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.

Comparing Electrical Stimulation With and Without Ultrasound Guidance for Phenol Neurolysis to the Musculocutaneous Nerve.

BACKGROUND: Ultrasound guidance is increasingly being used for neurolytic procedures that have traditionally been done with electrical stimulation (e-stim) guidance alone. Ultrasound visualization with e-stim-guided neurolysis can potentially allow adjustments in injection protocols that will reduce the volume of neurolytic agent needed to achieve clinical improvement. OBJECTIVE: This study compared e-stim only to e-stim with ultrasound guidance in phenol neurolysis of the musculocutaneous nerve (MCN) for elbow flexor spasticity. We also evaluated the ultrasound appearance of the MCN in this population. DESIGN: Retrospective review. SETTING: University hospital outpatient clinic. PARTICIPANTS: Adults (N = 167) receiving phenol neurolysis to the MCN for treatment of elbow flexor spasticity between 1997 and 2014 and adult control subjects. METHODS: For each phenol injection of the MCN, the method of guidance, volume of phenol injected, technical success, improved range of motion at the elbow postinjection, adverse effects, reason for termination of injections, and details of concomitant botulinum toxin injection were recorded. The ultrasound appearance of the MCN, including nerve cross-sectional area and shape, were recorded and compared between groups. MAIN OUTCOME MEASURES: The volume of phenol injected and MCN cross-sectional area and shape as demonstrated by ultrasound. RESULTS: The addition of ultrasound to e-stim-guided phenol neurolysis was associated with lower doses of phenol when compared to e-stim guidance alone (2.31 mL versus 3.69 mL, P < .001). With subsequent injections, the dose of phenol increased with e-stim guidance (P < .001), but not with e-stim and ultrasound guidance (P = .95). Both methods of guidance had high technical success, improved ROM at elbow postinjection, and low rates of adverse events. In comparing the ultrasound appearance of the MCN in patients with spasticity to that of normal controls, there was no difference in the cross-sectional area of the nerve, but there was more variability in shape. CONCLUSIONS: Combined e-stim and ultrasound guidance during phenol neurolysis to the MCN allows a smaller volume of phenol to be used for equal effect, both at initial and repeat injection. The MCN shape was more variable in individuals with spasticity; this should be recognized so as to successfully locate the nerve to perform neurolysis. LEVEL OF EVIDENCE: IV.

Ciliary neurotrophic factor promotes motor reinnervation of the musculocutaneous nerve in an experimental model of end-to-side neurorrhaphy.

BACKGROUND: It is difficult to repair nerve if proximal stump is unavailable or autogenous nerve grafts are insufficient for reconstructing extensive nerve damage. Therefore, alternative methods have been developed, including lateral anastomosis based on axons' ability to send out collateral sprouts into denervated nerve. The different capacity of a sensory or motor axon to send a sprout is controversial and may be controlled by cytokines and/or neurotrophic factors like ciliary neurotrophic factor (CNTF). The aim of the present study was to quantitatively assess collateral sprouts sent out by intact motor and sensory axons in the end-to-side neurorrhaphy model following intrathecal administration of CNTF in comparison with phosphate buffered saline (vehiculum) and Cerebrolysin. The distal stump of rat transected musculocutaneous nerve (MCN) was attached in an end-to-side fashion with ulnar nerve. CNTF, Cerebrolysin and vehiculum were administered intrathecally for 2 weeks, and all animals were allowed to survive for 2 months from operation. Numbers of spinal motor and dorsal root ganglia neurons were estimated following their retrograde labeling by Fluoro-Ruby and Fluoro-Emerald applied to ulnar and musculocutaneous nerve, respectively. Reinnervation of biceps brachii muscles was assessed by electromyography, behavioral test, and diameter and myelin sheath thickness of regenerated axons. RESULTS: Vehiculum or Cerebrolysin administration resulted in significantly higher numbers of myelinated axons regenerated into the MCN stumps compared with CNTF treatment. By contrast, the mean diameter of the myelinated axons and their myelin sheath thickness in the cases of Cerebrolysin- or CNTF-treated animals were larger than were those for rats treated with vehiculum. CNTF treatment significantly increased the percentage of motoneurons contributing to reinnervation of the MCN stumps (to 17.1%) when compared with vehiculum or Cerebrolysin treatments (at 9.9 or 9.6%, respectively). Reduced numbers of myelinated axons and simultaneously increased numbers of motoneurons contributing to reinnervation of the MCN improved functional reinnervation of the biceps brachii muscle after CNTF treatment. CONCLUSION: The present experimental study confirms end-to-side neurorrhaphy as an alternative method for reconstructing severed peripheral nerves. CNTF promotes motor reinnervation of the MCN stump after its end-to-side neurorrhaphy with ulnar nerve and improves functional recovery of the biceps brachii muscle.

Evaluation of a midhumeral block of the radial, ulnar, musculocutaneous and median (RUMM block) nerves for analgesia of the distal aspect of the thoracic limb in dogs.

OBJECTIVE: To evaluate a technique for midhumeral peripheral nerve blockade in the dog. STUDY DESIGN: Cadaveric technique development; in vivo placebo-controlled, prospective crossover study. ANIMALS: Canine cadavers (n=38) and 8 clinically healthy, adult hound dogs. METHODS: A technique for peripheral block of the radial, ulnar, musculocutaneous, and median nerves (RUMM block) was evaluated using cadaver limbs. Eight purpose-bred, research dogs were anesthetized; a RUMM block was performed on each thoracic limb. One limb from each dog randomly received 0.5% bupivacaine and the opposite limb was assigned to receive sterile saline solution as a control. After recovery from anesthesia, skin sensation at selected dermatomes was evaluated for 24 hours using a mechanical stimulus. Weight-bearing, conscious proprioception, and withdrawal reflex were also evaluated. One month after initial testing, each dog was reanesthetized and each limb received the opposite treatment. RESULTS: Sensory thresholds were significantly increased over baseline measurements when compared with control limbs for all nerves. Complete sensory block was achieved in radial (15/16), ulnar (3/16), musculocutaneous (8/16), and median (11/16) nerves, using a mechanical stimulus of analgesia. Complete simultaneous block of all nerves was only obtained in 1 of 16 limbs. CONCLUSION: RUMM block resulted in desensitization of the skin in the associated dermatomes for 4-10 hours. Complete sensory block of the dermatomes supplied by the radial nerve was most consistent. CLINICAL RELEVANCE: RUMM block may be an effective technique to provide adjunctive analgesia for dogs undergoing surgery of the distal aspect of the thoracic limb.

Low-dose FK506 after contralateral C7 transfer to the musculocutaneous nerve using two different tubes: a study in rats.

The purpose of this project was to study the effect of a subimmunosuppressive dose of FK506 (0.7 mg/kg per day) on nerve regeneration along a long nerve gap (4 cm), using the contralateral C7 nerve root transfer model for musculocutaneous nerve neurotization. Two types of tubes were applied to the nerve gap: a polycaprolactone tube and a collagen tube. Twenty adult male Sprague-Dawley rats were divided into 4 groups (n = 5). A polycaprolactone was used in groups 1 and 3 and a collagen tube in groups 2 and 4. Groups 1 and 2 were daily administered a subimmunosuppressive dose of FK506. Animals were euthanized on day 30. Evaluation consisted of behavioral assessment, needle electromyography studies, biceps muscle weight measurements, and qualitative and quantitative morphometry. Groups 1 and 2 showed higher mean values for fiber counts, axon diameters, myelin thickness and myelin area in C7, better functional evaluation results, and higher biceps weight left to right ratio than groups 3 and 4. There was no evidence of reinnervation potentials, and there were no axons detectable inside the tube lumen in any of the study groups. The present study demonstrated that there was nonsignificant improvement of the functional recovery, after systemic administration of a low dose of FK506. This was attributed to 3 factors: length of nerve gap; duration of follow up; and dose of FK506. However, FK506-treated animals tended to be in a more advanced stage of nerve regeneration compared with the control groups.

Single stimulation of the posterior cord is superior to dual nerve stimulation in a coracoid block.

BACKGROUND: Both multiple injection and single posterior cord injection techniques are associated with extensive anesthesia of the upper limb after an infraclavicular coracoid block (ICB). The main objective of this study was to directly compare the efficacy of both techniques in terms of the rates of completely anesthetizing cutaneous nerves below the elbow. METHODS: Seventy patients undergoing surgery at or below the elbow were randomly assigned to receive an ICB after the elicitation of either a single radial nerve-type response (Radial group) or of two different main nerve-type responses of the upper limb, except for the radial nerve (Dual group). Forty milliliters of 1.5% mepivacaine was given in a single or a dual dose, according to group assignment. The sensory block was assessed in each of the cutaneous nerves at 10, 20 and 30 min. Block performance times and the rates of complete anesthesia below the elbow were also noted. RESULTS: Higher rates of sensory block of the radial nerve were found in the Radial group at 10, 20 and 30 min (P<0.05). The rates of sensory block of the ulnar nerve at 30 min were 97% and 75% in the Radial and in the Dual groups, respectively (P<0.05). The rate of complete anesthesia below the elbow was also higher in the Radial group at 30 min (P<0.05). CONCLUSIONS: Injection of a local anesthetic after a single stimulation of the radial nerve fibers produced more extensive anesthesia than using a dual stimulation technique under the conditions of our study.

A comparison of stimulation patterns in axillary block: part 2.

BACKGROUND AND OBJECTIVES: Radial plus musculocutaneous nerve stimulation may have a predominant role in the success of an axillary block, producing more extensive anesthesia of the upper limb than median plus musculocutaneous nerve stimulation. However, no comparison has been made with ulnar plus musculocutaneous nerve stimulation. We compared the extent of both sensory and motor block after ulnar plus musculocutaneous nerve stimulation or radial plus musculocutaneous nerve stimulation. METHODS: Sixty patients were randomly assigned to receive an axillary block using either radial plus musculocutaneous or ulnar plus musculocutaneous nerve stimulation with 40 mL plain 1.5% mepivacaine. Patients were assessed for sensory block by the pinprick method at 5 and 20 minutes. RESULTS: No statistically significant differences were found in the rates of anesthesia at 20 minutes in the cutaneous nerve distributions of the upper limb between radial plus musculocutaneous and ulnar plus musculocutaneous nerve stimulation except for the following nerves: radial (90% and 63.3%, respectively), medial cutaneous of the forearm (83.3% and 100%, respectively), and medial cutaneous of the arm (73.3% and 93.3%, respectively). Global sensory score (minimum: 0; maximum: 12 points) at 20 minutes was significantly higher after radial plus musculocutaneous than after ulnar plus musculocutaneous nerve stimulation: 12 (11-13) and 11 (10-12), respectively. The rates of median nerve blockade were 50% and 53%, respectively. CONCLUSIONS: Radial plus musculocutaneous nerve stimulation produced more extensive anesthesia of the upper limb than did ulnar plus musculocutaneous nerve stimulation. However, there is not an optimal combination of 2 responses in axillary brachial plexus block.

Lateral antebrachial cutaneous neuropathy in a windsurfer.

Lateral antebrachial cutaneous neuropathy (LACN) was diagnosed in a young woman who developed pain and paresthesias in the right forearm after a long day of windsurfing (board sailing). The symptoms resolved with conservative treatment, including cessation of windsurfing and a brief course of oral corticosteroids. There was a permanent residual cutaneous sensory deficit in the distribution of the LACN. LACN is important to recognize because the symptomatology may mimic pathology of a cervical root, the brachial plexus, and the radial and median nerves at the level of the elbow.

A review on conotoxins targeting ion channels and acetylcholine receptors of the vertebrate neuromuscular junction.

In this article we present an overview of some peptides extracted and purified from the venom of marine snails of the genus Conus. These active peptides named conotoxins can be used as research tools to target voltage-gated ion channels as well as ligand-gated receptors. Because of their relatively small size, conotoxins can be chemically synthesized and made widely available. In this review we focus on conotoxins that target voltage-sensitive sodium channels, voltage-dependent calcium channels and nicotinic acetylcholine receptors of the vertebrate neuromuscular junction. Emphasis is given on summarizing our current knowledge of their primary structure and their specific pharmacological actions at the pre- and the post-synaptic level of the neuromuscular junction. Evidence is presented for conotoxins that discriminate between pre- and post-synaptic voltage-gated sodium channels. Among these peptides, the mu-conotoxin family is well characterized by its ability to block selectively sodium channels in skeletal muscle fibres without affecting axonal and nerve terminal Na+ channels. Furthermore, new conotoxins like Conus consors toxin (CcTx) and conotoxin EVIA selectively target Na+ channels in axons and nerve terminals without affecting skeletal muscle fibres. omega-conotoxins known as highly potent and selective blockers of voltage-sensitive calcium channels have proven to be valuable in determining the roles of the various subtypes of channels involved in acetylcholine release from motor nerve endings. Finally, Conus peptides which act at muscle nicotinic acetylcholine receptors constitute the most extensive characterized family of conopeptides that exhibit sequence similarity, different structural motifs and surprising diversity in their competitive and non-competitive actions.

[1% mepivacaine and axillary block: duration of the sensory and motor blockade]. / Mépivacaïne à 1% et bloc axillaire: durée du bloc sensitif et moteur.

OBJECTIVES: To assess the duration of both sensory and motor blockade of brachial plexus with 40 mL 1% mepivacaine after axillary or midhumeral approach. STUDY DESIGN: Prospective, open, non-comparative, multicentric study. PATIENTS: One hundred and eighty patients, ASA physical class 1 and 2, scheduled for hand or forearm surgery under brachial plexus block were included. METHODS: A midhumeral or axillary brachial plexus block using a nerve stimulator was performed with 40 mL of 1% mepivacaine. Sensory blockade was tested for each cutaneous area (median, radial, ulnar, musculocutaneous and medial cutaneous nerve of the forearm) using pin-prick. Motor blockade was assessed by grip strength of the hand. Incidence and duration of analgesia, anaesthesia and motor blockade were assessed. The incidence of tourniquet pain and the time when pain occurred were determined. RESULTS: According to the nerve area tested, analgesia and anaesthesia were obtained in 98% and 85% of cases respectively; duration of anaesthesia was between 150 +/- 40 to 167 +/- 49 minutes and duration of analgesia was from 184 +/- 50 to 205 +/- 51 minutes. Duration of paralysis was 144 +/- 40 minutes and duration of paresis was 190 +/- 51 minutes. Pain occurred in three out of 138 patients at tourniquet inflation and in six patients after completion of surgery. CONCLUSIONS: Mid humeral or axillary block with 40 mL of 1% mepivacaine is highly successful and provides efficient surgical anaesthesia for various surgical procedures of intermediary duration.

Infraclavicular brachial plexus block effects on respiratory function and extent of the block.

BACKGROUND AND OBJECTIVES: Axillary block is devoid of severe respiratory complications. However, incomplete anesthesia of the upper limb is the main disadvantage of the technique. Theoretically, the more proximal infraclavicular approach would produce a more extensive block without the risk of pneumothorax. However, neither its effects on respiratory function nor a detailed characterization of the extent of neural block has been assessed. The goal of this study was to evaluate the possible changes in respiratory function and also the extent of the block after infraclavicular block. METHODS: We performed an infraclavicular block with a mixture of 40 mL 1.5% plain mepivacaine and 4 mL 8.4% sodium bicarbonate in 20 patients. Forced expiratory volumes were measured before and 15 minutes after the injection of local anesthetic, and sensory and motor block were evaluated at 10 and 20 minutes. RESULTS: We did not find significant differences from baseline in the forced expiratory volumes in any of the patients. Axillary and musculocutaneous nerve distributions had the lowest rate of sensory block at 20 minutes. CONCLUSIONS: Infraclavicular block does not produce a reduction in respiratory function.

The use of a selective axillary nerve block for outpatient hand surgery.

UNLABELLED: Although no guidelines concerning discharge criteria after axillary plexus block are available, many institutions consider recovery of motor function as a critical factor. With the midhumeral approach, the four main nerves of the upper extremity can be blocked separately using a peripheral nerve stimulator. The aim of this double-blind study was to block the radial (R) and musculocutaneous (MC) nerves with lidocaine, and the median (M) and ulnar (U) nerves with bupivacaine to recover motor function of the elbow and wrist more rapidly while maintaining long-lasting postoperative analgesia at the operative site. Patients undergoing surgery for Dupuytren's contracture were randomized into two groups in a double-blind fashion: in the control group (n = 17), each of the four nerves was infiltrated with 10 mL of a mixture of 2% lidocaine and 0.5% bupivacaine, whereas in the selective group (n = 17), the R and MC nerves were blocked with 10 mL of 2% lidocaine each and the M and U nerves were blocked with 10 mL of 0.5% bupivacaine each. Recovery of motor block was significantly faster in the selective group (231 +/- 91 vs 466 +/- 154 min). However, time to first sensation of pain was not different between groups (707 +/- 274 vs 706 +/- 291 min). In conclusion, this new approach at the midhumeral level enables the anesthesiologist to selectively administer local anesthetics on different nerves. IMPLICATIONS: In outpatients undergoing surgery for Dupuytren's contracture, a midhumeral block was used with the musculocutaneous and radial nerves blocked by lidocaine and the median and ulnar nerves blocked with bupivacaine. Recovery of motor function and time to discharge were shorter compared with patients who received the mixture on all four nerves.

The orthogonal two-needle technique: a new axillary approach to the brachial plexus.

Ninety-eight patients scheduled for elbow, forearm, wrist or hand surgery were allocated randomly to one of two different techniques of brachial plexus block, both using the axillary approach. The blocks were all performed at the level of the insertion of the lateral margin of the pectoralis major muscle on the humerus. The same mixture and volume of anaesthetic solution (30 mL of a mixture of equal parts of 0.5% bupivacaine with adrenaline 1:200 000 and 2% lignocaine) was injected through two needles positioned above and below the axillary artery, in the fascial compartments containing the median and ulnar nerves, respectively. Confirmation of correct needle placement was obtained by elicitation of paraesthesias. In one group of patients (n = 40) the needles were inserted parallel to the axillary artery pathway and the anaesthetic solution was injected toward the apex of the axilla. In a second group (n = 58) the needles were inserted orthogonally with respect to the neurovascular bundle pathway, aimed towards the posterior fascial compartment containing the radial nerve. Using the second technique, all the terminal branches of the brachial plexus were more frequently involved in the block, including the distribution of the musculocutaneous nerve. It seems likely that the inclination of the needles causes a preferential spread of the anaesthetic solution which follows the direction of the needle shaft.

[Locoregional anesthesia of the foot for forefoot surgery]. / Anesthésie locorégionale du pied pour chirurgie de l'avant-pied.

A technique of regional anaesthesia of the foot for forefoot surgery (ingrowing toe-nail, hallux valgus, amputation, etc.) is described. It consists of a block of the superficial peroneal nerve at the ankle combined with a block of the posterior tibial nerve behind the medial malleolus. A volume of 5-6 ml of 1% lidocaine or 1% mepivacaine is injected. A pneumatic tourniquet was placed on the upper part of the thigh after the patient had been given an intramuscular premedication. The results of 52 such blocks carried out in 40 patients are discussed.

[Peripheral neuropathy due to N-hexane in a drug addict (author's transl)]. / Neuropathie périphérique au N-hexane chez une toxicomane.

After voluntary inhalation of a domestic solvent containing N-Hexane and N-Heptane for three months, a 23-year-old woman developed motor deficit of the lower limbs, sensory symptoms and areflexia. Clinical disorders continued to progress after discontinuation of the intoxication, with a parallel aggravation of the E.M.G. disturbances. A nerve biopsy with ultrastructural study showed axon dilatation with accumulation of neurofilaments. The clinical, electrophysiological and pathological features of neuropathies induced by hexacarbon solvents are reviewed and their pathogenesis is discussed.