Investigation into the Effectiveness of Combining Transcranial Direct Current Stimulation and Transcutaneous Electrical Nerve Stimulation as Treatment Options for Poststroke Shoulder Pain by Utilizing Functional Near-Infrared Spectroscopy

Figures & data

Figure 1 Schematic overview of the whole study.

Abbreviations: VAS, Visual Analogue Scale; CPT, current perception thresholds; PTT, pain tolerance threshold; fNIRS, functional near-infrared spectroscopy.

Figure 2 (A) Neurometer CPT/C sensory neuroquantitative assay. (B) The electrode is placed on the affected shoulder.

Figure 3 (A) Scene of fNIRS testing. (B) Brain localization schema of channels. (C) fNIRS testing procedure.

Abbreviation: PTT, pain tolerance threshold.

Table 1 Demographics and Baseline Evaluations

Characteristics	TENS	tDCS	tDCS+TENS	F/X^2	P-value
Age (years, x±s)	64.09±8.11	63.33±8.16	63.64±8.59	0.02	0.979
Gender n(%)				0.30^#	1.000
Male	9(81.8)	7(77.8)	9(81.8)
Female	2(18.2)	2(22.2)	2(18.2)
Hemiplegia side n(%)				0.34^#	1.000
Left	6(54.5)	5(55.6)	7(63.6)
Right	5(45.5)	4(44.4)	4(36.4)
Duration of disease(Months)	6.82±4.56	7.00±4.03	7.18±4.51	0.02	0.981
Pain Duration (Months)	5.45±3.67	5.56±3.58	5.55±3.56	0.003	0.997
Type of stroke n(%)				2.69^#	0.288
Ischemic	8(72.7)	8(88.9)	6(54.5)
Hemorrhagic	3(27.3)	1(11.1)	5(45.5)
VAS	5.45±2.30	6.00±2.06	5.55±2.02	0.18	0.84
CPT-2K Hz	178.00±62.09	146.67±47.57	149.00±42.26	1.21	0.314
CPT-250 Hz	50.91±8.81	48.22±18.75	48.09±14.56	0.13	0.876
CPT-5 Hz	42.82±18.42	37.67±21.91	43.18±20.31	0.23	0.800
PTT-2K Hz	17.45±2.73	17.33±3.94	16.73±3.72	0.14	0.873
PTT-250 Hz	11.82±2.73	12.56±4.67	11.55±4.44	0.14	0.872
PTT-5 Hz	20.45±4.61	19.00±6.63	19.91±6.55	0.15	0.862

Note: ^#Fisher exact test.

Abbreviations: TENS, Transcutaneous Electrical Nerve Stimulation; tDCS, Transcranial Direct Current Stimulation; VAS, Visual Analogue Scale; CPT, Current perception threshold; PTT, Pain tolerance threshold.

Table 2 Visual Analogue Scale Values Before and After Intervention in the Three Groups (Intra-Group and Inter-Group Differences)

Variables (VAS)	n	Pre-Treatment	Post-Treatment	Mean Difference (95% CI)	t-Test
					t	P-value
TENS	11	5.45±2.30	3.18±2.18	−2.27(−3.62~−0.93)	3.76	0.004*
tDCS	9	6.00±2.06	4.33±2.12	−1.67(−2.94~−0.39)	3.02	0.017*
tDCS+TENS	11	5.55±2.02	1.64±1.29	−3.91(−4.78~−3.04)	9.97	<0.001*

Note: *P<0.05.

Abbreviations: VAS, Visual Analogue Scale; TENS, Transcutaneous Electrical Nerve Stimulation; tDCS, Transcranial Direct Current Stimulation.

Figure 4 (A) Changes in Visual Analogue Scale Values between post and pre stimulation. (B) Changes in current perception threshold and pain tolerance threshold between post and pre stimulation. (C) Changes in the average HbOμm of channel 38 when performing PTT2K between post and pre stimulation.

Table 3 Sensory and Pain Thresholds Measurements Before and After Intervention in the Three Groups (Intra-Group and Inter-Group Differences)

Variables	Group	n	Pre-Treatment	Post-Treatment	Mean Difference (95% CI)	t-Test
						t	P-value
CPT-2K Hz	TENS	11	178.00±62.09	173.36±56.26	−4.64(−37.26~27.99)	0.32	0.758
	tDCS	9	146.67±47.57	158.11±42.86	11.44(−23.16~46.05)	0.76	0.468
	tDCS+TENS	11	149.00±42.26	169.55±44.49	20.55(−10.35~51.44)	1.48	0.169
CPT-250 Hz	TENS	11	50.91±8.81	51.09±15.46	0.18(−11.53~11.90)	0.04	0.973
	tDCS	9	48.22±18.75	47.11±21.95	−1.11(−20.12~17.90)	0.14	0.896
	tDCS+TENS	11	48.09±14.56	44.18±15.20	−3.91(−15.80~7.98)	0.73	0.481
CPT-5 Hz	TENS	11	42.82±18.42	41.27±16.22	−1.55(−13.47~10.38)	0.29	0.779
	tDCS	9	37.67±21.91	31.33±10.04	−6.33(−24.55~11.88)	0.80	0.446
	tDCS+TENS	11	43.18±20.31	36.45±18.72	−6.73(−19.30~5.85)	1.19	0.261
PTT-2K Hz	TENS	11	17.45±2.73	15.82±3.79	−1.64(−4.44~1.17)	1.30	0.223
	tDCS	9	17.33±3.94	18.33±3.57	1.00(−1.31~3.31)	1.00	0.347
	tDCS+TENS	11	16.73±3.72	17.27±3.82	0.55(−2.01~3.10)	0.48	0.645
PTT-250 Hz	TENS	11	11.82±2.73	10.64±5.14	−1.18(−4.78~2.42)	0.73	0.482
	tDCS	9	12.56±4.67	12.44±4.16	− 0.11(−2.73~2.51)	0.10	0.924
	tDCS+TENS	11	11.55±4.44	11.55±4.55	0.00(−1.04~1.04)	0.00	1.000
PTT-5 Hz	TENS	11	20.45±4.61	18.36±6.02	−2.09(−7.00~2.81)	0.95	0.365
	tDCS	9	19.00±6.63	20.44±6.39	1.44(−1.84~4.73)	1.01	0.340
	tDCS+TENS	11	19.91±6.55	18.27±7.25	−1.64(−3.99~ 0.72)	1.55	0.151

Abbreviations: CPT, current perception threshold; PTT, pain tolerance threshold.

Figure 5 (A) Comparison of changes before and after tDCS+ TENS stimulation in brain activation when performing PTT 2 KHz. (B) Comparison of changes before and after TENS stimulation in brain activation when performing PTT 250 Hz. (C) Comparison of changes before and after tDCS stimulation in brain activation when performing PTT 250 Hz. (D) Comparison of changes before and after tDCS+ TENS stimulation in brain activation when performing PTT 250 Hz. (E) Comparison of changes before and after tDCS stimulation in brain activation when performing PTT 5 Hz. (F) Comparison of changes before and after tDCS+ TENS stimulation in brain activation when performing PTT 5 Hz. (G) Comparison of difference in brain activation when performing PTT 2 KHz task immediately after stimulation.

Abbreviations: PTT, pain tolerance threshold; TENS, Transcutaneous Electrical Nerve Stimulation; tDCS, Transcranial Direct Current Stimulation.