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Paresthesiae or no paresthesiae? Nerve lesions after axillary blocks.

Seeking paresthesiae when performing a peripheral nerve block may increase the risk of post-anesthetic neurological sequelae. To test this hypothesis, we prospectively followed two groups of patients who underwent hand surgery with an axillary block. In one group, the axillary plexus was located by actively seeking paresthesiae; in the other, pulsations of the axillary artery indicated an adequate position of the injection needle. Mepivacaine 10 mg/ml, with or without adrenaline, was used. The study included 533 patients, 290 in the paresthesia group and 243 in the artery group. Although unintentional, paresthesiae were elicited in 40% of patients in the artery group. Postanesthetic nerve lesions were seen in ten patients, eight in the paresthesia group and two in the artery group, all of whom had been blocked by mepivacaine with adrenaline. Symptoms varied between light paresthesiae lasting a few weeks, and severe paresthesiae, ache and paresis lasting more than 1 year. The etiology suspected was needle and perhaps injection trauma to the nerves during blocking. We conclude that whenever possible nerve blocks should be performed without searching for paresthesiae.

Adult↗

Risk factors for unpleasant paresthesiae induced by paresthesiae-producing deep brain stimulation.

Paresthesiae-producing deep brain stimulation (stimulation of ventrocaudal nucleus-VC, medial lemniscus-ML or internal capsule-IC) is one of the few procedures to treat the steady element of neural injury pain (NIP) currently available. Reviewing the first 60 patients with NIP submitted to deep brain stimulation (DBS) from 1978 to 1991 at the Division of Neurosurgery, Toronto Hospital, University of Toronto, we observed that 6 patients complained of unpleasant paresthesiae with paresthesiae-producing DBS, preventing permanent electrode implantation in all of them. Such patients accounted for 15% of the failures (6 out of 40 failures) in our series. In an attempt to improve patient selection, we reviewed our patients considering a number of parameters in order to determine risk factors for unpleasant paresthesiae elicited by paresthesiae-producing DBS. The results showed that this response happened only in patients with brain central pain complaining of evoked pain, secondary to a supratentorial lesion. Age, sex, duration of pain, quality of the steady pain, size of the causative lesion and site (VC,ML,IC) and type (micro or macroelectrode) of surgical exploration were not important factors. Unpleasant parethesiae in response to dorsal column stimulation, restricted thalamic lesion on computed tomography and the occurrence of associated intermittent pain were considered major risk factors in this subset of patients and the presence of cold allodynia or hyperpathia in isolation and the absence of sensory loss were considered minor risk factors. It is our hope that the criteria here established will improve patient selection and so, the overall results of DBS.

Adult↗

Characterization of different paresthesias following orthognathic surgery of the mandible.

PURPOSE: Paresthesia is a well known consequence of peripheral nerve injury. However, the neural mechanisms of the 2 recognized types, spontaneous and elicited, are currently unknown. This study aimed to investigate these 2 paresthesias and the possible mechanisms accompanying orthognathic surgery. PATIENTS AND METHODS: Mechanical-touch thresholds and current perception threshold were measured before and 7 days after surgery in 60 chin sites (mental nerve area) of 30 patients who underwent orthognathic surgery. Similar testing was conducted on healthy volunteers (controls). All sites were classified by the presence or absence of each paresthesia: spontaneous paresthesia or no spontaneous paresthesia, and elicited paresthesia or no elicited paresthesia. Presence or absence analyses were followed-up for 6 weeks after surgery. RESULTS: Gender differences and maxillary surgery did not change the incidence of paresthesia during postoperative week 1 (chi-square test, P > .05). A significantly higher mechanical-touch threshold was observed with spontaneous paresthesia compared with no spontaneous paresthesia (Mann-Whitney U-test; P < .05), but not between no elicited paresthesia and elicited paresthesia (Mann-Whitney U-test; P > .05). A significant increase in postsurgery current perception thresholds values compared with presurgery values was observed at 2,000 Hz in spontaneous paresthesia, and at 2,000 and 5 Hz in elicited paresthesia (paired t test, P < .05). The incidence of spontaneous paresthesia decreased more rapidly than elicited, while the latter tended to increase again during the 6-week postsurgical test period. CONCLUSION: The results suggested that both spontaneous and elicited paresthesias are associated with damage and dysfunction in myelinated primary afferent fibers, but additional neural mechanisms are implicated during elicited paresthesia.

Adolescent↗

Temporal excitation properties of paresthesias evoked by thalamic microstimulation.

OBJECTIVE: The neuronal elements mediating the effects of deep brain stimulation (DBS) are unknown. The objective was to determine the strength-duration properties of the neuronal elements that mediate paresthesias evoked by thalamic microstimulation. METHODS: The strength-duration properties of the neuronal elements causing paresthesias were measured using intraoperative microstimulation of the human thalamus. The sample included both concordant (reported in the same region as the mapped sensory receptive fields) and discordant paresthesias (reported in a region different than the mapped sensory receptive fields). RESULTS: There were no significant differences between the chronaxies of concordant and discordant paresthesias. There was no significant correlation between chronaxie and rheobase for concordant paresthesias, but a strong negative correlation existed for discordant paresthesias. CONCLUSIONS: Chronaxies did not distinguish the neuronal elements mediating concordant and discordant paresthesias, but correlations between chronaxie and rheobase suggest that concordant paresthesias were produced by activation of local cells while discordant paresthesias were caused by activation of axons of passage. SIGNIFICANCE: The similarity between the strength-duration properties of paresthesias evoked by thalamic stimulation, tremor reduction evoked by thalamic DBS, and EMG responses to thalamic DBS does not mean that these effects are caused by the same neural elements.

Chronaxy↗

Interscalene brachial plexus block for shoulder surgery: a proximal paresthesia is effective.

This study was designed to determine whether the location of paresthesias is related to the success of interscalene blocks in providing anesthesia for shoulder surgery. Interscalene blocks were performed in 45 patients presenting for elective shoulder surgery. Interscalene injections of 33-55 mL of 1.5% mepivacaine with epinephrine were performed after the first elicited paresthesia to the shoulder, arm, forearm, or hand. In 20 patients (45%), the initial elicited paresthesia was to the shoulder, whereas in 25 patients (55%), the first paresthesia was reported as distal to the shoulder. All patients developed brachial plexus anesthesia adequate for shoulder surgery. The time-course of onset of motor block as evaluated at the shoulder and elbow was not different between patients with shoulder paresthesias and those with more distal paresthesias. Handgrip strength was quantitatively evaluated with a dynamometer, and both paresthesia groups showed similar decrements in hand strength except at the end of the measurement period, when patients with distal paresthesias had a significantly weaker handgrip than patients with shoulder paresthesias. We recommend that paresthesias to the shoulder be accepted in performing interscalene blocks for patients undergoing shoulder surgery.

Adult↗

Clinical evaluation of paresthesia steering with a new system for spinal cord stimulation.

OBJECTIVE: The goal was to evaluate, in a clinical study, the predicted performance of the transverse tripolar system for spinal cord stimulation, particularly the steering of paresthesia, paresthesia coverage, and the therapeutic range of stimulation. METHODS: Six transverse tripolar electrodes were implanted in the lower thoracic region in four patients experiencing chronic neuropathic pain. Electrode positions, relative to the spinal cord, were estimated from computed tomographic scans. A dual-channel stimulator was used for initial percutaneous tests, and an implanted single-channel stimulator was used for follow-up test sessions. Nine "balance" settings and several cathode-anode combinations were used with the dual-channel and single-channel stimulator, respectively. In each test, the increase of paresthesia coverage from the perception threshold to the discomfort threshold was registered on a body map and the corresponding voltages were recorded. RESULTS: Paresthesia steering occurred in all but one patient. The normalized steering score, enabling quantitative comparisons of paresthesia steering among tests and patients, showed that maximum paresthesia steering occurred when the electrode was at least 3 mm dorsal to the spinal cord and centered <2 mm from its midline. Paresthesia coverage included 70 to 100% of the body up to the electrode level, unless the electrode migrated or had broken wires. The therapeutic range, defined as the discomfort/perception of paresthesia threshold ratio, varied from 1.6 to 4.0. CONCLUSION: The clinical performance of transverse tripolar stimulation is in accordance with the characteristics predicted by computer modeling. It enables finer control of paresthesia than that achieved by polarity changes in conventional spinal cord stimulation systems.

Adult↗

Ischemic compression paresthesias in Guillain-Barré syndrome.

An experiment in nine patients tested the similarities and interactions between the paresthesias of Guillain-Barré syndrome (GBS) and tourniquet-induced compression paresthesias. During brachial compression, GBS paresthesias diminished in five of seven patients and new paresthesias occurred in two patients with purely motor GBS. Beginning 1 to 4 minutes after release of the cuff, all patients had new paresthesias, distinguishable from GBS symptoms. The novel finding was that GBS paresthesias diminished or ceased during the postcompression period in five of seven patients. Demyelinated peripheral nerves in GBS apparently can generate and transmit the spontaneous activity associated with paresthesias in the postcompression period. Interference occurs between the two types of paresthesias, possibly because both are caused by spontaneous ectopic activity in tactile nerves.

Foot↗

Inability to consistently elicit a motor response following sensory paresthesia during interscalene block administration.

BACKGROUND: Two methods of nerve block based on eliciting neural feedback with the block needle currently exist. The paresthesia technique uses sensory feedback to ascertain that the needle tip is close to the nerve. By contrast, a peripheral nerve stimulator makes use of motor responses to electrical stimulation. The relation of motor responses to an electrical peripheral nerve stimulator and sensory nerve contact (paresthesia) had not been studied. METHODS: Thirty consecutive unpremedicated patients who presented for shoulder surgery with interscalene block anesthesia were prospectively studied. Interscalene block was performed by the single paresthesia method of Winnie, using an insulated or non-insulated needle connected to a peripheral nerve stimulator with the power off. At the precise point of paresthesia, the peripheral nerve stimulator was turned on, and the current was slowly increased to 1.0 mA with a pulse width of 0.2 ms. Presence and location of any motor responses were observed and recorded. RESULTS: All patients had easily elicited paresthesias. The site of first paresthesia was to the shoulder in 73% of patients. Only 30% of patients exhibited any motor response to electrical stimulation up to 1.0 mA. There was no relation between site of paresthesia and associated motor nerve response. CONCLUSION: Elicitation of paresthesia does not translate to an ability to elicit a motor response to a peripheral nerve stimulator in the majority of patients.

Electric Stimulation↗

Backpacking-induced paresthesias.

OBJECTIVE: To evaluate the presence of numbness and paresthesias among long-distance backpackers on the Appalachian Trail. METHODS: Backpackers who hiked a minimum of 7 days were interviewed while hiking. Following their hike, a written questionnaire was mailed to the participants that explored the incidence of injuries and illnesses among hikers. Paresthesias were defined as either numbness or "phantom, burning, or shooting pains." A case-control analysis of risk factors for paresthesias was performed. RESULTS: Paresthesias were reported by 34% (96 of 280) of the backpackers completing the study. They included ulnar paresthesias (n = 4), meralgia paresthetica (n = 10), tarsal tunnel syndrome (n = 6), digitalgia paresthetica (n = 21), and nonspecific paresthesias (n = 61). The most common symptom was numbness: 81% (78 of 96). Significant risk factors included a distance of >2000 miles (relative risk [RR] = 1.3; 95% CI, 1.1-1.6; P = .01) and the duration of hiking (RR = 2.0; 95% CI, 1.2-3.2; P = .004) for the longest quartile. Nonsignificant factors included backpack weight, initial body weight, percentage of weight loss, running shoe usage, and multivitamin usage. Ninety-eight percent of the paresthesias (94 of 96) had resolved by the time of follow-up (median = 30 days). CONCLUSIONS: Paresthesias were a surprisingly common complaint among long-distance backpackers. Although they were distressing during backpacking, these neuropathies were self-limited and resolved after completion of hiking.

Adult↗

Area of paresthesia as determinant of sensory block in axillary brachial plexus block.

BACKGROUND AND OBJECTIVES: Paresthesia is widely considered a useful indicator for locating components of the brachial plexus using the axillary approach. While establishing axillary brachial plexus blocks, the authors attempted to correlate the area of paresthesia with the effectiveness of the sensory block. METHODS: Axillary brachial plexus blocks were established in 222 consecutive adult patients scheduled for elective surgery of the hand or forearm. After paresthesia was elicited in the distribution of one of the three terminal nerves of the hand (median, radial, or ulnar nerve), 30 microliters 1.5% mepivacaine without epinephrine was injected after advancing an indwelling catheter. Sensory block of each terminal nerve was assessed 20 minutes after the injection. RESULTS: The median and radial nerves were blocked with the highest reliability (87% and 93%, respectively) after paresthesia was elicited in the areas supplied by the corresponding nerves. The ulnar nerve was blocked most reliably ( > 85%) after the elicitation of paresthesia in its area of distribution as well as when no paresthesia was induced. The most reliable block of the musculocutaneous nerve (72%) was achieved after paresthesia was induced in the area supplied by the median nerve. CONCLUSION: Eliciting paresthesia at the nerve supplying the area of a planned surgical incision is a reliable determinant of successful axillary brachial plexus block.

Adult↗

Incidence of chest wall paresthesia after video-assisted thoracic surgery for primary spontaneous pneumothorax.

OBJECTIVE: Video-assisted thoracic surgery (VATS) is an established treatment for recurrent or complicated primary spontaneous pneumothorax (PSP). However, a proportion of patients still complains of chronic pain or discomfort after VATS pleurodesis. We aimed to investigate if paresthesia is a distinct component of the post-operative discomfort in patients receiving VATS for PSP. METHODS: Telephone interviews were conducted with 52 patients who had received VATS pleurodesis for PSP in our institute during a defined 24 month period. A standardized questionnaire was used to identify paresthetic discomforts which the patients themselves could distinguish from their wound pain. Responses were obtained from 51 patients (42 male, 9 female) with a mean age of 24.1 years (range 14-63 years), giving a response rate of 98.0%. RESULTS: With a median observation time of 19 months (range 2-24 months), 27 patients (52.9%) reported experiencing paresthesia as a post-operative complication distinct from their wound pain. The most commonly described characteristics of the paresthesia were 'pins and needles' (37.0%), 'numbness' (25.9%) or a sensation of abnormal 'swelling' in the chest wall (11.1%). Although only two of the affected patients (7.4%) described the paresthesia as 'severe', consequent functional disturbances in daily life were noted by seven patients (25.9%), and 11 patients (40.7%) actively sought medical or alternative, holistic therapies to relieve the paresthesia. Eight (21.0%) of the 38 patients followed-up for over 12 months after surgery still experienced the paresthesia. CONCLUSIONS: Although it should not detract from the proven advantages of VATS, paresthesia in the chest wall represents a distinct but previously overlooked post-VATS complication. It is a potential source of significant post-operative morbidity, and may run a chronic course in some patients. Further study is warranted to elucidate its mechanisms and optimum management.

Adolescent↗

Incidence of chest wall paresthesia after needlescopic video-assisted thoracic surgery for palmar hyperhidrosis.

OBJECTIVE: Chest wall paresthesia is a reported sequela of thoracotomy and Video-Assisted Thoracic Surgery (VATS) which is distinct from wound pain. Although needlescopic VATS confers less post-operative pain and better cosmesis, the incidence of paresthesia after needlescopic VATS has not been quantified. METHODS: For homogeneity of the patient cohort, we studied 50 patients who received bilateral needlescopic VATS sympathectomy (T2-T4 excision) for palmar hyperhidrosis using 2 or 3 mm instruments during a 36-month period at a single institute. A standard questionnaire was administered by telephone interview, with 34 patents responding (68.0%). The median post-operative observation time was 16.5 months (range: 10-40 months). Collected data were compared with a historical group who received conventional VATS using 10 mm ports. RESULTS: Paresthetic discomfort distinguishable from wound pain was described by 17 patients (50.0%). The most common descriptions were of 'bloating' (41.2%), 'pins and needles' (35.3%), or 'numbness' (23.5%) in the chest wall. The paresthesia resolved in less than two months in 12 patients (70.6%), but was still felt for over 12 months in three patients (17.6%). Post-operative paresthesia and pain did not impact on patient satisfaction with the surgery, whereas compensatory hyperhidrosis in 24 patients (70.6%) did (P=0.001). The rates and characteristics of the paresthesia following needlescopic VATS are similar to those observed after conventional VATS. CONCLUSIONS: Chest wall paresthesia affects a significant but previously overlooked proportion of patients following needlescopic VATS, but has minimal impact on post-operative satisfaction. Needlescopic VATS offers no apparent advantage over conventional VATS with regard to paresthesia.

Adolescent↗

Painful paresthesiae are infrequent during brachial plexus localization using low-current peripheral nerve stimulation.

BACKGROUND: Considerable controversy exists over the relationship of paresthesia to nerve stimulation. The purpose of this study was to determine the frequency with which patients report paresthesia at the point that an acceptable motor response is obtained to low-intensity current electrical stimulation. METHODS: Low-intensity current nerve stimulation (0.6 mA, 200 microseconds, 2 Hz) was used to identify the brachial plexus in 64 consecutive patients having shoulder or arm surgery with an interscalene block. During nerve localization and while maintaining a motor response (0.20 mA-0.40 mA), the patients were queried regarding any radiating sensation or pain (paresthesia) in the shoulder or extremity on the side of the blockade. Sensory distribution of the block, motor strength of the arm muscles, and adequacy of anesthesia were used to assess the extent of blockade. RESULTS: Ninety-five percent of patients had satisfactory surgical anesthesia. None of the patients spontaneously reported having a paresthesia during nerve stimulation. However, on careful questioning, half of the patients (55%) reported electrical paresthesia, defined as dull tingling sensation traveling down to their hands and coinciding with the motor response. In addition, most patients (71%) spontaneously reported having a mild, radiating paresthesia on initial injection of local anesthetic. CONCLUSIONS: Painful paresthesiae should be infrequent when a low-stimulating current is used to identify the neural components of the brachial plexus and when the block needle is advanced slowly. Low-current intensity nerve stimulation can be used to achieve successful interscalene block with minimal discomfort to the patient.

Adult↗

Increased perception of post-ischemic paresthesias in depressed subjects.

A psychophysical assessment of sensory activity linked to unmyelinated and myelinated primary afferents was conducted by estimating the intensity of thermal and tactile post-ischemic paresthesias in 11 nontreated depressed subjects (Zung's index > or =50) and 19 controls. Blood flow in the dominant forearm was arrested until ischemic pain tolerance was reached. Ischemic pain and post-ischemic paresthesias were numerically rated. The duration of blood flow occlusion to the time of ischemic pain tolerance was similar in both groups. Thermal (warm/cool) and tactile (tingling) paresthesias were 96% and 57% more intense in depressed than in control subjects, respectively. Zung's depression scores were positively correlated with the tingling and thermal paresthesias. Ischemic pain intensity correlated positively with thermal paresthesias. These findings suggest that depression is associated with enhanced sensory paresthesias that are known to be predominately linked to unmyelinated afferent activity.

Adult↗

Infection-related mental and inferior alveolar nerve paresthesia: literature review and presentation of two cases.

A review of the literature on infection-related mental and inferior alveolar nerve paresthesia is given. This is followed by 2 case reports. The first case is of a mandibular left second molar in which a chloropercha overfill puff occurred in the vicinity of the inferior alveolar canal. The tooth remained asymptomatic until 2 and 1/2 yr later, when the periapical lesion enlarged and swelling, pain, and paresthesia developed. The paresthesia resolved 2 weeks following periapical surgery. The second case is of a mandibular right first premolar in which paresthesia began 1 day after the initial endodontic treatment. The intracanal medication was formocresol on a cotton pellet that was squeezed dry. The paresthesia was treated by irrigation, antibiotics, and dexamethasone. The paresthesia lasted 7 weeks, and when it resolved the root canal was filled with gutta-percha/eucapercha. Almost 9 months later, the tooth remained asymptomatic.

Bicuspid↗

Relationship between evoked motor response and sensory paresthesia in interscalene brachial plexus block.

BACKGROUND AND OBJECTIVES: This study sought to define the relationship between a paresthesia and a motor response (MR) to electrical nerve stimulation using a peripheral nerve stimulator (PNS) during interscalene block. We sought to determine if at a low amperage (< or =1.0 mA) a MR would precede a paresthesia. METHODS: Twenty-two interscalene blocks were performed using insulated needles and a PNS. A MR was obtained at 0.5 mA and then the PNS was turned off. The needle was further advanced until a paresthesia was elicited. The PNS was again turned on, the needle held immobile, and the amperage increased in 0.1 mA increments up to 0.5 mA, or an MR obtained, whichever occurred first. If no MR was obtained, the needle was withdrawn at 0.5 mA in the same direction as it entered until MR was again observed. RESULTS: A MR was obtained at 0.5 mA in all the patients. After the PNS was turned off and the needle further advanced, a paresthesia was elicited in 21 patients. When the PNS was turned on again, a MR was produced at 0 to 0.5 mA in 13 patients. In a subset of 8 patients without a second MR to stimulation up to 0.5 mA, the needle was withdrawn at that amperage. A MR was subsequently obtained during withdrawal in each patient in this subset. CONCLUSIONS: MR preceded paresthesia in every patient. The most likely explanation for this observation is that MR can be achieved at a small distance from the nerve, whereas elicitation of mechanical paresthesia requires either nerve contact or more intimate location of the needle's tip relative to the nerve. Another possible explanation is that motor fibers are located in a more superficial position and are therefore encountered first. Motor and sensory responses are separate and discrete phenomena.

Adult↗

[Changes of the distribution of sensory disturbances and paresthesiae after carpal tunnel release].

OBJECTIVES: Evaluation of changes of sensory disturbances, distribution of paresthesiae, and withdrawal of symptoms within 12 months after carpal tunnel release. PATIENTS AND METHODS: Thirty-nine patients with carpal tunnel syndrome (CTS) were evaluated for distribution of sensory disturbances. Two-point discrimination and filament testing were measured. The results were semi-quantitatively expressed as a sensory index. Distribution of paresthesiae were recorded on the whole hand, wrist and forearm. All patients completed the Levine questionnaire. Patients were assessed before the operation and at 3, 6 and 12 months after surgery. In all cases carpal tunnel was released by double incision open technique. RESULTS: Sensory index for two-point discrimination fell from initial value of 1.7 to 1.4 at 3 months, and to 1.2 at 6 months and 1 year. Index for filament testing decreased from initial 2.5 to 1.8 at 3 months, 1.5 at 6 months, and 1.7 at 1 year. Subjective patients' satisfaction measured by symptomatic part of the Levine questionnaire improved significantly within first 6 months after surgery. Paresthesiae were initially experienced on middle fingertip in 90% of patients, on index fingertip in 80% and on thumb/annular fingertips in 70%. More than 50% patients complained of these symptoms to be present on little finger and 20% on the dorsal aspect of the fingers/hand. At 3 months less than 30% of the patients experienced paresthesiae on fingertips I-IV and 15% on little fingertip. At 1 year, 10% of patients still complained of paresthesias on middle and little fingertips. CONCLUSIONS: Sensation improves statistically significantly within first 6 months after surgery, similarly to subjective patients' satisfaction assessed by the Levine questionnaire. Experience of paresthesiae in patients with CTS is not confined to the distribution of median nerve, although they are present most frequently at index and middle fingertips.

Adult↗