles are elevated from the bone in a lateral to medial progression to expose the apex of the mastoid, the transverse process of the C1, the vertebral artery, and the occipital condyle.

Case Series Nine patients underwent surgery using this incision. All cases had a satisfactory intraoperative exposure. Eight patients (89.9%) presented no postoperative CSF leaks, minimal muscle atrophy, postoperative pain, dehiscences, or alopecia. One patient (11.1%), who had a preoperative folliculitis, presented with wound infection and required surgical revision after 3 months. Moderate muscle atrophy was noted in the long-term follow-up of this patient.

Discussion The S incision retracts the muscle bulge inferiorly and laterally, providing an open surgical field and the two skin flaps reduce tension on wound closure, leading to better healing. The manipulation of the muscles as a whole, avoiding incisions through them and excessive traction to move it away from the surgical field, leads to less muscle atrophy and pain in the postoperative period.

Conclusion This is an elegant incision and in our experience has been a successful and very useful approach for different patients and pathologies that required a far lateral approach to the skull base.