Table 4.

Summary of studies on mononeuropathy and focal neuropathy

Author, year	Country	Study design	Study funding/COI	No. of subjects	Diagnosis	Mean age (years)	Intervention	Outcomes
Zuidema et al. (2014) [51]	Netherlands	Case series	No funding	3	Neuropathic groin pain	36, 46, 39	DRG-S T11–L3	Case 1: After complete pain relief with trial, patient was implanted with DRG-S and at the follow-up period of 3 months, pain relief remained 100% (VAS 0 mm) Case 2: Pain relief remained at 100% at 3 months Case 3: VAS decreased to 1 cm within 1 week and was maintained at 2 months (90% pain relief)
Morgalla et al. (2017) [10]	Germany	Prospective with single arm	Investigator-initiated grant	34	Neuropathic groin pain from nerve injury of ilioinguinal or iliohypogastric nerve	50.4	DRG-S	30/34 pts were converted to permanent DRG-S. Results after 3 years were VAS decreased from median of 58 to 54.5. The PDI decreased from 548 to 523. The PCS changed from 531 to 516. The BPI dropped from 576 to 530. The BDI decreased from 517 to 57. Total of 5 patients had complications (16.7%)
Morgalla et al. (2019) [52]	Germany	Prospective with single arm	Multiple institutional funding sources	12	Unilateral localized neuropathic pain in the lower limbs or inguinal region	51.8 ± 6.05	DRG-S	At 1 and 6 months follow-ups, N2–P2 amplitudes were significantly greater and NRS scores significantly lower compared to baseline. There was a negative correlation between LEP amplitudes and NRS scores
Martin et al. (2020) [53]	UK	Retrospective	Grant funding from National Institute for Health Research Oxford Biomedical Research Centre	Total: 14 Single L3 lead: 8 Single L4 lead: 1 L3 and L4 leads: 3	Chronic neuropathic knee pain	49.2	DRG-S	Median preoperative NRS was 8.5 and median postoperative NRS was 2. The median improvement in pain score was 80%. All 12 pts were responders. Median coverage of pain area was 85%. 2 pts had their leads explanted: 1 for non-efficacy, and 1 for repeated electrode displacement
Schu et al. (2015) [9]	Germany (but other European states also involved)	Retrospective	No funding	29	Chronic groin pain: Post-herniorrhaphy (N = 12) and other etiology	> 18 years	T2–L2 DRG-S	25 pts (86.2%) received fully implantable DRG-S, average follow-up period was 27.8 ± 4.3 (SEM) weeks. The mean pain reduction was 71.4 ± 5.6%, and 82.6% (19/23) of pts experienced > 50% pain reduction at the last follow-up. A subgroup analysis of post-herniorrhaphy cohort also showed significant improvement
Hunter et al. (2017) [54]	USA	Case series	No funding	4	Post-amputation pain	59, 32, 67, 30	Selective stimulation of the DRG-S	Stimulating 1 or more DRG(s) produced paresthesia patterns that were contradictory to known dermatomal patterns. Upon completion of a 1-week trial, all 4 pts reported 60–90% pain relief, with coverage of the painful areas, and had permanent implant

BPI Brief Pain Inventory, BDI Beck Depression Inventory, COI conflict of interest, DRG dorsal root ganglion, DRG-S dorsal root ganglion stimulation, LEP laser-evoked potentials, PCS Pain Catastrophizing Scale, PDI Pain Disability Index, SCS spinal cord stimulation, SEM standard error of the mean, VAS visual analog scale