Unsolicited paresthesias with nerve stimulator: case reports of four patients

IMPLICATIONS: Unsolicited paresthesias may occur when a nerve stimulator is used and may indicate valid proximity to the nerve. This phenomenon suggests that nerve stimulator use does not protect against unplanned direct contact with peripheral nerves during performance of a nerve block on an obtunded patient.     

Axillary block complicated by hematoma and radial nerve injury.

BACKGROUND AND OBJECTIVES: Hematoma is typically cited as one mechanism of nerve injury following axillary block. However, documented cases of this are lacking. METHODS: A healthy 38-year-old man was scheduled for surgical removal of a tumor of the hand. A transarterial axillary block was performed with a 22-gauge short-bevel needle using 40 mL of a mixture of equal volumes of 1.5% lidocaine and 0.5% bupivacaine containing 1:200,000 epinephrine. No paresthesias were reported. Postoperative, the patient developed a large axillary hematoma accompanied by paresthesias and radial nerve weakness. RESULTS: With conservative management, nerve recovery was complete in 6 months. CONCLUSIONS: Hematoma complicating axillary block may result in nerve dysfunction.     

Regional nerve block for femoropopliteal and tibial arterial reconstructions

Thirteen high-risk patients underwent lower extremity revascularization anesthetized with a regional nerve block technique. The sciatic, femoral, and obturator nerves were infiltrated with 1% lidocaine and 0.25% bupivacaine. Eight femoropopliteal and five femorotibial bypasses were performed for limb salvage (11 patients), disabling claudication (one patient), and popliteal artery aneurysm (one patient). Analgesia was adequate with only one patient who needed supplemental nitrous oxide. One patient died on the sixth postoperative day of a myocardial infarction. Regional nerve block is an effective anesthetic technique that should be considered if general or spinal anesthesia is inappropriate.     

Incidence of pneumothorax from intercostal nerve block for analgesia in rib fractures

BACKGROUND: The incidence of pneumothorax (PTX) after individual intercostal nerve block (INB) for postoperative pain reportedly varies from 0.073% to 19%.1-3 This study investigated the incidence of PTX after INB for rib fractures. METHODS: We conducted a retrospective chart review of patients admitted between January 1996 and December 1999 with rib fractures who received INB. RESULTS: One hundred sixty-one patients received 249 intercostal nerve block procedures (INBPs). An INBP is one session where a set of intercostal nerves are blocked. A total of 1,020 individual intercostal nerves were blocked. There were 14 pneumothoraces. The overall incidence of PTX per patient was 8.7%, with an incidence of PTX per INBP of 5.6%. The incidence of PTX was 1.4% for each individual intercostal nerve blocked. CONCLUSION: The incidence of PTX per individual intercostal nerve blocked is low. INB is an effective form of analgesia, and for most patients with rib fractures one INBP is sufficient to allow adequate respiratory exercises and discharge from the hospital.     

Ultrasound-guided popliteal block demonstrates an atypical motor response to nerve stimulation in 2 patients with diabetes mellitus

BACKGROUND AND OBJECTIVES: Nerve stimulation is a useful technique to identify peripheral nerves before blockade. We report 2 cases of the failure of nerve stimulation to accurately localize the sciatic nerve in patients with diabetes mellitus undergoing outpatient foot procedures. We also introduce a novel approach to performing a popliteal fossa block using ultrasound guidance. CASE REPORT: Ultrasound-guided popliteal fossa blocks were performed in 2 patients with diabetes mellitus. Both patients failed to develop an appropriate motor response or paresthesia to nerve stimulation. The needle positions were confirmed by ultrasound guidance and injections of local anesthesia were made uneventfully. Appropriate surgical anesthesia was established and the procedures were performed uneventfully. CONCLUSION: Ultrasound facilitated the accurate localization of the sciatic nerve in 2 patients with diabetes mellitus. Neither patient had a paresthesia or muscle twitch below 2.4 mA. There is theoretical concern that patients with underlying neuropathy, such as patients with diabetes mellitus, may have an altered response to either motor or sensory stimulation.     

Fibrolipoma of the median nerve: a case report and review of the literature

A 38 year-old patient presented with right median nerve distribution paresthesias. Electrodiagnostic studies confirmed severe carpal tunnel syndrome. A palmar mass prompted a magnetic resonance imaging scan, which suggested a fibrolipoma of the median nerve. Carpal tunnel release resulted in resolution of preoperative pain and paresthesias. We review the literature dealing with this primary nerve tumor.     

Bilateral axillary brachial plexus block guided by multiple nerve stimulation and ultrasound in a multiple trauma patient

We present the case of a woman with multiple wounds and injuries after attempted suicide by jumping from a high place. She had multiple craniofacial injuries and fractures of both forearms requiring emergency osteosynthesis. The neurosurgeons requested that a level of consciousness be maintained for frequent assessment; therefore it was decided to provide a bilateral axillary brachial plexus block. The procedure was carried out with the aid of a nerve stimulator to locate a triple response in the left arm (radial, medial and musculocutaneous nerves) and with both ultrasound and double nerve stimulation in the right arm (medial and radial nerves). Surgery proceeded without adverse events. The location of nerves or nerve roots with both ultrasound and stimulators was highly useful in this patient in need of bilateral brachial plexus blockade. This combination, and ultrasound in particular, might be the technique of choice because it offers an image in real time and assessment of the least amount of anesthetic that seems to be needed for achieving a block.     

Ultrasound imaging for popliteal sciatic nerve block

BACKGROUND AND OBJECTIVES: Ultrasound is a novel method of nerve localization but its use for lower extremity blocks appears limited with only reports for femoral 3-in-1 blocks. We report a case series of popliteal sciatic nerve blocks using ultrasound guidance to illustrate the clinical usefulness of this technology. CASE REPORT: The sciatic nerve was localized in the popliteal fossa by ultrasound imaging in 10 patients using a 4- to 7-MHz probe and the Philips ATL HDI 5000 unit. Ultrasound imaging showed the sciatic nerve anatomy, the point at which it divides, and the spatial relationship between the peroneal and tibial nerves distally. Needle contact with the nerve(s) was further confirmed with nerve stimulation. Circumferential local anesthetic spread within the fascial sheath after injection appears to correlate with rapid onset and completeness of sciatic nerve block. CONCLUSIONS: Our preliminary experience suggests that ultrasound localization of the sciatic nerve in the popliteal fossa is a simple and reliable procedure. It helps guide block needle placement and assess local anesthetic spread pattern at the time of injection.     

Carpal tunnel syndrome: associated abnormalities in ulnar nerve function and the effect of carpal tunnel release on these abnormalities

Twenty of 59 hands (34%) of patients with carpal tunnel syndrome had abnormalities in sensibility testing of both median and ulnar nerves by either two-point discrimination, Semmes-Weinstein monofilament testing, or both. Before surgery, 53% of patients complained of paresthesias and/or numbness in ulnar nerve distribution. Eighty percent of the hands had abnormal Semmes-Weinstein monofilament testing of the ulnar nerve. Thirty-five percent had abnormal two-point discrimination. Forty-one percent had abnormal electromyographic testing of the ulnar nerve. All hands had median nerve decompression alone. Guyon's canal was not released. After surgery, 89% of patients had improvement in paresthesias and/or numbness of the ulnar nerve. Ninety-four percent had improvement in Semmes-Weinstein monofilament testing. Eighty-six percent had improvement in two-point discrimination. Patients with a residual abnormality in ulnar nerve sensibility also had continued abnormality in median nerve sensibility. A significant percentage of patients with carpal tunnel syndrome also have signs and symptoms of ulnar nerve compression. Most improved with carpal tunnel release alone.     

Muscle weakness and paresthesia associated with epidural analgesia in a patient with an intrathecal neurofibrolipoma as part of a tethered cord syndrome

We report a case of a 75-yr-old female patient in whom motor deficits and paresthesias occurred after lumbar epidural analgesia. These symptoms were eventually found to be due to a tethered cord syndrome. An epidural catheter was inserted for analgesia after colon surgery. The postoperative course was characterized by fluctuating sensory and motor symptoms. A magnetic resonance imaging scan showed an intraspinal mass, which was removed by laminectomy. The presented complication is of major interest because the intraspinal tumor, which must have been present for years, became acutely symptomatic. Tethered cord syndrome is caused by a limited longitudinal mobility of the cord. It is often seen as a part of spinal closure defects and is also associated with intrathecal tumors. Typically, adult patients complain of weak legs, paresthesias of the legs, and urinary incontinence. However, our patient had denied any muscular or neurological problems or urinary incontinence during the preoperative interview. Postoperative electromyogram and electroneurography ascertained chronic neurogenic lesions of multiple lumbar and sacral nerve roots. Three months after the operation, the patient was able to walk 100 m with a crutch.     

Peripheral nerve entrapments

Peripheral nerve entrapment is a rare, but important, cause of foot and ankle pain that often is underdiagnosed and mistreated. A peripheral nerve may become entrapped anywhere along its course, but certain anatomic locations are characteristic. Clinically,nerve entrapment is divided into three stages: in stage I patients feel rest pain and intermittent paresthesias which are worse at night; in stage II, continued nerve compression leads to paresthesias, numbness, and, occasionally, muscle weakness that does not disappear during the day, and in stage III, patients describe constant pain, muscle atrophy, and permanent sensory loss. Diagnostic confusion abounds because of the multiple etiologies of peripheral nerve entrapments and their complex physical and temporal relation. A thorough understanding of the causes of peripheral nerve entrapments, the anatomic course and variation of the peripheral nerves, the diagnostic modalities, and the treatment options can simplify this complex problem.     

The enhancement of sensory blockade by clonidine selectively added to mepivacaine after midhumeral block

Clonidine added to local anesthetics results in an increased duration of anesthesia or analgesia after brachial plexus block. We investigated the effect of selective application of clonidine to the median and musculocutaneous nerves during midhumeral block, a technique allowing selective nerve blocks with the use of different local anesthetics. Initially, 58 patients scheduled for hand surgery were prospectively enrolled to receive a midhumeral block. These patients were randomly allocated into two groups. The Control group (n = 28) received 10 mL of plain mepivacaine 1.5% for each nerve (median, musculocutaneous, ulnar, and radial). The Clonidine group (n = 30) received 10 mL of plain mepivacaine 1.5% for each nerve, but the median and musculocutaneous nerves also received a dose of 50 microg clonidine. One patient in the Control group and two patients in the Clonidine group with a failed block were therefore excluded from the analysis. The onset time of surgical anesthesia was recorded. The durations of sensory and motor blocks were checked every 15 min. The plasma mepivacaine concentration was analyzed from 10 patients in each group. Onset times for complete sensory block were similar between the two groups. Adding 50 microg clonidine to the median and musculocutaneous nerves resulted in a significant increase in the duration of sensory block in these nerves (P < 0.0001). Recovery of motor block was not different between the two groups. No significant difference was found between the two groups in the mean plasma mepivacaine concentration.     

Axillary plexus block using a peripheral nerve stimulator: single or multiple injections

This prospective, randomized, double-blind study was undertaken to evaluate the success rates of axillary brachial plexus block performed with the help of a peripheral nerve stimulator when either one, two or four of the major nerves of the brachial plexus were located. Seventy-five patients undergoing upper limb surgery were randomly allocated to one of the following five groups according to the nerve and number of nerves to be located; G-1: musculo-cutaneous, radial, median and ulnar nerves; G-2: musculo-cutaneous plus one of the other three nerves; G-3: radial nerve; G-4: median nerve; G-5: ulnar nerve. The sensory block was evaluated before surgery and cutaneous anaesthesia was considered to be present when the needles of a Wartenberg Pinwheel were no longer felt in all the dermatomes of the nerves implicated in the surgical site. Otherwise, the block was considered to need completion before surgery. Only one out of the 15 patients in G-1 and G-2 needed completion of their block before surgery whereas seven out of 15 for G-3 and eight out of 15 for G-4 and G-5 needed completion of their block (P less than 0.01). We conclude that when performing an axillary block with the help of a peripheral nerve stimulator, stimulation of the musculo-cutaneous nerve and one other nerve or stimulation of all four major nerves of the brachial plexus gives a higher success rate than stimulation of only one nerve, whether the stimulated nerve is the median, radial or ulnar.     

Noninvasive ankle distraction: Relationship between force,magnitude of distraction,and nerve conduction abnormalities

Seven healthy volunteers (14 ankles: four males, 3 females) with no history of ankle or foot pathology were placed in a modified beach chair position on an operating table for ankle distraction using a noninvasive ankle distractor. In-line traction of 0 to 225 N (50 lb) in 22.5-N (5-lb) increments was applied to tne ankle. A direct lateral radiograph was obtained at each distraction force. The joint space was measured on the lateral radiographs using electronic microcalipers. Surface recordings of the superficial peroneal, deep peroneal dorsal digital cutaneous, and sural nerves were obtained. The ankle joint space increased progressively from an average 3.1 mm with no force applied to an average 4.2 mm with 225 N (50 lb) distraction force applied. The maximum joint distraction averaged 1.3 mm (range, 0.35 to 2.35 mm). The sensory amplitudes were diminished or absent with increasing time and force of distraction. The decreased amplitudes were most marked after 1 hour of distraction with 135 N (30 lb) or greater distraction force. This correlated with symptoms of paresthesias. The superficial and deep peroneal cutaneous nerves were affected to a much greater extent than the sural nerve. The amplitudes quickly returned to normal values with the weight being released from the ankle. The noninvasive ankle distractor safely increased ankle joint space by more than 1 mm. Distraction with 135 N (30 lb) or more for 1 hour is associated with reversible nerve conduction changes. Based on these findings, we recommend using the noninvasive ankle distraction apparatus for ankle arthroscopy, with up to 135 N (30 lb) of traction applied to the foot for up to 1 hour. Greater force, applied for longer periods, is associated with increasing nerve conduction abnormalities.     

Applying ultrasound imaging to interscalene brachial plexus block

OBJECTIVE: Previous studies have examined ultrasound-assisted brachial plexus blocks, but few have applied this imaging technology to the interscalene region. We report a case of interscalene brachial plexus block using ultrasound guidance to show the clinical usefulness of this technology. CASE REPORT: A nerve stimulator-guided interscalene block was attempted for arthroscopic shoulder surgery but failed. Subsequent nerve localization was accomplished by ultrasound imaging using a high-frequency probe (5-12 MHz) and the Philips ATL HDI 5000 unit. Ultrasound showed nerves between the scalene muscles, block needle movement at the time of advancement, and local anesthetic spread during injection. Interscalene block was successful after 1 attempt of nerve localization and needle placement. CONCLUSIONS: Advanced ultrasound technology is useful for nerve localization and can generate brachial plexus images of high resolution in the interscalene groove, guide block needle placement and advancement in real time to targeted nerves, and assess adequacy of local anesthetic spread at the time of injection. Ultrasound imaging guidance can potentially improve success during interscalene brachial plexus block.     

Diagnostic lumbosacral segmental nerve blocks with local anesthetics: a prospective double-blind study on the variability and interpretation of segmental effects

BACKGROUND AND OBJECTIVES: Selective spinal nerve infiltration blocks are used diagnostically in patients with chronic low back pain radiating into the leg. Generally, a segmental nerve block is considered successful if the pain is reduced substantially. Hypesthesia and elicited paresthesias coinciding with the presumed segmental level are used as controls. The interpretation depends on a standard dermatomal map. However, it is not clear if this interpretation is reliable enough, because standard dermatomal maps do not show the overlap of neighboring dermatomes. The goal of the present study is to establish if dissimilarities exist between areas of hypesthesia, spontaneous pain reported by the patient, pain reduction by local anesthetics, and paresthesias elicited by sensory electrostimulation. A secondary goal is to determine to what extent the interpretation is improved when the overlaps of neighboring dermatomes are taken into account. METHODS: Patients suffering from chronic low back pain with pain radiating into the leg underwent lumbosacral segmental nerve root blocks at subsequent levels on separate days. Lidocaine (2%, 0.5 mL) mixed with radiopaque fluid (0.25 mL) was injected after verifying the target location using sensory and motor electrostimulation. Sensory changes (pinprick method), paresthesias (reported by the patient), and pain reduction (Numeric Rating Scale) were reported. Hypesthesia and paresthesias were registered in a standard dermatomal map and in an adapted map which included overlap of neighboring dermatomes. The relationships between spinal level of injection, extent of hypesthesia, location of paresthesias, and corresponding dermatome were assessed quantitatively. Comparison of the results between both dermatomal maps was done by paired t-tests. RESULTS: After inclusion, data were processed for 40 segmental nerve blocks (L2-S1) performed in 29 patients. Pain reduction was achieved in 43%. Hypesthetic areas showed a large variability in size and location, and also in comparison to paresthesias. Mean hypesthetic area amounted 2.7 +/- 1.4 (+/- SD: range, 0 to 6; standard map) and 3.6 +/- 1.8 (0 to 6; adapted map; P <.001) dermatomes. In these cases, hypesthesia in the corresponding dermatome was found in 80% (standard map) and 88% of the cases (adapted map, not significant). Paresthesias occurring in the corresponding dermatome were found in 80% (standard map) compared with 98% (adapted map, P <.001). In 85% (standard map) and 88% (adapted map), spontaneous pain was present in the dermatome corresponding to the level of local anesthetic injection. In 55% (standard map) versus 75% (adapted map, P <.005), a combination of spontaneous pain, hypesthesia, and paresthesias was found in the corresponding dermatome. CONCLUSIONS: Hypesthetic areas determined after lumbosacral segmental nerve blocks show a large variability in size and location compared with elicited paresthesias. Confirmation of an adequately performed segmental nerve block, determined by coexistence of hypesthesia, elicited paresthesias and pain in the presumed dermatome, is more reliable when the overlap of neighboring dermatomes is taken into account.     

Tremor and peripheral nerve entrapment. Case report

A patient is described in whom pain, paresthesias, weakness, and resting tremor gradually developed 8 years after an ulnar nerve transposition. Electromyography revealed that the tremor occurred at 4 to 5 Hz, was abolished by voluntary muscle contraction, and was localized to ulnar-innervated muscles. Ulnar nerve conduction was focally slowed at the elbow; therefore, ulnar neurolysis was performed and a fusiform neuroma-in-continuity was found. Mechanically tapping the neuroma elicited repetitive discharges at 4 to 5 Hz in the intrinsic muscles of the hand; these discharges were abolished by anesthetic block proximal to the neuroma. Although the pain, paresthesias, and weakness were abolished by the neurolysis, the tremor persisted. Possible neurophysiological mechanisms underlying the appearance of tremor with peripheral nerve entrapment are discussed.     

Secondary digital nerve repair in the foot with resorbable p(DLLA-epsilon-CL) nerve conduits

Nerve guides are increasingly being used in peripheral nerve repair. In the last decade, much preclinical research has been undertaken into a resorbable nerve guide composed of p(DLLA-epsilon-CL). This report describes the results of secondary digital nerve reconstruction in the foot in a patient with post-traumatic neuromas of the common plantar digital nerves II-III and III-IV. The neuromas were resected and reconstruction of the nerves was carried out with resorbable Neurolac nerve guides. The Pressure Specified Sensory Device was used to measure the static (s) and moving (m) 1- and 2-point discrimination (PD). Fourteen months after nerve repair, the m1-PD returned in all digital nerves. The s1-PD returned only on the lateral side of the second toe. The m2-PD and s2-PD did not return in any of the toes originally innervated by the reconstructed nerves. According to the British Classification System, the sensory nerve recovery was poor. However, there were no complaints of painful neuromas after this procedure. In conclusion, this report shows no beneficial effects of Neurolac nerve guides in terms of return of sensibility after repair of common plantar digital nerves. Painful neuromas, however, could be well-treated.