Radial Nerve Trunks Research Articles

Targeted Muscle Reinnervation in the Upper Arm: A Functional Anatomical Study

BackgroundThe aim of this study was to accurately locate the neural fascicle controlling hand movement in the upper arm, to enhance expression of motor intention after targeted muscle reinnervation. MethodsThe right sides of the median, ulnar and radial nerves were dissected from distal to proximal in 6 fresh cadaver specimens. The sectional location and diameter of the functional fascicle were measured at 10 and 20 cm below the acromion. The diameter of the main muscle branches of muscle reinnervation target muscles was measured. ResultsThe median nerve branch of finger and wrist flexion was mainly located between the 9 and 12 o’clock positions in the plane 10 and 20 cm below the acromion, where the diameter of the nerve fascicle was 2.07 and 2.04 mm, respectively. The ulnar nerve branch of finger and wrist flexion was mainly located between the 8 and 12 o’clock positions, with a diameter of respectively 1.80 and 1.99 mm. The radial branch of finger and wrist extension was mainly located between the 10 and 2 o’clock positions in the plane 10 cm below the acromion and between 6 and 12 o’clock in the plane 20 cm below the acromion, with a diameter of respectively 2.57 and 3.03 mm. ConclusionsThe nerve fascicles innervating the flexor and extensor fingers were distributed in relatively constant regions of the median, ulnar and radial nerve trunks, and their diameters closely matched the muscle branches of the target muscle.

A Temporal–Spatial Atlas of Peripheral Nerve Evoked Cortex Potential in Rat: A Novel Testbed to Explore the Responding Patterns of the Brain to Peripheral Nerves

Observing the dynamic progress of the brain in response to peripheral nerve stimulation as a whole is the basis for a deeper understanding of overall brain function; however, it remains a great challenge. In this work, a novel mini-invasive orthogonal recording method is developed to observe the overall evoked cortex potential (ECP) in rat brain. A typical ECP atlas with recognizable waveforms in the rat cortex corresponding to the median, ulnar, and radial nerve trunks and subdivided branches is acquired. Reproducible exciting temporal–spatial progress in the rat brain is obtained and visualized for the first time. Changes in the ECPs and exciting sequences in the cortex four months after median nerve transection are also observed. The results suggest that the brain’s response to peripheral stimulation has precise and reproducible temporal–spatial properties. This resource can serve as a testbed to explore the overall functional interaction and dynamic remodeling mechanisms between the peripheral and central nervous systems over time.

Effects of neurodynamic interventions on pain sensitivity and function in patients with multiple sclerosis: a randomized clinical trial

ObjectiveTo assess the effects of adding a neurodynamic intervention into a multimodal management approach in individuals with multiple sclerosis (MS) with upper extremity pain symptoms. DesignRandomized clinical trial. SettingTertiary hospital center. ParticipantsThirty-two individuals with MS were randomly assigned to multimodal usual care alone (n=16) or multimodal usual care plus neurodynamic intervention (n=16). InterventionsBoth groups received 5 sessions of multimodal usual care of 30minutes duration, twice per week. Subjects allocated to the neurodynamic group also received bilateral neurodynamic slider interventions targeting the upper extremity nerve trunks. Outcome measuresPressure pain thresholds (PPTs) at the radial, median and ulnar nerve trunks, second metacarpal and tibialis anterior, pain intensity in the upper extremity (NPRS, 0–10), light touch detection threshold (von Frey hairs) and manual dexterity (nine-hole peg test) were assessed before and after the intervention. ResultsSubjects receiving the neurodynamic interventions experienced larger improvements in PPTs at all locations (moderate effect size, between-groups differences from 89.5 to 186.5kPa), a higher decrease in pain intensity at rest (large effect, difference 1.7, 95%CI 0.4 to 3.0) and improvements in sensitivity to light touch (moderate effect, difference −0.7, 95%CI −1.3 to −0.1) and in manual dexterity (large effect, difference 7.7, 95%CI 4.0 to 11.4seconds) than those that did not receive the neurodynamic intervention. ConclusionsThe inclusion of neural mobilization into a multimodal management approach resulted in reduction of pressure sensitivity, greater reduction in pain and improvement in sensitivity to light touch and manual dexterity in MS. Further studies are necessary to confirm these findings at longer term follow-ups. (ClinicalTrials.gov: NCT03595631)

Mathematical Modeling for Neuropathic Pain: Bayesian Linear Regression and Self-Organizing Maps Applied to Carpal Tunnel Syndrome

A better understanding of the connection between risk factors associated with pain and function may assist therapists in optimizing therapeutic programs. This study applied mathematical modeling to analyze the relationship of psychological, psychophysical, and motor variables with pain, function, and symptom severity using Bayesian linear regressions (BLR) and self-organizing maps (SOMs) in carpal tunnel syndrome (CTS). The novelty of this work was a transfer of the symmetry mathematical background to a neuropathic pain condition, whose symptoms can be either unilateral or bilateral. Duration of symptoms, pain intensity, function, symptom severity, depressive levels, pinch tip grip force, and pressure pain thresholds (PPTs) over the ulnar, radial, and median nerve trunks, the cervical spine, the carpal tunnel, and the tibialis anterior were collected in 208 women suffering from CTS. The first BLR model revealed that symptom severity, PPTs over the radial nerve, and function had significant correlations with pain intensity. The second BLR showed that symptom severity, depressive levels, pain intensity, and years with pain were associated with function. The third model demonstrated that pain intensity and function were associated with symptom severity. The SOMs visualized these correlations among variables, i.e., clinical, psychophysical, and physical, and identified a subgroup of women with CTS exhibiting worse clinical features, higher pressure sensitivity, and lower pinch tip grip force. Therefore, the application of mathematical modeling identified some interactions among the intensity of pain, function, and symptom severity in women with CTS.

Widespread Pressure Pain Hypersensitivity in Musculoskeletal and Nerve Trunk Areas as a Sign of Altered Nociceptive Processing in Unilateral Plantar Heel Pain

Our aim was to investigate the differences in pressure sensitivity over musculoskeletal and nerve symptomatic and distant areas between individuals with plantar heel pain and healthy subjects and to determine the relationship between sensitivity to pressure pain, foot pain, and fascia thickness. Thirty-five patients with unilateral chronic plantar heel pain and 35 matched healthy controls participated. Pressure pain thresholds (PPTs) were assessed bilaterally over several nerve trunks (median, radial, ulnar, common peroneal, tibial, and sural nerve trunks) and musculoskeletal structures (calcaneus, medial gastrocnemius, tibialis anterior, and second metacarpal) by an assessor blinded to the subject's condition. Pain was assessed with a numerical pain rating scale (0–10), impact of foot pain was assessed with the Foot Function Index, and plantar fascia thickness was measured via ultrasound imaging. Analysis of covariance revealed lower widespread and bilateral PPTs over both nerve trunks and musculoskeletal structures in individuals with plantar heel pain (P < .001). Female patients showed lower PPT than male patients in almost all points (P < .001). PPT over the peripheral nerve trunks of the lower extremity were significantly associated with the intensity of pain at first step in the morning and with the foot function disability scale of the Foot Function Index (P < .05). This study found widespread pressure pain hypersensitivity over both nerve trunks and musculoskeletal structures in individuals with unilateral chronic plantar heel pain, suggesting the presence of a central altered central nociceptive pain processing. Pressure hypersensitivity over nerve trunks on the lower extremity was associated with higher pain intensity and related disability. PerspectivesThis study found widespread pressure hypersensitivity over both nerve trunks and musculoskeletal structures in individuals with unilateral chronic plantar heel pain, as a manifestation of a centrally altered central nociceptive pain processing.

Posterior interosseous neuropathy: Supinator syndrome vs fascicular radial neuropathy.

Objective:To investigate the spatial pattern of lesion dispersion in posterior interosseous neuropathy syndrome (PINS) by high-resolution magnetic resonance neurography.Methods:This prospective study was approved by the local ethics committee and written informed consent was obtained from all patients. In 19 patients with PINS and 20 healthy controls, a standardized magnetic resonance neurography protocol at 3-tesla was performed with coverage of the upper arm and elbow (T2-weighted fat-saturated: echo time/repetition time 52/7,020 milliseconds, in-plane resolution 0.27 × 0.27 mm2). Lesion classification of the radial nerve trunk and its deep branch (which becomes the posterior interosseous nerve) was performed by visual rating and additional quantitative analysis of normalized T2 signal of radial nerve voxels.Results:Of 19 patients with PINS, only 3 (16%) had a focal neuropathy at the entry of the radial nerve deep branch into the supinator muscle at elbow/forearm level. The other 16 (84%) had proximal radial nerve lesions at the upper arm level with a predominant lesion focus 8.3 ± 4.6 cm proximal to the humeroradial joint. Most of these lesions (75%) followed a specific somatotopic pattern, involving only those fascicles that would form the posterior interosseous nerve more distally.Conclusions:PINS is not necessarily caused by focal compression at the supinator muscle but is instead frequently a consequence of partial fascicular lesions of the radial nerve trunk at the upper arm level. Neuroimaging should be considered as a complementary diagnostic method in PINS.

Widespread Pressure Pain Hypersensitivity in Patients With Multiple Sclerosis With and Without Pain as Sign of Central Sensitization

To determine the presence of widespread pressure hyperalgesia in multiple sclerosis (MS) patients with and without pain and its association with pain and fatigue. A total of 108 individuals with definite MS, 49 men and 59 women (mean age, 44±8 y) and 108 age-matched and sex-matched pain-free controls (mean age, 44±9 y) were included. Fifty patients (n=58, 54%) reported pain and 50 (46%) did not. Pressure pain threshold (PPT) was bilaterally assessed over supraorbital, infraorbital, mental, median, radial and ulnar nerve trunks, C5-C6 joint, second metacarpal, and tibialis anterior muscle by an assessor blinded to the patient's condition. The intensity of pain was assessed with a numerical pain rate scale (0 to 10), fatigue was determined with the Fatigue Impact Scale, and depression was evaluated with the Beck Depression Inventory. The analyses of covariance revealed that PPT were significantly decreased bilaterally over the supraorbital, infraorbital, mental, median, ulnar and radial nerve trunks, C5-C6 joint, second metacarpal, and tibialis anterior muscles in patients with MS compared with pain-free controls (all, P<0.001). No significant differences existed between MS patients with pain and those without pain (all P>0.944). Patients with pain exhibited higher fatigue and depression than those patients without pain (P<0.05). PPT was not associated with any clinical variable, that is, pain, depression, or fatigue. Our study found widespread pressure pain hyperalgesia in individuals with MS as compared with pain-free controls. No differences existed between MS patients with pain and those without pain in the presence of widespread pressure sensitivity. Current results suggest that MS is associated with sensory hyperexcitability of the central nervous system or dysfunction in endogenous pain modulatory systems.

Nerve pressure pain hypersensitivity and upper limb mechanosensitivity in breast cancer survivors: a case-control study.

This study aims to investigate the presence of bilateral pressure pain hypersensitivity in arm trunk nerves and upper limb mechanosensitivity in breast cancer patients with neck-shoulder pain after medical treatments. Twenty-two breast cancer survivors (mean age 49.05 ± 7.8 years) and matched healthy controls (mean age 50.76 ± 7.6 years) participated in the study. Neck and shoulder pain was evaluated using an 11-point numerical point rating scale. Pressure pain thresholds (PPTs) were bilaterally assessed over the median, radial, and ulnar nerve trunks and tibialis muscle, and the neurodynamics of the upper limb by neural tolerance to movement was evaluated in the median, radial, and ulnar nerves. Thirteen (59.1%) patients reported spontaneous neck pain, and 16 (72.7%) patients showed spontaneous shoulder/axillary pain. Analysis of variance revealed that breast cancer survivors showed significant between-group but not between-side differences over the median nerve trunk (group: P = < 0.001; side: P = 0.146), radial nerve trunk (group: P = < 0.001; side: P = 0.300), ulnar nerve trunk (group: P = < 0.001; side: P = 0.744), and tibialis anterior muscle (group: P = < 0.001; side: P = 0.118). The patients also showed statistically significant differences in range of motion (ROM) between groups and between sides in ULNT1(MEDIAN)(group: P = < 0.001; side: P = < 0.001) and ULNT(ULNAR) (group: P = 0.009; side: P = 0.002). The analysis did not show statistically significant differences in ROM between groups, but there was a statistical significance between sides for ULNT(RADIAL) (group: P = 0.081; side: P = 0.046). Breast cancer survivors present bilateral and widespread neural hypersensitivity, as they did in muscular tissue in previous studies. Breast cancer survivors demonstrate a reduction in ROM during ULNTs in the affected side.

Innocuous Peripheral Nerve Stimulation Shifts Stimulus–Response Function of Painful Laser Stimulation in Man

Electrical peripheral nerve stimulation (PNS) is discussed as an effective neuromodulatory treatment in chronic pain. This human experimental study hypothesized a rightward shift of stimulus-response function as a marker of antinociceptive and analgesic PNS effects. Innocuous electrical PNS of the left superficial radial nerve trunk evoked paresthesia on the left hand dorsum in 29 healthy volunteers. In this innervation area, laser stimulation was performed before, during, and after PNS. Ten different laser intensities ranging between perception and tolerance thresholds were applied. Cortical laser-evoked potentials (LEP) were recorded, and perceptual ratings were documented. Data were analyzed in low, medium, and high laser intensity categories. Stimulus-response functions were calculated. Laser detection and pain thresholds were interpolated. Interpolated laser thresholds after logarithmic regression were not different from measured thresholds. Laser pain threshold increased during and after PNS. LEP amplitude decreased at medium and high intensities under PNS. Ratings transiently decreased during PNS at medium and high laser intensities. Modulation of laser pain threshold, perceptual ratings, and LEP indicates a rightward shift of stimulus-response function under PNS. These data emphasize antinociceptive and analgesic effects of PNS in an experimental human model and support its clinical neuromodulative relevance.

Catechol-O-Methyltransferase Val158Met Polymorphism is Associated with Pain and Disability, but not Widespread Pressure Pain Sensitivity, in Women with Carpal Tunnel Syndrome

Background: The genetic influence of Val158Met polymorphisms, one of the potential genetic determinants for nociceptive processing, has not been previously investigated in women with carpal tunnel syndrome (CTS). Objectives: To investigate the association between the Val158Met polymorphism with CTS and to assess the relationship between the Val158Met polymorphism and the clinical outcomes and widespread pressure pain hypersensitivity in women with CTS. Study Design: Case control study. Setting: Neurology department at an urban hospital. Method: One hundred nine (n = 109) women (mean age: 47 ± 9 years) with a clinical and electrodiagnostic diagnosis of CTS and 109 matched healthy women participated. After amplifying the Val158Met polymorphism by polymerase chain reactions, rs4680 genotype frequencies and allele distributions were calculated. We classified individuals according to their Val158Met polymorphism: Val/Val, Val/Met, Met/Met. The intensity of the pain was assessed with a numeric rating scale (0-10) and disability was determined with the Boston Carpal Tunnel Questionnaire. Pressure pain thresholds were bilaterally assessed over median, radial, and ulnar nerve trunks; C5-C6 facet joints; and carpal tunnel and tibialis anterior muscles. Institutional Review Board: The study project was approved by the local human research committee (HUFA-12/14). All participants signed an informed consent prior to their inclusion in the study. Results: The distribution of the 3 Val158Met genotypes (Val/Val, Val/Met, Met/Met) and alleles was not significantly different between women with CTS and healthy women (χ2 = 0.498; P = 0.780). Women with CTS carrying the Met/Met genotype showed higher levels of pain and disability than those with the Val/Met genotype (P &lt; 0.01) and with the Val/Val genotype (P &lt; 0.001). No differences in the years with pain (P = 0.954), age (P = 0.740), depression (P = 0.530), severity of CTS (P = 0.744) or presence of unilateral-bilateral symptoms (P = 0.279) existed depending on the rs4680 Val158Met genotype. No significant differences in widespread pressure pain sensitivity were observed in any of the points depending on the rs4680 Val158Met genotype (P &gt; 0.315). Limitations: We only recruited women from a specialized department. Conclusion: Current results indicated that the Val158Met polymorphism seems not to be a risk factor for the development of CTS; however, it was associated with increased perception of pain and higher disability scores. Key words: Catechol-O-methyltransferase gene, carpal tunnel syndrome, polymorphism pressure pain thresholds, sensitivity.

Increased Pain Sensitivity Is Not Associated With Electrodiagnostic Findings in Women With Carpal Tunnel Syndrome

To determine the differences in widespread pressure pain and thermal hypersensitivity in women with minimal, moderate, and severe carpal tunnel syndrome (CTS) and healthy controls. A total of 72 women with CTS (19 with minimal, 18 with moderate, and 35 with severe) and 19 healthy age-matched women participated. Pressure pain thresholds were bilaterally assessed over the median, ulnar, and radial nerves, the C5 to C6 zygapophyseal joint, the carpal tunnel, and the tibialis anterior muscle. In addition, warm and cold detection thresholds and heat and cold pain thresholds were bilaterally assessed over the carpal tunnel and the thenar eminence. All outcome parameters were assessed by an assessor blinded to the participant's condition. No significant differences in pain parameters among patients with minimal, moderate, and severe CTS were found. The results showed that PPT were significantly decreased bilaterally over the median, ulnar, and radial nerve trunks, the carpal tunnel, C5 to C6 zygapophyseal joint, and the tibialis anterior muscle in patients with minimal, moderate, or severe CTS as compared with healthy controls (all, P<0.001). In addition, patients with CTS also showed lower heat pain threshold and reduced cold pain threshold compared with controls (P<0.001). No significant sensory differences between minimal, moderate, or severe CTS were found. The similar widespread pressure and thermal hypersensitivity in patients with minimal, moderate, or severe CTS and pain intensity suggests that increased pain sensitivity is not related to electrodiagnostic findings.

Selective Neurotization of the Radial Nerve in the Axilla Using a Full-Length Phrenic Nerve to Treat Complete Brachial Plexus Palsy: An Anatomic Study and Case Report

Current methods for the restoration of wrist and digit extension after a complete brachial plexus injury result in poor outcomes. To determine the internal topography of the radial nerve in the axilla and present a method for selective neurotization of the radial nerve using a full-length phrenic nerve. Internal topographic features of the fascicular groups of the radial nerve were observed at the level of latissimus dorsi insertion in 16 cadavers. Selective neurotization of the medial portion of the antebrachial part of the main trunk of the radial nerve was performed at this level using a full-length phrenic nerve in one patient with complete brachial plexus palsy. At the level of latissimus dorsi insertion in the axilla, the antebrachial part of the radial nerve, which innervates the forearm extensors, is located at the superior lateral part of the radial nerve trunk. It can be divided into medial and lateral portions. Transfer of a full-length phrenic nerve was used to selectively reinnervate the medial portion of the antebrachial part of the radial nerve in 1 patient with complete brachial plexus palsy. The patient's antebrachial extensor muscles regained Grade 4 power when assessed 3 years after surgery. The fibers that innervate the antebrachial extensors are located at the superior lateral part of the radial nerve trunk in the axilla. Selective neurotization of the radial nerve at this level with a phrenic nerve was performed successfully in 1 patient.

Specific Mechanical Pain Hypersensitivity Over Peripheral Nerve Trunks in Women With Either Unilateral Epicondylalgia or Carpal Tunnel Syndrome

Case-control study with blinded examiner. To investigate if pressure pain sensitivity is related to specific nerve trunks in the upper extremity of patients with either unilateral lateral epicondylalgia (LE) or carpal tunnel syndrome (CTS). In the clinical setting, patients with LE tend to exhibit radial nerve trunk tenderness, whereas patients with CTS exhibit median nerve tenderness. No studies have investigated if specific nerve pressure pain hypersensitivity exists in patients with either LE or CTS. Sixteen women with unilateral LE (mean±SD age, 43±7 years), 17 women with unilateral CTS (43±6 years), and 17 healthy women (43±6 years) were included in this study. Pressure pain thresholds (PPT) were bilaterally assessed over the median, ulnar, and radial nerve trunks, as well as over the C5-6 zygapophyseal joints, by an examiner blinded to the subjectsí condition. A mixed-model analysis of variance was used to evaluate differences in PPT among groups (LE, CTS, or controls) and between sides (affected/nonaffected or dominant/nondominant). The individuals in both the LE and CTS groups demonstrated lower PPT bilaterally over the median (group, P<.001; side, P=.437), radial (group, P<.001; side, P=.556), and ulnar (group, P<.001; side, P=.938) nerve trunks as compared to controls. Additionally, radial (P<.001) and ulnar (P=.005) nerves were more sensitive bilaterally in patients with LE than in patients with CTS. The median nerve was more sensitive bilaterally in patients with CTS than patients with LE (P=.002). Lower PPT over the cervical spine (group, P<.001; side, P=.233) were found bilaterally in both the LE and CTS groups. Further, patients with CTS exhibited lower cervical PPT than patients with LE (P<.001). PPT was negatively correlated with both pain intensity and duration of symptoms in both the LE and CTS groups (P<.001). Bilateral mechanical nerve pain hypersensitivity is related to specific and particular nerve trunks in women with either unilateral LE or CTS. Our results suggest the presence of central and peripheral sensitization mechanisms in individuals with either LE or CTS.

Widespread Mechanical Pain Hypersensitivity as Sign of Central Sensitization in Unilateral Epicondylalgia

The aim of this study was to investigate whether generalized deep tissue hyperalgesia exists in patients with chronic unilateral lateral epicondylalgia (LE). A total of 26 LE patients (10 males and 16 females, aged 25 to 63 y) and 20 healthy comparable matched controls (aged 26 to 61 y) were recruited and pressure pain threshold (PPT) was assessed bilaterally over the median, ulnar, and radial nerve trunks, the lateral epicondyle, C5-C6 zygapophyseal joint, and the tibialis anterior muscle in a blind design. PPT was significantly decreased bilaterally over the median, ulnar, and radial nerve trunks, the lateral epicondyle, the C5-C6 zygapophyseal joint, and tibialis anterior muscle in patients with LE than healthy controls (all P<0.001). PPTs over those measured points was negatively related to current elbow pain intensity (all P<0.05). A more significant decrease in PPTs were present in females (all P<0.05). This revealed a widespread mechanical hypersensitivity in patients with LE, which suggest that central sensitization mechanisms are involved in patients with unilateral LE. The generalized decrease in PPT levels was associated with elbow pain intensity, supporting a role of peripheral sensitization mechanisms in the initiation or maintenance of central sensitization mechanisms. In addition, females may be more prone to the development of generalized mechanical hypersensitivity.

Bilateral Widespread Mechanical Pain Sensitivity in Women With Myofascial Temporomandibular Disorder: Evidence of Impairment in Central Nociceptive Processing

Our aim was to investigate bilateral, widespread pressure-pain hypersensitivity in nerve, muscle, and joint tissues in women with myofascial temporomandibular disorders (TMD) without concomitant comorbid conditions. Twenty women with myofascial TMD (aged 20 to 28 years old), and 20 healthy matched women (aged 20 to 29 years), were recruited. Pressure-pain thresholds (PPT) were bilaterally assessed over supra-orbital (V1), infra-orbital (V2), mental (V3) nerves, median (C5), radial (C6) and ulnar (C7) nerve trunks, the C5-C6 zygapophyseal joint, the lateral pole of the temporo mandibular joint (TMJ), and the tibialis anterior muscle in a blinded design. The results showed that PPTs were significantly decreased bilaterally over the supra-orbital, infra-orbital, and mental nerves, median, ulnar, and radial nerve trunks, the lateral pole of the TMJ, the C5-C6 zygapophyseal joint, and the tibialis anterior muscle in patients with myofascial TMD as compared to healthy controls (all sites: P < .001). There were no significant differences in the magnitude of PPT decreases between the trigeminal and extratrigeminal test sites. PPT over the mental nerve, the TMJ, C5-C6 zygapophyseal joint and tibialis anterior muscle were negatively correlated to both duration of pain symptoms and TMD pain intensity (P < .05). Our findings revealed bilateral, widespread pressure hypersensitivity in women presenting with myofascial TMD, suggesting that widespread central sensitization is involved in myofascial TMD women. This article reveals the presence of bilateral and widespread pressure-pain hypersensitivity in women with myofascial TMD, suggesting that widespread central sensitization is involved in myofascial TMD. This finding has implications for development of management strategies.

Bilateral widespread mechanical pain sensitivity in carpal tunnel syndrome: evidence of central processing in unilateral neuropathy

The aim of this study was to investigate whether bilateral widespread pressure hypersensitivity exists in patients with unilateral carpal tunnel syndrome. A total of 20 females with carpal tunnel syndrome (aged 22-60 years), and 20 healthy matched females (aged 21-60 years old) were recruited. Pressure pain thresholds were assessed bilaterally over median, ulnar, and radial nerve trunks, the C5-C6 zygapophyseal joint, the carpal tunnel and the tibialis anterior muscle in a blinded design. The results showed that pressure pain threshold levels were significantly decreased bilaterally over the median, ulnar, and radial nerve trunks, the carpal tunnel, the C5-C6 zygapophyseal joint, and the tibialis anterior muscle in patients with unilateral carpal tunnel syndrome as compared to healthy controls (all, P < 0.001). Pressure pain threshold was negatively correlated to both hand pain intensity and duration of symptoms (all, P < 0.001). Our findings revealed bilateral widespread pressure hypersensitivity in subjects with carpal tunnel syndrome, which suggest that widespread central sensitization is involved in patients with unilateral carpal tunnel syndrome. The generalized decrease in pressure pain thresholds associated with pain intensity and duration of symptoms supports a role of the peripheral drive to initiate and maintain central sensitization. Nevertheless, both central and peripheral sensitization mechanisms are probably involved at the same time in carpal tunnel syndrome.

Tardy radial nerve palsy caused by pseudoarthrosis of humeral shaft

1. IntroductionBecause of its close proximity, the radial nerve can be injuredwhen a displaced fracture of the humeral shaft occurs. Delayedradial nerve palsy is very rare. However, we report a case in whichthepalsypresentedmorethan3yearsafterthefirstoperation,andwas due to chronic entrapment of the radial nerve by thedevelopment of fibrous tissue.2. Case reportA 24-year-old man was involved in a high-speed motor vehicleaccident, and sustained a closed mid-shaft fracture of the righthumerus (AO/ASIF classification type B2: Fig. 1). Fixation wasperformed 3 days after injury, using an antegrade intramedullarynail and Russell–Taylor device (R–T: Smith & Nephew, Memphis,MO, USA). Postoperative hypoaesthesia of the radial nerve regionnoted, but this resolved within 1 month. At 10 months post-operativelythefracturestillshowednon-union,butthemancouldnot attend our hospital because of the demands of his job.However,3yearsand 4monthsafter theoperation heexperiencedacute-onset paresis and hypoaesthesia (5/10) in the area suppliedby the radial nerve, with decreased wrist strength and fingerextension (MMT level 2) while he was playing the drums as ahobby. The nerve percussion test was positive in the left posteriorregion of the humerus. On radiography, the fracture site showedpseudoarthrosis with incomplete callus (Fig. 2). A nerve conduc-tion study revealed conduction block of the radial nerve at theposterolateral part of the callus (Fig. 3). Scintigraphy showed a hotregion on the right humeral stem (Fig. 4). A diagnosis was made oftardy radial nerve palsy caused by pseudoarthrosis of the righthumeral shaft fracture.Thesymptomshadnotimprovedby6weeksafteronsetdespiteconservative treatment, and a second operation was carried out.The radial nerve trunk was found to be compressed by fibroustissue at the callus site. The R–T was removed and bone graftingwith decompression of the radial nerve was performed, followedby replantation using an unreamed humeral nail (Synthes,Bettlach, Switzerland). At 4 weeks after this procedure, thesymptoms had improved. Nerve conduction had recoveredcompletely at 6 months (Fig. 3) and, at 18 months, the fractureshowedunion.Thedevicewasremovedat24monthsfollowingthesecond operation (Fig. 4). At the last follow-up examination at 42months, the man had no complaints, showed full range of motionof the shoulder and elbow with no neurological defects and couldwork unhindered.3. DiscussionConservative treatment is the first choice for humeral shaftfracture. However, pseudoarthrosis sometimes develops in trans-verse or short spiral fractures,so that recentlymore stable fixationusinganintramedullary nailhas been favoured.Radial nerve palsycan occur in 2–18% of humeral shaft fractures, but neurotmesis, orentrapment of the nerve trunk, occurs in only 5% of cases withoutopen fracture. Hence conservative treatment is favoured.

Anatomical features of radial nerve in the elbow and forearm

Objective To observe the anatomical features of radial nerve in the elbow and forearm and apply the anatomical data in surgical nerve repair. Methods Thirty-six adult cadaver arms were carefully dissected. The elbow part of radial nerve was identified from the space between brachial muscle and brachioradialis muscle via an S shape incision at the lateral side of the elbow. The deep branch of the radial nerve distal to its supinator muscle exit was traced distally to explore and identify all the muscular branches. The length of the muscular branches and the distance of the take off and muscle entry point of these branches to the epicondyle of the humerus were measured. Retrograde dissection of the muscular branched was also done to locate the distribution of these branches in the radial nerve proper at the level of epicondyle. Twelve cases of radial nerve injury at the elbow were treated with either oriented repair or non-oriented repair. Recovery of muscle power of deep radial nerve innervated muscles was measured and the effective recovery rates were compared between the group of oriented nerve repair and non-oriented repair. Results The motor nerve fibers lied in the medial portion of the radial nerve trunk. Extensor pollicis longus was the distal most muscle innervated by radial nerve deep branch. The average follow-up time of the 12 cases was 2.4 year. The effective rate of the group (n=6) with oriented nerve repair was 83.3% while that of the group (n=6) of non-oriented nerve repair was 50.0%. Conclusion The diagnosis of posterior interosseous nerve injury must been considered when patients complain about difficulty in thumb extension following blunt injury to the dorsolateral forearm in the level 10 to 15cm to the lateral epicondyle. Based on the distribution radial nerve motor fibers. the medial portion of the radial nerve trunk should be carefully reapproximated with microsurgical repair. Key words: Radial nerve; Neuroanatomy; Forearm; Clinical research

Analgesic and antinociceptive effects of peripheral nerve neurostimulation in an advanced human experimental model

Electrical peripheral nerve neurostimulation (PNS) is reported to be an effective pain treatment. An objective proof of antinociceptive effect is lacking. The human experimental study addressed PNS effects on nociception and pain by electrophysiology and psychophysics. In 23 healthy volunteers, 39 sessions were conducted. Three experiments (PNS ipsilateral, PNS contralateral, Control) consisted of 13 sessions each. Conditioning PNS (100 Hz) of left (PNS ipsilateral) or right (PNS contralateral) superficial radial nerve trunk evoked non-painful, tingling sensations on the hand dorsum. Local cutaneous anesthesia at PNS site provided for preferential nerve trunk stimulation. Cortical laser-evoked potentials (LEP) after painful stimulation at left hand dorsum were recorded together with mechanical and thermal perception thresholds at the same site before ( T1), during ( T2), and after ( T3) PNS or a no stimulation period (Control). Mechanical and thermal perception decreased in the anesthetized area. Late LEP amplitude decreased independently of PNS site. Exclusively under ipsilateral PNS, N2 latency increased and laser ratings decreased. Mechanical detection threshold transiently increased during ipsilateral PNS at hand dorsum. PNS induced strong reduction of mechanical perception due to peripheral collision of orthodromic (test stimulus) and antidromic (PNS) selective Aβ fiber excitation. Delay of N2 component and reduction of laser pain were specific to ipsilateral PNS. Divergent and common effects of ipsilateral and contralateral PNS suggest a combination of peripheral and central antinociceptive mechanisms. The study in man documents inhibition of nociception and pain by PNS and provides with an experimental model for future objectives in neuromodulation.

Widespread Sensory Hypersensitivity Is a Feature of Chronic Whiplash-Associated Disorder but not Chronic Idiopathic Neck Pain

To investigate sensory changes present in patients with chronic whiplash-associated disorders and chronic idiopathic neck pain using a variety of quantitative sensory tests to better understand the pain processing mechanisms underlying persistent symptoms. A case control study was used with 29 subjects with chronic whiplash-associated disorders, 20 subjects with chronic idiopathic neck pain, and 20 pain-free volunteers. Pressure pain thresholds were measured over the articular pillars of C2-C3, C5-C6, the median, radial, and ulnar nerve trunks in the arm and over a remote site, the muscle belly of tibialis anterior. Heat pain thresholds, cold pain thresholds, and von Frey hair sensibility were measured over the cervical spine, tibialis anterior, and deltoid insertion. Anxiety was measured with the Short-Form of the Spielberger State Anxiety Inventory. Pressure pain thresholds were decreased over cervical spine sites in both subject groups when compared with controls (P < 0.05). In the chronic whiplash-associated disorders group, pressure pain thresholds were also decreased over the tibialis anterior, median, and radial nerve trunks (P < 0.001). Heat pain thresholds were decreased and cold pain thresholds increased at all sites (P < 0.03). No differences in heat pain thresholds or cold pain thresholds were evident in the idiopathic neck pain group at any site compared with the control group (P > 0.27). No abnormalities in von Frey hair sensibility were evident in either neck pain group (P > 0.28). Both chronic whiplash-associated disorders and idiopathic neck pain groups were characterized by mechanical hyperalgesia over the cervical spine. Whiplash subjects showed additional widespread hypersensitivity to mechanical pressure and thermal stimuli, which was independent of state anxiety and may represent changes in central pain processing mechanisms. This may have implications for future treatment approaches.