J Neurol Surg B Skull Base 2019; 80(06): 599-603
DOI: 10.1055/s-0038-1677538
Original Article
Georg Thieme Verlag KG Stuttgart · New York

Estimation of Intraoperative Stimulation Threshold of the Facial Nerve in Patients Undergoing Microvascular Decompression

Rafey A. Feroze*
1   Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
,
Michael M. McDowell*
1   Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
,
Jeffrey Balzer
1   Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
,
Donald J. Crammond
1   Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
,
Partha Thirumala
1   Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
,
Raymond F. Sekula Jr.
1   Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
› Author Affiliations
Funding Statement The authors did not receive any grant funding from any agencies in the public, commercial, or not-for-profit sectors.
Further Information

Publication History

25 June 2018

09 December 2018

Publication Date:
29 January 2019 (online)

Abstract

Introduction Facial weakness can result from surgical manipulation of the facial nerve. Intraoperative neuromonitoring reduces functional impairment but no clear guidelines exist regarding interpretation of intraoperative electrophysiological results. Most studies describe subjects with facial nerves encumbered by tumors or those with various grades of facial nerve weakness. We sought to obtain the neurophysiological parameters and stimulation threshold following intraoperative facial nerve triggered electromyography (t-EMG) stimulation during microvascular decompression for trigeminal neuralgia to characterize the response of normal facial nerves via t-EMG.

Methods Facial nerve t-EMG stimulation was performed in seven patients undergoing microvascular decompression for trigeminal neuralgia. Using constant current stimulation, single stimulation pulses of 0.025 to 0.2 mA intensity were applied to the proximal facial nerve. Compound muscle action potentials, duration to onset, and termination of t-EMG responses were recorded for the orbicularis oculi and mentalis muscles. Patients were evaluated for facial weakness following the surgical procedure.

Results Quantifiable t-EMG responses were generated in response to all tested stimulation currents of 0.025, 0.05, 0.1, and 0.2 mA in both muscles, indicating effective nerve conduction. No patients developed facial weakness postoperatively.

Conclusions The presence of t-EMG amplitudes in response to 0.025 mA suggests that facial nerve conduction can take place at lower stimulation intensities than previously reported in patients with tumor burden. Proximal facial nerve stimulation that yields responses with thresholds less than 0.05 mA may be a preferred reference baseline for surgical procedures within the cerebellopontine angle to prevent iatrogenic injury.

* Both authors contributed equally.


 
  • References

  • 1 Danner CJ. Facial nerve paralysis. Otolaryngol Clin North Am 2008; 41 (03) 619-632 , x
  • 2 Dew LA, Shelton C. Iatrogenic facial nerve injury: prevalence and predisposing factors. Ear Nose Throat J 1996; 75 (11) 724-729
  • 3 Sughrue ME, Yang I, Rutkowski MJ, Aranda D, Parsa AT. Preservation of facial nerve function after resection of vestibular schwannoma. Br J Neurosurg 2010; 24 (06) 666-671
  • 4 Fenton JE, Chin RY, Shirazi A, Fagan PA. Prediction of postoperative facial nerve function in acoustic neuroma surgery. Clin Otolaryngol Allied Sci 1999; 24 (06) 483-486
  • 5 Harner SG, Daube JR, Ebersold MJ, Beatty CW. Improved preservation of facial nerve function with use of electrical monitoring during removal of acoustic neuromas. Mayo Clin Proc 1987; 62 (02) 92-102
  • 6 Kaylie DM, Gilbert E, Horgan MA, Delashaw JB, McMenomey SO. Acoustic neuroma surgery outcomes. Otol Neurotol 2001; 22 (05) 686-689
  • 7 Nissen AJ, Sikand A, Curto FS, Welsh JE, Gardi J. Value of intraoperative threshold stimulus in predicting postoperative facial nerve function after acoustic tumor resection. Am J Otol 1997; 18 (02) 249-251
  • 8 Bernat I, Grayeli AB, Esquia G, Zhang Z, Kalamarides M, Sterkers O. Intraoperative electromyography and surgical observations as predictive factors of facial nerve outcome in vestibular schwannoma surgery. Otol Neurotol 2010; 31 (02) 306-312
  • 9 Grabb PA, Albright AL, Sclabassi RJ, Pollack IF. Continuous intraoperative electromyographic monitoring of cranial nerves during resection of fourth ventricular tumors in children. J Neurosurg 1997; 86 (01) 1-4
  • 10 Kombos T, Suess O, Kern BC, Funk T, Pietilä T, Brock M. Can continuous intraoperative facial electromyography predict facial nerve function following cerebellopontine angle surgery?. Neurol Med Chir (Tokyo) 2000; 40 (10) 501-505 , discussion 506–507
  • 11 Kirkpatrick PJ, Watters G, Strong AJ, Walliker JR, Gleeson MJ. Prediction of facial nerve function after surgery for cerebellopontine angle tumors: use of a facial nerve stimulator and monitor. Skull Base Surg 1991; 1 (03) 171-176
  • 12 Sughrue ME, Kaur R, Kane AJ. , et al. The value of intraoperative facial nerve electromyography in predicting facial nerve function after vestibular schwannoma surgery. J Clin Neurosci 2010; 17 (07) 849-852
  • 13 Goldbrunner RH, Schlake HP, Milewski C, Tonn JC, Helms J, Roosen K. Quantitative parameters of intraoperative electromyography predict facial nerve outcomes for vestibular schwannoma surgery. Neurosurgery 2000; 46 (05) 1140-1146 , discussion 1146–1148
  • 14 Thirumala P, Frederickson AM, Balzer J. , et al. Reduction in high-frequency hearing loss following technical modifications to microvascular decompression for hemifacial spasm. J Neurosurg 2015; 123 (04) 1059-1064
  • 15 Hughes MA, Branstetter BF, Taylor CT. , et al. MRI findings in patients with a history of failed prior microvascular decompression for hemifacial spasm: how to image and where to look. AJNR Am J Neuroradiol 2015; 36 (04) 768-773
  • 16 Thirumala PD, Mohanraj SK, Habeych M. , et al. Value of free-run electromyographic monitoring of lower cranial nerves in endoscopic endonasal approach to skull base surgeries. J Neurol Surg B Skull Base 2012; 73 (04) 236-244
  • 17 Thirumala PD, Kassasm AB, Habeych M. , et al. Somatosensory evoked potential monitoring during endoscopic endonasal approach to skull base surgery: analysis of observed changes. Neurosurgery 2011; 69 (1, Suppl Operative) ons64-ons76 , discussion ons76
  • 18 Acioly MA, Liebsch M, de Aguiar PH, Tatagiba M. Facial nerve monitoring during cerebellopontine angle and skull base tumor surgery: a systematic review from description to current success on function prediction. World Neurosurg 2013; 80 (06) e271-e300