Phenol block of peripheral nerve conduction: Titrating for optimum effect

Phenol neurolysis in people with spinal cord injury: a descriptive study

STUDY DESIGN

Descriptive study.

OBJECTIVES

The study's main objective was to describe the common targets of phenol neurolysis and review the safety and efficacy of the dose used for this spasticity management procedure in people with spinal cord injury (SCI).

SETTING

An acute rehabilitation hospital.

METHODS

Data from people with SCI who underwent phenol neurolysis procedures for spasticity management between April 2017 and August 2018 were included in this study. We collected demographics and phenol neurolysis procedure-related information.

RESULTS

A total of 66 people with SCI and spasticity underwent phenol neurolysis of 303 nerves over 102 encounters. During these encounters, 97% of procedures were performed using both electrical stimulation and ultrasound guidance. The median (IQR) total volume of 6% aqueous phenol used per encounter was 4.0 (2.0-6.0) ml with a median (IQR) of 1.5 (1.0-2.3) ml per nerve. The most frequent target was the obturator nerve (33%), followed by the pectoral nerves (23%). Immediate post-phenol neurolysis improvement or reduction in spasticity was reported for 92% of all documented encounters. There was no documentation of any post-procedure-related adverse events in this cohort during this specified time frame.

CONCLUSIONS

Our findings suggest that phenol neurolysis can be safely used to manage spasticity in people with SCI under combined electrical stimulation and ultrasound guidance. Further research is required to assess the procedure's safety, efficacy, and cost-effectiveness on patient-reported outcomes compared to other spasticity interventions.

Loss of direct adrenergic innervation after peripheral nerve injury causes lymph node expansion through IFN-γ

Peripheral nerve injury can cause debilitating disease and immune cell-mediated destruction of the affected nerve. While the focus has been on the nerve-regenerative response, the effect of loss of innervation on lymph node function is unclear. Here, we show that the popliteal lymph node (popLN) receives direct neural input from the sciatic nerve and that sciatic denervation causes lymph node expansion. Loss of sympathetic, adrenergic tone induces the expression of IFN-γ in LN CD8 T cells, which is responsible for LN expansion. Surgery-induced IFN-γ expression and expansion can be rescued by β2 adrenergic receptor agonists but not sensory nerve agonists. These data demonstrate the mechanisms governing the pro-inflammatory effect of loss of direct adrenergic input on lymph node function.

Palliative Nerve Block for Penile Calciphylaxis: A Case Report on Ultrasound-Guided Phenol Neurolysis

A 78-year-old man with uncontrolled diabetes, heart failure, and hemodialysis-dependent end-stage renal disease presented with intractable penile pain secondary to calciphylaxis and necrosis of his glans penis. Given pain refractory to pharmacologic management and refusal of surgery, treatment entailed an ultrasound-guided dorsal penile nerve block with 5 mL of aqueous 4% phenol bilaterally. The patient reported immediate relief and died pain-free 3 months later. While phenol nerve blocks are increasingly uncommon due to local tissue toxicity, the precision of ultrasound leverages phenol's denaturing and axonal demyelinating properties to facilitate long-term targeted neurolysis to palliate chronic nonmalignant pain.

The Time Course of Onset and Peak Effects of Phenol Neurolysis

OBJECTIVE

The aim of this study was to explore the time course of onset and peak effects of phenol neurolysis.

DESIGN

This is a retrospective chart review. Eleven patients with elbow flexor spasticity after brain injury were enrolled. The resting angle of the elbow joint was measured before and after the injection and up to 6 wks of follow-up.

RESULTS

Phenol injection was performed to 13 musculocutaneous nerves under ultrasound and electrical stimulation guidance. The resting elbow angles were 84.4° ± 25.8° (before injection), 116.6° ± 20.9° (immediately after injection), 121.2° ± 21.4° (2 hrs after injection), 127.2° ± 19.7° (24 hrs after injection), 145.4° ± 11.8° (7 days after injection), 145.5° ± 10.4° (14 days after injection), and 150.3° ± 12.2° (6 wks after injection; N = 7). The mean resting angle was statistically different among the time points from preinjection to 14 days after (F2.625, 31.505 = 36.805, P < 0.01). Post hoc tests revealed that significant improvements existed immediately after and 7 days after the injection (P < 0.01 for both). The effects seemed to reach its peak in 7 days. The effect sizes immediately and 7 days after the injection were 1.37 and 3.04, respectively. The immediate effect accounted for approximately 60% of the maximal effect.

CONCLUSIONS

Phenol neurolysis has an immediate effect on spasticity reduction and reaches its peak effect around 1 wk after injection.

Liposomal Bupivacaine (Bupigel) Demonstrates Minimal Local Nerve Toxicity in a Rabbit Functional Model

We previously reported the development of a novel formulation of an ultra-long-acting local anesthetic based on bupivacaine encapsulated in large multivesicular liposomes (Bupisomes) embedded in hydrogel. This formulation (Bupigel) prolonged bupivacaine release from the formulation in dissolution-like studies in vitro and analgesia in vivo in mouse, rat, and pig models. In this study we assessed Bupigel neurotoxicity on rabbit sciatic nerve using histopathology and electrophysiologic testing. Sciatic nerves of both hind limbs were injected dropwise with different formulations. Nerve conduction studies and needle electromyography two weeks after perineural administration showed signs of neural damage after injection of free lidocaine and bupivacaine, while there was no sign of neural damage after injection with saline, demonstrating the validity of the method. This test also did not show evidence of motor or sensory nerve damage after injection with liposomal bupivacaine at a dose 10-times higher than free bupivacaine. Histologically, signs of neural damage could be observed with lidocaine. Nerves injected with Bupigel showed mild signs of inflammation and small residues of hydrogel in granulomas, indicating a long residence time of the hydrogel at the site of injection, but no histopathological signs of nerve damage. This demonstrated that early signs of neural damage were detected electrophysiologically, showing the usefulness and sensitivity of electrodiagnostic testing in detection of neural damage from new formulations.

Photochemical origin of reactive radicals and halogenated organic substances in natural waters: A review

Halogenated organic compounds, also termed organohalogens, were initially regarded to be of almost exclusively anthropogenic origin. However, recent research has demonstrated that photochemical reactions are important abiotic sources of organohalogen compounds in sunlit surface waters. Halide ions (X^-, X represents Cl, Br and I) are common anions in natural waters and might be oxidized by reactive species originated from photochemistry of dissolved organic matter (DOM) or inorganic photoactive species. The resulting reactive halogen species may react with organic substances with diverse bimolecular reaction rate constants, depending on the complexity and structure of organic substances. Therefore, the chemical mechanism of halogenation remains challenging to be fully elucidated. To better understand the trends in the existing data and to identify the knowledge gaps that may merit further investigation, this review gives an integrative summary on the sources of reactive oxygen species (ROS) and halogen radicals (X/X₂^-). Photochemical halogenation of phenolic compounds and formation of methyl halide and brominated organic pollutants are highlighted. By evaluating existing literature and identifying some uncertainties, this review emphasizes the environmental significance of sunlight-driven halogenation and proposes further research directions on mechanistic investigation and rational experimental design close to natural systems.

Peripheral nerve regeneration and intraneural revascularization

Peripheral nerves are particularly vulnerable to injuries and are involved in numerous pathologies for which specific treatments are lacking. This review summarizes the pathophysiological features of the most common traumatic nerve injury in humans and the different animal models used in nerve regeneration studies. The current knowledge concerning Wallerian degeneration and nerve regrowth is then described. Finally, the involvement of intraneural vascularization in these processes is addressed. As intraneural vascularization has been poorly studied, histological experiments were carried out from rat sciatic nerves damaged by a glycerol injection. The results, taken together with the data from literature, suggest that revascularization plays an important role in peripheral nerve regeneration and must therefore be studied more carefully.

Mechanisms and treatment of painful neuromas

A painful neuroma is a common complication of a peripheral nerve injury or amputation, and it can cause tremendous pain that is resistant to most analgesics. Furthermore, painful neuromas have a high postoperative recurrence rate. Painful neuromas are often accompanied by functional disorders, drastically reducing the patient’s quality of life. Several pathophysiological mechanisms have been proposed to explain this type of neuropathic pain, including peripheral and central sensitisation and the involvement of nerve growth factor, α-smooth muscle actin, the cannabinoid CB2 receptor and structural changes in neuroma fibres. Nevertheless, the mechanisms of neuroma-associated pain are not fully understood, contributing to the challenge of managing patients with painful neuromas. There are several effective treatment methods, although none are universally accepted. This review summarises the common mechanisms and treatments of painful neuromas, attempting to link the mechanisms and treatments. We hope to provide useful guidelines for choosing the appropriate treatment for the management of painful neuromas.

Anatomical study of the nerve regeneration after selective neurectomy in the rabbit: clinical application for esthetic calf reduction

The purposes of this study were therefore to characterize the degeneration and regeneration of nerves to the calf muscles after selective neurectomy, both macroscopically and microscopically, and to determine the incidence of such regeneration in a rabbit model. Seventy four New Zealand white rabbits were used. Selective neurectomy to the triceps surae muscles was performed, and the muscles were subsequently harvested and weighed 1-4 months postneurectomy. The gastrocnemius muscles were stained with Sihler's solution to enable the macroscopic observation of any nerve regeneration that may have occurred subsequent to neurectomy. The change in triceps surae muscle weight was measured along the time course of the experiment. After neurectomy, nerve degeneration was followed by regeneration in all cases. The weight of the triceps surae muscle decreased dramatically between completion of the neurectomy and 1 month postneurectomy, but increased thereafter. The nerve branches were weakly stained with Sihler's solution until 2 months postneurectomy, and then strongly stained after 3 months. The number of myelinated axons was decreased at 2 month after neurectomy compared to nonneurectomized controls, but then gradually increased thereafter. Although there are currently no reports on the incidence of recovery after calf reduction, it may be a very common occurrence in the clinical field based on our findings. The findings of this study provide fundamental anatomical and surgical information to aid planning and practice in calf-reduction surgery.

Painful neuromas

OBJECTIVES

To perform a topical review of the published literature on painful neuromas.

METHODS

A MEDLINE search was performed using the MESH terms "neuroma", "pain", "diagnosis", and "treatment" for all dates.

RESULTS

Acoustic neuromas and intraabdominal neuromas were excluded from a total of 7616 articles. The reference lists from these articles were further reviewed to obtain other relevant articles.

DISCUSSION

Neuromas develop as part of a normal reparative process following peripheral nerve injury. Painful neuromas can induce intense pain resulting in immense suffering and disability. MRI aids the diagnosis, but, ultrasound imaging allows cost effective accurate diagnosis and localization of neuromas by demonstrating their direct contiguity with the nerve of origin. Management options for painful neuromas include pharmacotherapy, prosthetic adjustments, steroid injection, chemical neurolysis, cryoablation, and radiofrequency ablation. Ultrasound imaging guidance has improved the success in localizing and targeting the neuromas. This review discusses the patho-physiology and accumulated evidence for various therapies and the current percutaneous interventional management options for painful neuromas.

A MILD ACUTE COMPRESSION INDUCES NEURAPRAXIA IN RAT SCIATIC NERVE

The pressure that induces neurapraxia in rat remains unrevealed. To determine the appropriate force to induce neurapraxia, two types of clips were applied to the sciatic nerve and were evaluated with functional, electrophysiological, and histological examinations. With a compression of 60 g/mm2, walking track analysis showed complete sciatic nerve paralysis one day postoperatively, but became normal in 14 days. Electrophysiologically, complete conduction block occurred one day post operatively, whereas the motor conduction velocity (MCV) below the compression site remained normal. Histologically, only limited signs of Wallerian degeneration were seen. The model in this study exhibited the features of neurapraxia.

The validity and reliability of the motor point detection system: a preliminary investigation of motor points of the triceps surae muscles

OBJECTIVE

To investigate the validity and reliability of the motor point detection system in cadavers and healthy young adults.

DESIGN

Correlation statistics.

SETTING

University research laboratory.

PARTICIPANTS

Sixty-two lower limbs of 31 healthy young adults (mean age, 22.3+/-1.8) and 10 size-matched lower limbs from cadavers were used.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The validity of the motor point detection system's motor point measure was determined by comparing the motor point locations of the lower-leg muscles obtained from the motor point detection system with the established anatomic motor point locations from our previous cadaveric dissection study. The anatomic motor points were determined by tracing the terminal motor nerve branches on soleus, medial, and lateral gastrocnemius muscles through the dissection of adult cadavers. The test-retest reliability was determined by repeatedly measuring the locations of motor points in healthy young adults on 2 separate occasions, approximately 24 hours apart. The intraclass correlation coefficient (ICC) was computed to determine correlation, and an independent t test was used to determine the difference between the demographic and clinical variables at the significance level (P<.05).

RESULTS

Correlation analysis revealed relatively high validity between the motor point detection system and cadaver-dissected motor point location measurements (ICC(2,1)=.71-.92, P<.05). The test-retest reliability showed excellent correlation between the repeated measures (range, ICC(1,2)=.90-.95 at P<.05).

CONCLUSIONS

Our results showed that the motor point detection system was accurate and consistent in the measurement of motor point locations of the lower-leg muscles. This system can be considered as an alternative device to localize motor points in clinical settings. Our motor point detection system warrants further investigation in pathologic population.

Adductor release and chemodenervation in children with cerebral palsy: a pilot study in 16 children

PURPOSE

A pilot study with short-term outcomes of a combined surgical and medical intervention for management of generalized lower limb spasticity, hip displacement and contractures of adductors in children with bilateral spastic cerebral palsy.

METHODS

A prospective cohort study of 16 children (9 boys and 7 girls) aged 2-6 years with bilateral spastic cerebral palsy was performed. At entry, 5 were classified as level III and 11 as level IV, according to the Gross Motor Function Classification System (GMFCS). The intervention consisted of surgical lengthening of adductor longus and gracilis combined with the phenolization of the anterior branch of the obturator nerve, using 1 ml of 6% phenol, applied under direct vision at the time of lengthening of adductor longus. The hamstring and calf muscles were each injected with Botulinum neurotoxin A at a dose of 4 U/kg/muscle. Serial clinical (hip, knee, ankle joint range of motion), radiographic (migration percentage) and functional data-taken from a functional mobility scale (FMS) or GMFCS-were collected at 3, 6, 12 and 24 months post-operatively.

RESULTS

There was a significant increase in hip abduction, knee extension (popliteal angle) and ankle dorsiflexion, maintained for 24 months; mean hip migration percentage decreased from 29 to 21% (P < 0.001). Using a validated mobility scale, significant improvements were noted in gross motor function. There were no complications related to the intervention.

CONCLUSIONS

The combined surgical-medical intervention resulted in a reduction of spastic hip subluxation and improvements in gross motor function, as determined by the FMS. The combined intervention is, thus, useful as a temporizing measure, before definitive decisions are made considering such interventions as dorsal rhizotomy, intrathecal baclofen and single-event, multilevel surgery.

Practical experience with sonographically guided phenol instillation of stump neuroma: predictors of effects, success, and outcome

OBJECTIVE

Phantom limb pain and stump pain frequently occur after limb amputation, and stump neuromas play an important role in generation of the pain. The purpose of this study was to evaluate the effects of a previously described optimized procedure for sclerosis of painful stump neuromas under real-time high-resolution sonographic guidance.

SUBJECTS AND METHODS

In this prospective study, neurosclerosis was performed on 82 patients by means of high-resolution sonographically guided injection of up to 0.8 mL of 80% phenol solution according to a standardized protocol.

RESULTS

During treatment all patients had marked improvement in terms of reduction of pain measured with a visual analog scale. Twelve (15%) of the subjects were pain free after one to three treatments, nine of the 12 achieving relief with the initial instillation. At 6-month follow-up evaluation, 52 patients assessed their present pain quantity with a simplified three-step score. Twenty (38%) of the 52 patients reported almost unnoticeable pain, and 33 (64%) reported pain equal to the minimum reached during therapy. In 18 (35%) of the 52 patients, the incidence of painful periods had markedly decreased. The neurosclerosis procedure had a low complication rate (5% rate of minor complications, 1.3% rate of major complications).

CONCLUSION

The high-resolution sonographically guided neurosclerosis procedure had a significantly better outcome than other documented treatments. Sonographically guided neurosclerosis should be included in the management of chronic phantom limb and stump pain.