Table 2.

The treatment protocol of nerve stimulation in each study.

Study (year)	Group	Treatment protocol	Stimulation parameters	Electrode size	Location of electrode	Stimulator	Current range
Ramírez-García (2019)	TTNS	30 min/wk, for 12 wk	Biphasic square waves, 20 Hz and 200 cycles	32 mm	5 cm above the medial malleolus	TENS URO stim2	0.5–20 mA
	PTNS	30 min/wk, for 12 wk	Biphasic square waves, 20 Hz and 200 cycles	40 mm × 0.20 mm acupuncture needles (34 gauge)	Percutaneous insertion of a needle 5 cm above the medial malleolus	TENS URO stim2	0.5–20 mA
Martin-Garcia (2019)	TTNS	≥30 min × 3/wk, for 6 mo	20 Hz and 200 cycles	30 mm	Three finger-breaths cranial to the medial malleolus	NeuroTrac Pelvitone	0–20 mA
	PTNS	30 min/4 wk, for 6 mo	20 Hz and 200 cycles	40 mm × 0.20 mm acupuncture needles (34 gauge)	Three finger-breaths cranial to the medial malleolus	AS SUPER 4 digital	0–20 mA
Alfonso Barrera (2013)	TTNS	30 min/wk, for 12 wk	20 Hz and 200 cycles	–	3 to 4 cm above the medial malleolus	Stimulator NeuroTrac	0–10 mA
	PTNS	30 min/wk, for 12 wk	20 Hz and 200 cycles	34-gauge needle	Percutaneous insertion of a needle 3–4 cm above the medial malleolus	Stimulator Urgent	0–10 mA
Maurelli (2012)	TTNS	30 min/wk, for average 19.7 mo	20 Hz and 200 cycles	–	5 cm above the medial malleolus	LogiSTIM	0–10 mA
	PTNS	30 min/wk	20 Hz and 200 cycles	40 mm × 0.20 mm acupuncture needles (34 gauge)	Percutaneous insertion of a needle 5 cm above the medial malleolus	LogiSTIM	0–10 mA