Pain Responses on Stimulation of the Lumbar Sympathetic Chain Under Local Anesthesia

Photobiomodulation of the dorsal root ganglion for the treatment of low back pain: A pilot study

BACKGROUND AND OBJECTIVE

Chronic low back pain is a worldwide public health issue with high socioeconomic impact. The aim of this study was to determine the efficacy of laser irradiation of the dorsal root ganglion of the second lumbar spinal nerve for chronic axial low back pain compared to lidocaine injection and radiofrequency treatment.

STUDY DESIGN/MATERIALS AND METHODS

Twenty-eight patients were randomly divided into three treatment groups: lidocaine injection, radiofrequency, or laser. The second intervertebral foramen between the second and third lumbar vertebrae was accessed by percutaneous needle puncture bilaterally, guided by fluoroscopy. In the local anesthetic group, injection of 1 ml lidocaine without epinephrine was applied through a 20-gauge (G20) Quincke tip spinal needle inserted in the second lumbar intervertebral foramen. In the radiofrequency group, the probe (150 mm long with a 5 mm active tip) was directed through a G20 needle placed in the second lumbar intervertebral foramen and neuromodulation was done with a radiofrequency of Cosman G4® in pulses of 20 ms with wash-out period of 480 ms, for 300 seconds at 42°C. A single treatment was used. In the laser treatment group, a continuous wave, 808 nm wavelength diode laser (Photon Lase III® DCM, Brazil), with an output power of 100 mW was used for a single treatment. An 18 gauge needle was placed in the second lumbar intervertebral foramen guided by fluoroscopy. Light was delivered through a 600 µm optical fiber placed in the G18 needle. The tip of the fiber extended 5 mm beyond the tip of the needle in the second lumbar intervertebral foramen. The beam spot size was 0.003 cm(2) , irradiance = 35W/cm(2) , exposure time = 84 seconds, energy density = 2800J/cm(2) , total energy was 8.4 J. The low back pain score was assessed by the visual analog scale (VAS) and Pain Relief Scale (PRS) pre, post procedure and in 1 month follow up. Temperature was measured using a digital thermometer.

RESULTS

All patients in the local anesthetic and laser treatment groups reported a pain reduction of at least 50% immediately post-procedure and 10 out of 11 patients in the radiofrequency group reported a pain reduction of at least 50%. At 1 month post-treatment, the laser treatment group had the greatest number of patients who reported more than 50% pain relief based on PRS (7 out of 10 patients) while only 2 out of 7 patients and 3 out of 11 patients in the lidocaine and radiofrequency treatment groups respectively reported more than a 50% pain relief.

CONCLUSION

Laser irradiation caused an immediate decrease in low back pain post-procedure similar to pain reduction caused by lidocaine injection. Both lidocaine injection and laser irradiation were more effective than radiofrequency treatment for immediate and longer term (1 month post-treatment) chronic back pain. Lasers Surg. Med. 48:653-659, 2016. © 2016 Wiley Periodicals, Inc.

Use of Temporary Implantable Biomaterials to Reduce Leg Pain and Back Pain in Patients with Sciatica and Lumbar Disc Herniation

The principle etiology of leg pain (sciatica) from lumbar disc herniation is mechanical compression of the nerve root. Sciatica is reduced by decompression of the herniated disc, i.e., removing mechanical compression of the nerve root. Decompression surgery typically reduces sciatica more than lumbar back pain (LBP). Decompression surgery reduces mechanical compression of the nerve root. However, decompression surgery does not directly reduce sensitization of the sensory nerves in the epidural space and disc. In addition, sensory nerves in the annulus fibrosus and epidural space are not protected from topical interaction with pain mediators induced by decompression surgery. The secondary etiology of sciatica from lumbar disc herniation is sensitization of the nerve root. Sensitization of the nerve root results from a) mechanical compression, b) exposure to cellular pain mediators, and/or c) exposure to biochemical pain mediators. Although decompression surgery reduces nerve root compression, sensory nerve sensitization often persists. These observations are consistent with continued exposure of tissue in the epidural space, including the nerve root, to increased cellular and biochemical pain mediators following surgery. A potential contributor to lumbar back pain (LBP) is stimulation of sensory nerves in the annulus fibrosus by a) cellular pain mediators and/or b) biochemical pain mediators that accompany annular tears or disruption. Sensory fibers located in the outer one-third of the annulus fibrosus increase in number and depth as a result of disc herniation. The nucleus pulposus is comprised of material that can produce an autoimmune stimulation of the sensory nerves located in the annulus and epidural space leading to LBP. The sensory nerves of the annulus fibrosus and epidural space may be sensitized by topical exposure to cellular and biochemical pain mediators induced by lumbar surgery. Annulotomy or annular rupture allows the nucleus pulposus topical access to sensory nerve fibers, thereby leading to LBP. Coverage of the annulus and adjacent structures in the epidural space by absorbable viscoelastic gels appears to reduce LBP following surgery by protecting sensory fibers from cellular and biochemical pain mediators.

The anatomic and physiologic basis of local, referred and radiating lumbosacral pain syndromes related to disease of the spine

Conscious perception and unconscious effects originating from the vertebral column and its neural structures, although complex, have definite pathways represented in a network of peripheral and central nervous system (CNS) ramifications. These neural relationships consequently result in superimposed focal and diffuse, local and remote conscious perceptions and unconscious effects. Any one or combination of somatic and autonomic signs and symptoms may potentially be observed in a particular patient. This variety and inconsistency may mislead or confuse both the patient and the physician. A clear understanding of the basic anatomic and physiologic concepts underlying this complexity should accompany clinical considerations of the potential significance of spondylogenic and neurogenic syndromes in any disease process affecting the spine.

Dorsal root entry zone microcoagulation for spinal cord injury-related central pain: operative intramedullary electrophysiological guidance and clinical outcome

OBJECT

Surgically created lesions of the spinal cord dorsal root entry zone (DREZ) to relieve central pain after spinal cord injury (SCI) have historically resulted in modest outcomes. A review of the literature indicates that fair to good relief of pain is achieved in approximately 50% of patients when an empirical procedure is performed. This study was undertaken to determine if intramedullary electrical guidance in DREZ lesioning could improve outcomes in patients with SCI-induced central pain. Additionally, electrical data were used to determine if the spinal cord could be somatotopically mapped with regard to this pain of central origin.

METHODS

Forty-one patients with traumatic SCI and intractable central pain underwent DREZ lesioning in which intramedullary electrical guidance was conducted. In nine patients, recording of DREZ-related spontaneous electrical hyperactivity guided the lesioning process. In 32 patients, recording of DREZ-induced evoked electrical hyperactivity during transcutaneous C-fiber stimulation (TCS) additionally guided lesioning. The follow-up period ranged from 1 to 7 years. The analyzed electrical data allowed for somatotopic mapping of the spinal cord.

CONCLUSIONS

Intramedullary electrical guidance of DREZ lesioning substantially improves pain outcomes in patients with traumatic SCI-induced central pain, compared with an empiric technique. The best outcome occurs when DREZ-related spontaneous electrical hyperactivity and evoked hyperactivity during TCS are both used to guide the DREZ lesioning procedure. With such guidance, 100% relief of pain was achieved in 84% of patients and 50 to 100% relief of pain in 88%. Somatotopic mapping of the electrical data led to a proposed pain mechanism for below-level pain, implicating the sympathetic nervous system.

Post-sympathectomy neuralgia: hypotheses on peripheral and central neuronal mechanisms

Post-sympathectomy neuralgia is proposed here to be a complex neuropathic and central deafferentation/reafferentation syndrome dependent on: (a) the transection, during sympathectomy, of paraspinal somatic and visceral afferent axons within the sympathetic trunk; (b) the subsequent cell death of many of the axotomized afferent neurons, resulting in central deafferentation; and (c) the persistent sensitization of spinal nociceptive neurons by painful conditions present prior to sympathectomy. Viscerosomatic convergence, collateral sprouting of afferents, and mechanisms associated with sympathetically maintained pain are all proposed to be important to the development of the syndrome.

Sympathetic activation of cat spinal neurons responsive to noxious stimulation of deep tissues in the low back

Prior findings from diverse studies have indicated that activity in axons located in the lumbar sympathetic chains contributes to the activation of spinal pain pathways and to low back pain; these studies have utilized sympathetic blocks in patients, electrical stimulation of the chain in conscious humans, and neuroanatomical mapping of afferent fiber projections. In the present study, dorsal horn neurons receiving nociceptor input from lumbar paraspinal tissues were tested for activation by electrical stimulation of the lumbar sympathetic chain in anesthetized cats. Of 83 neurons tested, 70% were responsive to sympathetic trunk stimulation. Excitatory responses, observed in both nociceptive specific and wide-dynamic-range neurons, were differentiable into two classes: non-entrained and entrained responses. Non-entrained responses were attenuated or blocked by systemic administration of the alpha-adrenergic antagonist phentolamine and are thought to result from sympathetic efferent activation of primary afferents in the units' receptive fields. Entrained responses were unaffected by phentolamine and are thought to result from electrical activation of somatic and/or visceral afferent fibers ascending through the sympathetic trunk into the dorsal horn. These findings from nocireceptive neurons serving lumbar paraspinal tissues suggest that low back pain may be exacerbated by activity in both efferent and afferent fibers located in the lumbar sympathetic chain, the efferent actions being mediated indirectly through sympathetic-sensory interactions in somatic and/or visceral tissues.

Psychophysical correlates of phantom limb experience

Phantom limb phenomena were correlated with psychophysiological measures of peripheral sympathetic nervous system activity measured at the amputation stump and contralateral limb. Amputees were assigned to one of three groups depending on whether they reported phantom limb pain, non-painful phantom limb sensations, or no phantom limb at all. Skin conductance and skin temperature were recorded continuously during two 30 minute sessions while subjects continuously monitored and rated the intensity of any phantom limb sensation or pain they experienced. The results from both sessions showed that mean skin temperature was significantly lower at the stump than the contralateral limb in the groups with phantom limb pain and non-painful phantom limb sensations, but not among subjects with no phantom limb at all. In addition, stump skin conductance responses correlated significantly with the intensity of non-painful phantom limb paresthesiae but not other qualities of sensation or pain. Between-limb measures of pressure sensitivity were not significantly different in any group. The results suggest that the presence of a phantom limb, whether painful or painless, is related to the sympathetic-efferent outflow of cutaneous vasoconstrictor fibres in the stump and stump neuromas. The hypothesis of a sympathetic-efferent somatic-afferent mechanism involving both sudomotor and vasoconstrictor fibres is proposed to explain the relationship between stump skin conductance responses and non-painful phantom limb paresthesiae. It is suggested that increases in the intensity of phantom limb paresthesiae follow bursts of sympathetic activity due to neurotransmitter release onto apposing sprouts of large diameter primary afferents located in stump neuromas, and decreases correspond to periods of relative sympathetic inactivity. The results of the study agree with recent suggestions that phantom limb pain is not a unitary syndrome, but a symptom class with each class subserved by different aetiological mechanisms.

Limb pain in migraine and cluster headache

Upper limb pain occurred in close temporal association with attacks of migraine, cluster headache and cluster-migraine in 22 cases. Seven had also lower limb pain. Limb pain was usually ipsilateral to the headache but could alternate sides and behaved like other accepted migraine accompaniments. It was always ipsilateral to the associated paraesthesiae/numbness (9 cases) and weakness (6 cases). The distribution and restricted localisations of limb pain were similar to those of the sensory symptoms and could not be accounted for by primary dysfunction of the peripheral or autonomic nervous systems. A central origin for limb pain is postulated. A temporary dysfunction in the somatosensory cortex, and/or its thalamic connections, during migraine or cluster headache attacks, might mediate such pain in a number of patients.