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Johannes Sarnthein, Nader Hejrati, Marian C. Neidert, Alexander M. Huber, and Niklaus Krayenbühl

Object

During surgeries that put the facial nerve at risk for injury, its function can be continuously monitored by transcranial facial nerve motor evoked potentials (FNMEPs) in facial nerve target muscles. Despite their advantages, FNMEPs are not yet widely used. While most authors use a 50% reduction in FNMEP response amplitudes as a warning criterion, in this paper the authors' approach was to keep the response amplitude constant by increasing the stimulation intensity and to establish a warning criterion based on the “threshold-level” method.

Methods

The authors included 34 consecutive procedures involving 33 adult patients (median age 47 years) in whom FNMEPs were monitored. A threshold increase greater than 20 mA for eliciting FNMEPs in the most reliable facial nerve target muscle was considered a prediction of reduced postoperative facial nerve function, and subsequently a warning was issued to the surgeon. Preoperative and early postoperative function was documented using the House-Brackmann grading system.

Results

Monitoring of FNMEPs was feasible in all 34 surgeries in at least one facial nerve target muscle. The mentalis muscle yielded the best results. The House-Brackmann grade deteriorated in 17 (50%) of 34 cases. The warning criterion was reached in 18 (53%) of 34 cases, which predicted an 83% risk of House-Brackmann grade deterioration. Sensitivity amounted to 88% (CI 64%–99%) and specificity to 82% (CI 57%–96%). Deterioration of FNMEPs and a worse House-Brackmann grade showed a high degree of association (p < 0.001). The impact of FNMEP monitoring on surgical strategy is exemplified in an illustrative case.

Conclusions

In surgeries that put the facial nerve at risk, the intraoperative increase in FNMEP stimulation threshold was closely correlated to postoperative facial nerve dysfunction. Monitoring of FNMEPs is a valid indicator of facial nerve function in skull base surgery. It should be used as an adjunct to direct electrical facial nerve stimulation and continuous electromyographic monitoring of facial nerve target muscles.

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Martin N. Stienen, Holger Joswig, Ivan Chau, Marian C. Neidert, David Bellut, Thomas Wälchli, Karl Schaller, and Oliver P. Gautschi

OBJECTIVE

The purpose of this study was to investigate whether the intraoperative application of an epidural steroid (ES) on the decompressed nerve root improves short- and midterm subjective and objective clinical outcomes after lumbar microdiscectomy.

METHODS

This study was a retrospective analysis of a 2-center database including consecutive cases in which patients underwent lumbar microdiscectomy. All patients who received ES application (40 mg triamcinolone, ES group) were matched by age and sex to patients who had not received ES application (control group). Objective functional impairment (OFI) was determined using age- and sex-adjusted T-scores of the Timed Up and Go (TUG) test. Back and leg pain (visual analog scale), functional impairment (Oswestry Disability Index [ODI], Roland-Morris Disability Index [RMDI], and health-related quality of life (hrQoL; 12-Item Short Form Health Survey [SF-12] physical component summary [PSC] score and EuroQol [EQ-5D index]) were measured at baseline, on postoperative day 3, and at postoperative week 6.

RESULTS

Fifty-three patients who received ES application were matched with 101 controls. There were no baseline demographic or disease-specific differences between the study groups, and preoperative pain, functional impairment, and hrQoL were similar. On postoperative day 3, the ES group had less disability on the RMDI (mean 7.4 vs 10.3, p = 0.003) and higher hrQoL as determined by the SF-12 PCS (36.5 vs 32.7, p = 0.004). At week 6, the ES group had less disability on the RMDI (3.6 vs 5.7, p = 0.050) and on the ODI by trend (17.0 vs 24.4, p = 0.056); better hrQoL, determined by the SF-12 PCS (44.3 vs 39.9, p = 0.018); and lower OFI (TUG test T-score 100.5 vs 110.2, p = 0.005). The week 6 responder status based on the minimum clinically important difference (MCID) was similar in the ES and control groups for each metric. The rates and severity of complications were similar, with a 3.8% and 4.0% reoperation rate in the ES group and control group, respectively (p = 0.272). There was a tendency for shorter hospitalization in the ES group (5.0 vs 5.8 days, p = 0.066).

CONCLUSIONS

Intraoperative ES application on the decompressed nerve root is an effective adjunct treatment that may lower subjective and objective functional impairment and increase hrQoL in the short and intermediate term after lumbar microdiscectomy. However, group differences were lower than the commonly accepted MCIDs for each metric, indicating that the effect size of the benefit is limited.

■ CLASSIFICATION OF EVIDENCE Type of question: therapeutic; study design: retrospective cohort trial; evidence: Class II.