Dorsal Root Ganglion Stimulation Relieves Chronic Neuropathic Pain Along With a Decrease in Cortical γ Power.

BACKGROUND: Stimulation of dorsal root ganglion (DRG) is an ideal neuromodulative intervention, providing pain relief in localized chronic pain conditions because γ-band oscillations reflect the intensity of ongoing chronic pain in patients affected. OBJECTIVE: We aimed to observe the role of cortical γ-band power associated with the relief of chronic neuropathic pain through DRG stimulation (DRGS). MATERIALS AND METHODS: We examined nine patients (two women, mean age 56.8 years; range, 36-77 years) diagnosed with chronic neuropathic pain who underwent DRGS therapy. We used the numeric rating scale (NRS) on the painful limb and simultaneously recorded the electroencephalography to assess the broadband γ power. Assessments were conducted on the first day and on the seventh day after implantation of the DRGS system and then compared and correlated with the results of the NRS. RESULTS: The NRS scores showed a significant decrease from the first day to the seventh day (p = 0.007). The resting-state γ power revealed a significant decrease (p = 0.021) between 30 and 45 Hz, recorded through the central electrode contralateral to the painful limb from the first day (mean [M] = 0.46, SD = 0.25) to the seventh day (M = 0.31, SD = 0.12) after DRGS. There was no significant change in the resting-state γ-band power recorded through the central electrode ipsilateral to the painful limb. However, we found a positive correlation in the γ-band power (rs = 0.628, p = 0.005) with the NRS rating. CONCLUSIONS: A lateralized decrease in broadband γ power may be considered further evidence supporting a reduction in the hyperexcitability of the nociceptive system in response to DRGS therapy. In the future, γ-band power could serve as a biomarker for assessing the efficacy of DRGS during the seven-day test phase preceding the implantation of the DRGS system.

Is it possible to generate an additional pleasant and pain-relieving muscle stimulation when using a low-frequency spinal cord stimulation (SCS) for the treatment of lower back pain? Pilot study: A new technique: "MuscleSCS".

OBJECTIVE: The combined use of spinal cord stimulation (SCS) and muscle stimulation, in the treatment of chronic pain, using the same probe, could improve the clinical results. However, this technique has not been established as yet. It was our hypothesis that it is possible to generate muscle stimulation by using low frequencies with SCS electrodes and use it to additionally treat chronic back pain. METHODS: We generated muscle stimulation in patients with previously implanted SCS electrodes, for the treatment of lower back pain, by using low frequencies (2, 4, 6, and 8 Hz) and different contact combinations of the electrodes. The results were evaluated by using visual inspection (videos), haptic control, surface electromyography (EMG), and sonographic recordings. RESULTS: This pilot study (17 patients, seven females, age 36-87 years, 11 percutaneous paddle leads, and 6 octrodes) was performed at the Neurosurgical Department of the University of Tuebingen. The most preferred frequencies were 6 Hz (45.5% of percutaneous paddle leads) and 8 Hz (50% of octrodes) at contacts 3&4 or 5&6. The preference of frequencies differed significantly among genders (p = 0.023). Simultaneous EMG and ultrasonic recordings demonstrated the generation of muscle potentials and the stimulation of deeper muscle groups. CONCLUSION: In this study, it has been shown that with low-frequency SCS stimulation, pleasant and pain-relieving muscle contractions of the lower and upper back can also be generated. This combined method has been coined by us as "MuscleSCS" technique. Clinical trials are necessary to establish the value of this combined technique and its subtypes.

Analysis of Somatosensory Profiles Using Quantitative Sensory Testing During Tonic and BurstDR Stimulation for the Treatment of Chronic Pain.

BACKGROUND: In the presence of neuropathic pain, other sensory qualities, such as touch or pressure, which are a sign of nerve damage, are almost always affected. However, it is unclear to which extent spinal cord stimulation (SCS) influences these simultaneously damaged sensory pathways or possibly contributes to their regeneration. OBJECTIVES: The aim of this study was to investigate the effects and possible differences of tonic and BurstDR (Abbott, Austin, TX) SCS on somatosensory profiles of patients with chronic neuropathic pain, using quantitative sensory testing (QST). STUDY DESIGN: A randomized, single-blinded, single-center study. SETTING: University medical center. METHODS: After a washout phase of 4 hours and having done the basic QST measurement, either tonic or BurstDR stimulation was performed for 30 minutes in a randomized fashion. Then, the second measurement was taken. The third measurement followed after using the remaining stimulation mode for 30 minutes. Mean values of all QST parameters were calculated and compared. We also computed Z-values using standard data. RESULTS: We examined 14 patients (9 women, 5 men, mean age 58.4 years) with previously implanted SCS systems for chronic neuropathic pain, using QST (7 tests, 13 parameters).The QST raw data showed a statistically significant improved vibration sensation (A-Beta) (P = 0.019) and lower mechanical pain threshold (A-Delta) (P = 0,031) when testing BurstDR in comparison to tonic SCS. We found a significant improvement in the vibration sensation and also A-Beta fiber function during BurstDR when we used the Z-value analysis (P = 0.023). With regard to Z-values, BurstDR seemed to be superior regarding the normalization tendency of the A-Delta fiber function in the mechanical pain threshold (P = 0.082), and tonic SCS seemed superior regarding heat detection threshold (C) and cold pain threshold (C and A-Delta) (P = 0.093). LIMITATIONS: The study is limited by its small number of cases. CONCLUSIONS: In this study, it could be shown that, in some QST parameters and tested fiber functions, normalization tendencies were recognizable by using BurstDR or tonic SCS. However, BurstDR SCS seemed to be superior to tonic stimulation in this regard.

Laser-evoked potentials recover gradually when using dorsal root ganglion stimulation, and this influences nociceptive pathways in neuropathic pain patients.

OBJECTIVE: Dorsal root ganglion stimulation (DRGS) is able to relieve chronic neuropathic pain. There seems evidence that DRGS might achieve this by gradually influencing pain pathways. We used laser-evoked potentials (LEP) to verify our hypothesis that the recovery of the LEP may reflect DRGS-induced changes within the nociceptive system. METHODS: Nine patients (mean age 56.8 years, range 36-77 years, two females) diagnosed with chronic neuropathic pain in the knee or groin were enrolled in the study. We measured each patient's LEP at the painful limb and contralateral control limb on the first, fourth, and seventh day after implantation of the DRGS system. We used the numeric rating scale (NRS) for the simultaneous pain assessment. RESULTS: The LEP amplitude of the N2-P2 complex showed a significant increase on day 7 when compared to day 1 (Z = -2.666, p = 0.008) and to day 4 (Z = -2.547, p = 0.011), respectively. There was no significant difference in the N2-P2 complex amplitude between ON and OFF states during DRGS. The patients' NRS significantly decreased after 1 day (p = 0.007), 4 days (p = 0.007), and 7 days (p = 0.007) when compared to the baseline. CONCLUSIONS: The results show that with DRGS, the LEP recovered gradually within 7 days in neuropathic pain patients. Therefore, reduction of the NRS in patients with chronic neuropathic pain might be due to DRGS-induced processes within the nociceptive system. These processes might indicate neuroplasticity mediated recovery of the LEP.

Neurophysiological Effects of Dorsal Root Ganglion Stimulation (DRGS) in Pain Processing at the Cortical Level.

OBJECTIVES: Dorsal root ganglion stimulation (DRGS) has been used successfully against localized neuropathic pain. Nevertheless, the effects of DRGS on pain processing, particularly at the cortical level, remain largely unknown. In this study, we investigated whether positive responses to DRGS treatment would alter patients' laser-evoked potentials (LEP). METHODS: We prospectively enrolled 12 adult patients with unilateral localized neuropathic pain in the lower limbs or inguinal region and followed them up for six months. LEPs were assessed at baseline, after one month of DRGS, and after six months of DRGS. Clinical assessment included the Numerical Rating Scale (NRS), Brief Pain Inventory (BPI), SF-36, and Beck Depression Inventory (BDI). For each patient, LEP amplitudes and latencies of the N2 and P2 components on the deafferented side were measured and compared to those of the healthy side and correlated with pain intensity, as measured with the NRS. RESULTS: At the one- and six-month follow-ups, N2-P2 amplitudes were significantly greater and NRS scores were significantly lower compared with baseline (all p's < 0.01). There was a negative correlation between LEP amplitudes and NRS scores (rs = -0.31, p < 0.10). CONCLUSIONS: DRGS is able to restore LEPs to normal values in patients with localized neuropathic pain, and LEP alterations are correlated with clinical response in terms of pain intensity.

Dorsal Root Ganglion Stimulation Used for the Treatment of Chronic Neuropathic Pain in the Groin: A Single-Center Study With Long-Term Prospective Results in 34 Cases.

OBJECTIVE: Chronic neuropathic pain in the groin is a severe condition and difficult to treat. Dorsal root ganglion stimulation (DRGS) covers discrete painful areas precisely with its stimulation power in comparison to spinal cord stimulation (SCS). It was our hypothesis that DRGS provides a long-term relief of chronic groin pain over a period of more than three years. MATERIALS AND METHODS: Patients (age >18 years) with chronic neuropathic groin pain were prospectively examined. After a successful test-trial (duration of 3-10 days, pain decrease >50%) a permanent generator was implanted. The patients were re-examined after three months, then after one year, two, and three years. We used the Visual Analogue Scale (VAS), the Pain Disability Index (PDI), the Pain Catastrophizing Scale (PCS), the Brief Pain Inventory (BPI), and the Beck Depression Inventory (BDI) for the assessment. RESULTS: We included 34 consecutive patients (13 female, 21 male, mean age 50.4 years, range of age 24-84 years, 30/34 trial to permanent conversion) during the time period from 2012 until 2016. Thirty patients had a successful test-trial and a generator was subsequently implanted. Results after three years: the preoperative VAS dropped from Mdn = 8 to Mdn = 4.5 (p = 0.001). The PDI decreased from Mdn = 48 to Mdn = 23 (p = 0.004). The PCS changed from Mdn = 31 to Mdn = 16 (p = 0.006). The BPI dropped from Mdn = 76 to Mdn = 30 (p = 0.003). The BDI decreased from Mdn = 17 to Mdn = 7 (p = 0.010). Five patients showed complications (16.7%). CONCLUSION: In this study, DRGS proved an efficient long-term method for the treatment of chronic neuropathic groin pain and we strongly recommend its use.

Lumbar spinal stenosis in elderly patients: is a unilateral microsurgical approach sufficient for decompression?

OBJECT: For the treatment of lumbar spinal stenosis, less invasive procedures, which preserve maximal bony and ligamentous structures, have been recommended to reduce associated morbidity. The authors examined the outcome after decompression of spinal stenosis in the elderly by comparing 3 different surgical approaches. Their focus was whether a unilateral microsurgical decompression provided sufficient outcomes in the elderly population. METHODS: The authors investigated 108 elderly patients (age ≥ 60 years) with lumbar spinal stenosis (mean age 71 years [range 60-93 years]) who underwent surgery between 2004 and June 2006 at the authors' institution. Three different modes of decompression were analyzed in this study: a unilateral partial hemilaminectomy, a hemilaminectomy, and a laminectomy. The outcome was assessed 12 months postoperatively using the Quebec Back Pain Disability Scale and the Hannover Functional Back Pain Questionnaire. RESULTS: The authors performed a unilateral partial hemilaminectomy in 53 patients (49%). Patients who underwent unilateral partial hemilaminectomies achieved favorable results of at least 80% as assessed using the Quebec Back Pain Disability Scale and Hannover Functional Back Pain Questionnaire. Hemilaminectomies were performed in 45 patients (41.7%), and laminectomies were performed in 10 patients (9.3%). However, there was no statistically significant difference between the various techniques regarding the postoperative results (p < 0.05). CONCLUSIONS: Laminectomies did not show any advantage when compared with unilateral transmedian approaches. A unilateral partial hemilaminectomy combined with a transmedian decompression sufficiently treated the stenosis. This method seemed advantageous in minimizing the procedure and associated morbidity in this elderly population. Further investigations with long-term results (> 5 years) are still necessary.

Recurrent spinal fistula as result of a rare combination of a perimedullary and peridural spinal fistula: case report.

OBJECTIVES: We report on a patient with the combination of a peridural and a perimedullary spinal fistula, which manifested consecutively. The clinical course and diagnostic steps reveal important observations helpful in the management of this pathology. CASE PRESENTATION: A 61-year-old male patient presented with a six-month history of progressive weakness of the lower limbs. Magnetic resonance imaging revealed edema and dilated spinal veins of the lower thoracic spinal cord. Spinal angiography confirmed the diagnosis of spinal dural fistula at level T9 on the left. The patient underwent surgery and the fistula was surgically excised. Two months after initial improvement, the clinical symptoms of lower limb weakness recurred. On re-angiography a spinal perimedullary fistula was found at level T7 that was not apparent on the previous angiogram and on the postoperative control angiogram. The patient underwent surgery again, and the second fistula was also excised. The clinical symptoms subsequently improved. CONCLUSION: The interesting point in this case was the rare combination of a peridural and a perimedullary spinal fistula. They presented consecutively and could not be identified simultaneously on the first angiogram. Only after closure of the first fistula did the second become apparent. We believe that this may be a result of a postoperative pressure change in the venous system of the cord. After closure of the first fistula, the arterio-venous (AV) shunt of the second fistula developed gradually. The possibility of a second fistula should be considered in the presence of persistent edema of the cord on magnetic resonance imaging (MRI) and subsequent clinical deterioration.