Tailored Traction and Monopolar Stimulation Help Preserve the Frontotemporal Branches of the Facial Nerve During Cranial Base Approaches.

BACKGROUND AND

OBJECTIVES

Preservation of the frontotemporal branches of the facial nerve (FTB of CN VII) is essential to prevent frontalis muscle dysfunction after anterolateral skull base surgery. Although anatomical integrity of the FTB of CN VII is often preserved, patients may still experience frontalis palsy, suggesting that nontransectional mechanisms may contribute to neuropraxia. In this study, we describe the use of intraoperative neurophysiological monitoring combined with refined, tension-conscious retraction techniques to mitigate iatrogenic injury to the FTB.

METHODS

A total of 38 patients undergoing anterolateral skull base approaches were enrolled in this study. Within the intervention group, 18 patients underwent monopolar stimulation to assess the response of the FTB of CN VII in combination with a tailored retraction technique. Frontalis muscle contractions were evaluated before and after the placement of scalp retraction hooks, and the incidence of postoperative frontalis palsy was compared with a control group. In addition, mechanical testing was conducted to measure the strain on the retraction hooks at various elongation points.

RESULTS

Mechanical tensile testing showed that elongating the retraction hook tube to double its original length generated a force of 10.2 N. During stimulation, frontalis muscle contractions were visible but diminished when retraction forces exceeded 10.2 N (100% strain). Immediately after surgery, no patients in the intervention group developed frontalis palsy, compared with 5 in the control group (0.0% vs 33.3%, P = .04). At 3-month follow-up, no patients in the intervention group had frontalis palsy, compared with 3 in the control group (0.0% vs 10.0%, P = .23).

CONCLUSION

This study demonstrates the utility of neuromonitoring with tailored retraction to prevent postoperative frontalis palsy. A 1-cm extension of the retraction hook tubing signals excessive tension, and incision extension at this point helps decrease the force on the cutaneous flap and preserve nerve function.