Immediate effect of recurrent laryngeal nerve stimulation in patients with idiopathic unilateral vocal fold paralysis

Figures & data

Figure 1. Typical laryngoscopic images before and after recurrent laryngeal nerve stimulation in a male patient. (A) and (B) show vocal fold abduction and adduction before the stimulation, while (C) and (D) show vocal fold abduction and adduction after the stimulation. In each panel, the white dashed line represents the glottal midline, while the yellow and blue solid lines illustrate the other side of glottal angles for the healthy and paralyzed vocal folds, respectively.

Table 1. Summary data for comparison of the measures before and after RLN stimulation.

Measure	N	Mean ± Standard Deviation		Difference (After-Before)	Wilcoxon Signed Ranks Test		Percentage of Patients with improvement
					Z	p*
R	62	Before	1.531 ± 0.844	−0.390 ± 0.436	−5.448	<.001	67.74%
		After	1.140 ± 0.787
B	62	Before	1.368 ± 1.019	−0.435 ± 0.574	−4.799	<.001	62.90%
		After	0.932 ± 0.832
H	62	Before	1.660 ± 0.844	−0.431 ± 0.493	−5.280	<.001	70.97%
		After	1.229 ± 0.835
MPT	54	Before	8.827 ± 8.523	0.152 ± 3.379	1.069	.285	59.26%
		After	8.979 ± 8.465
DSI	49	Before	−0.223 ± 2.055	0.811 ± 1.473	3.606	<.001	73.47%
		After	0.588 ± 1.670
jitter	54	Before	1.039 ± 0.572	−0.199 ± 0.872	−2.559	.010	61.11%
		After	0.840 ± 0.736
shimmer	54	Before	3.325 ± 1.092	−0.328 ± 1.686	−2.036	.042	61.11%
		After	2.998 ± 1.281
NGAV	36	Before	0.264 ± 0.145	0.190 ± 0.116	5.216	<.001	97.22%
		After	0.454 ± 0.162
AGC	36	Before	9.479 ± 4.496	−3.359 ± 3.284	−4.642	<.001	80.56%
		After	6.120 ± 3.994

*p < 0.05 in bold denote statistical significance. Abbreviations: RLN: recurrent laryngeal nerve; MPT: maximum phonation time; DSI: dysphonia severity index; NGAV: normalized glottal angle variation; AGC: angle of glottal closure.

Table 2. Comparison of stimulation effect on selected measures in different gender groups.

Difference of measure	Mean ± Standard Deviation		Mann–Whitney U-test
	Male	Female	Z	p*
ΔR	−0.363 ± 0.446	−0.420 ± 0.431	0.801	.423
ΔB	−0.381 ± 0.520	−0.493 ± 0.631	0.769	.442
ΔH	−0.363 ± 0.464	−0.503 ± 0.520	1.272	.203
ΔMPT	0.277 ± 3.594	−0.005 ± 3.159	−0.479	.632
ΔDSI	0.887 ± 1.406	0.717 ± 1.579	0.332	.740
Δjitter	0.073 ± 0.918	−0.538 ± 0.687	3.064	.002
Δshimmer	−0.269 ± 1.795	−0.401 ± 1.575	0.444	.657
ΔNGAV	0.187 ± 0.107	0.193 ± 0.127	−0.047	.962
ΔAGC	−2.835 ± 2.621	−3.883 ± 3.841	0.475	.635

*p < 0.05 in bold denote statistical significance. Abbreviations: MPT: maximum phonation time; DSI: dysphonia severity index; NGAV: normalized glottal angle variation; AGC: angle of glottal closure.

Table 3. Correlation between changes in different measures using a simple linear regression model.

R^2 *	ΔR	ΔB	ΔH	ΔDSI	Δjitter	Δshimmer	ΔNGAV	ΔAGC
ΔR	1.000	0.428	0.754	0.006	0.000	0.003	0.021	0.110
ΔB		1.000	0.559	0.069	0.001	0.056	0.002	0.118
ΔH			1.000	0.001	0.000	0.004	0.014	0.093
ΔDSI				1.000	0.000	0.018	0.047	0.076
Δjitter					1.000	0.198	0.066	0.033
Δshimmer						1.000	0.002	0.019
ΔNGAV							1.000	0.029
ΔAGC								1.000

*R² with statistical significance (p < 0.05) are highlighted in bold. Abbreviations: MPT: maximum phonation time; DSI: dysphonia severity index; NGAV: normalized glottal angle variation; AGC: angle of glottal closure.

Table 4. Multiple linear regression between stimulation effects and pre-stimulation measures.

Stimulation effects	Standardized coefficients of selected measures before RLN stimulation*							R^2 *
	$\overline{\mathit{\text{RBH}}}$	MPT	DSI	jitter	shimmer	NGAV	AGC
ΔR	−0.944	0.315	−0.556	0.139	0.293	−0.173	−0.023	0.475
ΔB	−0.608	0.437	−0.395	0.070	0.089	−0.067	−0.186	0.636
ΔH	−0.857	0.492	−0.749	0.171	0.177	−0.232	−0.046	0.462
ΔM	−0.357	−0.511	−0.234	−0.007	−0.061	−0.087	0.087	0.314
ΔDSI	−0.490	0.175	−1.082	−0.060	0.174	−0.124	−0.010	0.577
Δjitter	0.252	0.132	−0.009	−0.839	0.033	−0.064	−0.058	0.629
Δshimmer	0.691	0.243	−0.001	−0.044	−0.783	0.189	−0.318	0.706
ΔNGAV	0.115	0.083	0.023	−0.389	−0.100	−0.258	0.082	0.231
ΔAGC	−0.362	0.291	−0.711	−0.114	0.295	−0.145	−0.671	0.532

*Coefficients and R² with statistical significance (p < 0.05) are highlighted in bold. Abbreviations: RBH, mean value of R, B, and H scales; MPT: maximum phonation time; DSI: dysphonia severity index; NGAV: normalized glottal angle variation; AGC: angle of glottal closure.