Neural outcomes after plasma knife dissection: a pathologic study and clinical correlation

The initial aim was to determine the rate of pathologic tissue damage when dissecting the rat sciatic nerve with either bipolar forceps or low-temperature tripolar plasma knife. The second aim was to determine the safety and effectiveness of the plasma knife during parotid surgery.

A prospective, randomized, single-blind study was performed on 40 rat sciatic nerves dissected by either bipolar electrocautery with a cold knife or a plasma knife. Dissected nerves were excised and submitted blindly to pathology for analysis of nerve injury. The degree of nerve trauma was graded by the Carlander nerve injury classification. Separately, a review was performed on the facial nerve outcomes of 30 patients who underwent plasma knife parotidectomy.

No thermal or neural injury was noted in the 40 rat sciatic nerves dissected by either bipolar electrocautery or plasma knife (p = 1.0). Two plasma knife-dissected nerves (8%) demonstrated significant numbers of mast cells in the perineural soft tissue. In 30 patients undergoing plasma knife-parotidectomy, 10 (33%) had mild weakness of 1 or 2 preserved facial nerve branch postoperatively (House-Brackmann 2) that resolved within 1 month, whereas 2 (7%) had visible weakness in 1 branch (HB 3) that normalized after 3 months of follow-up.

Plasma knife nerve dissection seems to be a safe and effective alternative to conventional methods. This technique may confer some advantages over conventional methods with the ability to simultaneously cut and coagulate tissue with minimal thermal spread and electrical stimulation of adjacent neural structures.