Intraoperative nerve stimulation for lesion localization in pediatric acute traumatic facial paralysis: A pilot study of the Ulusoy technique

Authors

Abstract

Introduction This study aimed to evaluate the effectiveness of intraoperative nerve stimulation as a novel diagnostic technique for accurately localizing the site of nerve injury in acute peripheral facial paralysis (PFP).
Case Presentation This study included two patients presenting with acute-onset complete PFP. Intraoperative facial nerve stimulation was performed sequentially along the nerve’s course. Localization of the injured segment was based on the absence of proximal stimulation response in the affected area, while responses remained intact distal to the lesion. In both cases, the site of neural injury was accurately identified using intraoperative stimulation. The findings enabled targeted and limited decompression of the facial nerve.
Conclusion This is the first study to demonstrate the potential of intraoperative nerve stimulation as a reliable technique for lesion localization in traumatic complete PFP. Accurate identification of the affected segment can optimize surgical outcomes by enabling precise, minimally invasive decompression.

Keywords

Introduction

Traumatic facial nerve paralysis (FNP) is a complex condition that requires a multidisciplinary approach for accurate diagnosis and management [1, 2]. It occurs in 7-10% of patients with temporal bone fractures [3]. However, the indications and timing for surgical intervention in cases of FNP caused by temporal bone fractures remain controversial [4]. Traumatic FNP is classified as early or late based on the onset of paralysis after injury; paralysis developing within 24 to 72 hours is considered the acute form [1, 3]. There is no consensus regarding treatment when a displaced fracture line in the facial nerve canal is not observed. In this situation, the physician’s clinical experience and the patient’s or their parents’ choices (once they are informed about the process) are generally significant.
Facial nerve integrity monitoring is routinely employed by many surgeons during otologic procedures to ensure intraoperative nerve preservation. There are no data in PubMed regarding the use of intraoperative nerve stimulation for lesion localization in acute peripheral facial paralysis. In this study, we present two pediatric cases in which a novel technique (Ulusoy Technique) was utilized to localize the site of nerve injury in acute peripheral facial paralysis, highlighting its potential diagnostic value and clinical outcomes.

Case Presentation

Case 1
A 9-year-old boy presented with left-sided acute complete peripheral FNP (House-Brackmann (HB) grade VI) following blunt trauma to his head while he was playing football with his friends (Figure 1A).
Otoscopic examination revealed marginal perforation of the tympanic membrane in the anterosuperior quadrant. High-resolution CT (HRCT) of the temporal bone identified a nondisplaced fracture extending to the geniculate ganglion (GG) (Figure 2). Surgical decompression was elected without waiting for electroneuronography (ENoG), based on the acute onset and severity of paralysis.
Intraoperatively, after canal wall up tympanomastoidectomy and posterior tympanotomy, each facial nerve segment was stimulated, starting from the GG level and proceeding distally, with 0.8 mA using a monopolar stimulator probe (NIM- Response® 3.0 Medtronic Xomed Inc., Jacksonville, FL 32216- 0980 USA). The presence of visible facial muscle contraction and/or electromyography (EMG) waveform was accepted as an indicator of functional nerve conduction. Nerve stimulation was not seen in the GG and tympanic segments, while nerve stimulation was seen in the second genu and the proximal part of the mastoid segment. After decompression of the fallopian canal at the geniculate ganglion and tympanic segments, the intraoperative nerve integrity monitor (NIM) findings were once again confirmed. The perineurium was edematous in the tympanic and GG segments. As a result, decompression was completed by making an incision in the perineurium only in these two segments. This targeted approach reduced operative time and minimized surgical morbidity.
The patient was followed up with monthly EMG in the postoperative period, and complete functional recovery (HB grade I) was achieved in the fifth month (Figure 1B).
Case 2
A 3-year-old male patient presented with right-sided acute complete peripheral facial paralysis (HB grade VI) after striking his head on a stove while running. HRCT revealed no apparent fractures involving the facial nerve canal (Figure 3).
Due to the acute complete peripheral facial paralysis following trauma, and the patient’s presentation within the first six hours, a decision was made to perform facial nerve decompression without awaiting ENoG. Intraoperatively, a longitudinal fracture line was observed along the epitympanum, perpendicular to the GG, and a second fracture line was noted parallel to the tympanic segment of the fallopian canal. Using the same stimulation protocol as in Case 1, no evoked response was detected in the first three segments, while a positive response was recorded distal to the second genu.
Facial nerve decompression was performed from the GG to the 2 mm area distal to the second genu. At this stage, the NIM findings were reconfirmed by reapplying stimulation and verifying the absence of a response. This technique enabled precise lesion localization and avoided unnecessary decompression of the mastoid segment. After identifying the lesion site, an incision was performed on the perineurium. The patient was followed up with monthly EMG, and a complete functional recovery (HB grade I) was achieved in the 6th month.
Ethical Approval
Ethical approval was obtained from the Ethics Committee of Selçuk University (Date: 2025-02-25, No: 2025/125). Informed consent was obtained from all patients for the scientific use of their data.

Discussion

The most significant finding of this study is the determination of accurate localization of the injured site in both pediatric patients with acute traumatic peripheral facial paralysis using the novel technique we describe. This novel technique has the potential to become a promising method in enabling minimally invasive management of acute traumatic facial paralysis.
Emergency surgical intervention is generally recommended for cases of acute complete FNP secondary to trauma, whereas delayed-onset cases are usually managed conservatively [3]. Hato et al. reported a 92.9% recovery rate to HB grade I or II following decompression within two weeks in patients with severe acute traumatic FNP [3]. The standard criteria for surgical intervention include onset of paralysis within 14 days, greater than 90% degeneration on ENoG, and absent activity on EMG [2, 3].
Trauma may lead to perineural edema, vascular congestion, partial or complete rupture, and degeneration of the facial nerve [2]. In such cases, surgical decisions regarding the extent of decompression and the need for nerve repair depended on subjective microscopic evaluations of the facial nerve during exploration, which do not entirely reflect the physiological status of the nerve fibers [4]. Therefore, more specific criteria are needed to guide clinical decision-making [4]. Furthermore, the success of surgical decompression depends on accurately identifying the injured nerve segment [5].
Modern diagnostic tools, such as HRCT of the temporal bone and advanced electrophysiological tests, are employed to plan the appropriate treatment strategy [4]. Electrophysiological tests play an essential role in demonstrating the degree of nerve damage and the stages of nerve degeneration and regeneration [1]. ENoG, nerve excitatory test (NET), and maximal stimulation test (MST) may be used to evaluate acute complete paralysis while the nerve is in the degeneration phase. These tests provide accurate information in the first 3 weeks and are not used in the first three days because Wallerian degeneration has not yet reached the stylomastoid foramen [1]. EMG plays a supportive role within the first 14 days following the onset of acute paralysis and is particularly valuable for assessing chronic paralysis after the third week [1].
Due to the inability to perform electrophysiological tests like ENoG within the first 72 hours, deferring intervention during this time may lead to missing the crucial therapeutic window in cases of actual nerve injury. In such cases, many clinicians make decisions based on HRCT findings of the temporal bone and carry out decompression if a displaced fracture is identified along the course of the facial nerve.
As part of standard practice in many otologic procedures, intraoperative facial nerve monitoring is routinely employed. However, the use of a nerve integrity monitor is not routine in patients with facial nerve paralysis. We routinely use facial nerve monitoring in patients undergoing facial nerve decompression. In a case of acute traumatic complete peripheral FNP, we decided to perform decompression following the family’s informed consent. Intraoperative findings during this case prompted the development of a novel method for determining lesion localization. Considering that Wallerian degeneration takes approximately 72 hours to reach the stylomastoid foramen, we hypothesized that an early intraoperative nerve stimulation method may allow real-time identification of the damaged segment.
Using a monopolar stimulator probe, we stimulated the facial nerve sequentially from the GG distally. In the first patient, no evoked response was detected in the GG and tympanic segments, whereas positive responses were obtained in the second genu and proximal mastoid segments (Case 1). The same method was successfully applied in a second case, confirming its potential diagnostic value in the early period of complete traumatic FNP (Case 2).
Although intraoperative facial nerve stimulation is commonly used in neurotologic surgeries (e.g., for cerebellopontine angle tumors or tympanomastoidectomy), there is a deficiency of literature on its use in traumatic facial palsy surgery. Notably, Gantz et al. briefly discussed the method in the 1980s for Bell’s palsy, suggesting it may outperform the Schirmer test in lesion localization [5, 6]. To date, no clinical applications of this technique have been reported in traumatic cases. This report is, to our knowledge, the first to clinically validate the use of intraoperative nerve stimulation for accurately identifying lesion sites in acute traumatic peripheral facial paralysis.

Limitations

This study has several limitations that should be acknowledged. The small number of patients is the most important limitation. Larger, prospective, multicenter studies are needed to validate the reliability, reproducibility, and clinical utility of this novel approach.

Conclusion

This preliminary study suggests that this technique may be a potentially important diagnostic tool in determining the area of nerve damage in acute complete PFP following trauma. Accurate identification of the damaged segment will allow decompression to be performed at the correct location and to a minimal extent, thereby providing an opportunity for personalized treatment. In addition, it may help us define this region in cases where nerve integrity is preserved despite axonal damage. In some cases of traumatic peripheral facial paralysis, although the perineurium appears intact, a reduction in nerve diameter compared to adjacent segments may become evident upon perineurial incision. In such cases, precise identification of the damaged segment can significantly reduce operative time and surgical morbidity. Although the preliminary findings of this study are promising, multicenter studies are needed to elucidate issues such as the diagnostic reliability and reproducibility of the technique.

References

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