Mixed Nerve Research Articles

Etiology of Carpal Tunnel Syndrome in a Large Cohort of Children.

(1) Background: Carpal tunnel syndrome (CTS), a compressive mononeuropathy of the median nerve at the wrist, is rare in childhood and occurs most frequently due to secondary causes. (2) Methods: Medical history, electrodiagnostic findings, and imaging data of patients with CTS from two pediatric neuromuscular centers were analyzed retrospectively. The etiology of CTS was investigated and compared with the literature. (3) Results: We report on a cohort of 38 CTS patients (n = 22 females, n = 29 bilateral, mean age at diagnosis 9.8 years). Electrodiagnostic studies of all patients revealed slowing of the antidromic sensory or orthodromic mixed nerve conduction velocities across the carpal tunnel or lack of the sensory nerve action potential and/or prolonged distal motor latencies. Median nerve ultrasound was diagnostic for CTS and confirmed tumorous and vascular malformations. Etiology was secondary in most patients (n = 29; 76%), and mucopolysaccharidosis was the most frequent underlying condition (n = 14; 37%). Idiopathic CTS was rare in this pediatric cohort (n = 9; 24%). (4) Conclusion: Since CTS in childhood is predominantly caused by an underlying disorder, a thorough evaluation and search for a causative condition is recommended in this age group.

Mapping Renal Innervations by Renal Nerve Stimulation and Characterizations of Blood Pressure Response Patterns.

Increased sympathetic nervous activity is one of main contributors to pathogenesis and progression of hypertension. Renal denervation (RDN) has been demonstrated as a potential therapy for treatment of hypertension; however, lack of indicators of intra-/post-procedure results in inconsistent clinical outcomes. Renal nerve stimulation (RNS), a simple and promising method, could evoke elevated blood pressure as an intraoperative indicator for RDN. But related researches on patterns of blood pressure responses to RNS are still incomplete. To investigate and categorize the phenotypes of blood pressure response to RNS and heart rate alteration before and after RNS, 24 Chinese Kunming dogs were used to perform RNS from bifurcation to ostium of renal arteries after angiography, and a total of 483 stimulated sites were complete. We identified five different patterns of blood pressure response to RNS in 483 stimulated sites, (1) continuous ascending and finally keeping steady above baseline (26.9%), (2) declining and then rising over baseline (11.8%), (3) declining and then rising but below baseline (14.5%), (4) fluctuating in the vicinity of baseline (39.5%), and (5) continuous declining and finally keeping steady below baseline (7.2%), and found no difference in RR intervals among five blood pressure responses before and after renal nerve stimulation. Renal nerve stimulation could elicit different patterns of blood pressure response, which could potentially assist in distinguishing sympathetic-excitatory sites and sympathetic-inhibitory sites from mixed nerve components, which might help to improve the efficacy of RDN.

A systematic review and meta-analysis of studies comparing muscle-in-vein conduits with autologous nerve grafts for nerve reconstruction

The gold-standard method for reconstruction of segmental nerve defects, the autologous nerve graft, has several drawbacks in terms of tissue availability and donor site morbidity. Therefore, feasible alternatives to autologous nerve grafts are sought. Muscle-in-vein conduits have been proposed as an alternative to autologous nerve grafts almost three decades ago, given the abundance of both tissues throughout the body. Based on the anti-inflammatory effects of veins and the proregenerative environment established by muscle tissue, this approach has been studied in various preclinical and some clinical trials. There is still no comprehensive systematic summary to conclude efficacy and feasibility of muscle-in-vein conduits for reconstruction of segmental nerve defects. Given this lack of a conclusive summary, we performed a meta-analysis to evaluate the potential of muscle-in-vein conduits. This work’s main findings are profound discrepancies regarding the results following nerve repair by means of muscle-in-vein conduits in a preclinical or clinical setting. We identified differences in study methodology, inter-species neurobiology and the limited number of clinical studies to be the main reasons for the still inconclusive results. In conclusion, we advise for large animal studies to elucidate the feasibility of muscle-in-vein conduits for repair of segmental defects of critical size in mixed nerves.

Total Denervation of the Elbow: Cadaveric Feasibility Study

Total elbow arthroplasty for the treatment of patients with severe elbow osteoarthritis is associated with postoperative activity limitations and risk of midterm complications. Elbow denervation could be an attractive therapeutic option for young, active patients. The aim of our study was to assess the feasibility of selective total elbow denervation via 2 anteriorly based approaches. Selective total elbow denervation was performed in 14 cadaver elbows by 2 fellowship-trained elbow surgeons. Lateral and medial approaches to the elbow were used. The length of skin incisions and the minimum distance between them were noted. The number of articular branches identified and their respective distances from the lateral or medial epicondyle of the humerus were recorded. The anterolateral and anteromedial approaches allowed for the identification of all mixed and sensory nerves in all 14 cases. The mean number of resultant articular branches per cadaver was 1 for the musculocutaneous nerve, 2 (range, 1-3) for the radial nerve, 1 (range, 1-3) for the posterior cutaneous nerve of the forearm, 2 (range, 1-3) for the ulnar nerve, and 2 (range, 1-3) for the medial antebrachial cutaneous nerve; the collateral ulnar nerve was connected directly to the capsule. The length of the medial and lateral incisions was 15 cm (range, 12-18 cm) and 12 cm (range, 10-16 cm), respectively. The mean minimum distance between the incisions was 7.5 cm (range, 6.7-8.5 cm). The findings suggest that selective elbow denervation via 2 approaches is feasible. Selective elbow denervation via 2 approaches is feasible. Surgeons should target the articular branches of the musculocutaneous, radial, ulnar, and collateral ulnar nerves, posterior cutaneous nerve of the forearm, as well as medial antebrachial cutaneous nerves when carrying out this procedure.

An Exploration of the Sympathetic Component of the Right Phrenic Nerve

Introduction The phrenic nerve is a mixed nerve that arises from the anterior primary rami of C3-C5 bilaterally and is the main motor supply to the diaphragm. The diaphragm muscle has a multifaceted impact on body functions- including breathing, visceral health, CSF flow, and emotional regulation. According to anatomical textbooks, the phrenic nerve receives catecholaminergic fibers from the middle and lower cervical ganglia. However, previous studies reveal that both phrenic nerves lack the sympathetic component at the diaphragm level, recovering it in the abdominal region supposedly from communication with a celiac plexus. Thus, the aim of the current study was to analyze the constitution of the supradiaphragmatic and abdominal divisions of the right phrenic nerve, targeting the presence of sympathetic fibers. Methods Six formalin-preserved adult human cadavers were dissected at the MSSU human dissection laboratory. The anatomical course of the supra and subdiaphragmatic portions of the right phrenic nerve was documented before obtaining tissue samples for histological examination. Samples were collected at the root of the neck, near the inferior vena caval diaphragmatic hiatus, where the phrenic nerve splits into two main trunks. Thoracic posterior trunk (TPT) enters the abdominal cavity, and thoracic anterolateral trunk (TALT) supplies the right thoracic hemidiaphragm. Samples were also collected from identified abdominal branches. All sections were prepared using H&E and Luxol Fast Blue staining. Antibody staining for tyrosine hydroxylase was used to determine the presence of catecholaminergic fibers. The results were processed with ImageJ software for quantitative analysis. Results Lack of communication was observed between the cervical phrenic nerve and sympathetic cervical ganglia. No TH activity was detected, indicating an absence of catecholaminergic fibers in this area. The TALT showed an absence of TH activity throughout the effective surface area. Whereas TPT displayed 15% and the abdominal phrenic nerve 27% of catecholaminergic fibers. A branch to IVC of the Celio–Phrenic communication was identified in three specimens with an effective surface area of 0.049mm2, and 46-71% of this area contained TH-positive fibers. Conclusions Immunohistochemical analysis revealed an absence of catecholaminergic activity in the cervical area. This finding contradicts previous knowledge regarding cervical phrenic nerve anatomy and requires further investigation. TH positive fibers were only observed in the posterior trunk and absent in the TALT. Also, the prevalence of sympathetic fibers in the abdominal course of the phrenic nerve was evident. Thus, the lack of apparent communication between TALT and abdominal sympathetic ganglia resulted in the absence of sympathetic activity in the branch. These findings further support previous studies regarding the celiac plexus being a primary contributor of catecholaminergic fibers to the right phrenic nerve. Significance Understanding of the function requires profound expertise of the structure. Knowledge of sympathetic component within the phrenic nerve would clarify the autonomic role of the nerve, emphasizing the impact of proper respiration on overall health.

The Potential Repurposing Effect 4‐Aminopyridine in Nerve and Muscle Injury‐induced Bone Loss

Muscle injuries are one of the most common injuries occurring in physical and sporting activities, and account for 10-55% of all injuries. Peripheral nerve injury (PNI) itself accounts for 3-5% of all injuries in trauma patients, and muscle injuries can be concurrent with PNI because of their close proximity. Importantly, the peripheral nervous system is critically involved in bone metabolism, bone mineralization, and bone remodeling, and PNI results in substantial bone loss. While first aid for muscle injuries follows the conservative RICE (Rest, Ice, Compression and Elevation) principle, there is no medical treatment available after the acute phase except anti-inflammatory medications and rehabilitation. The poor healing process in damaged muscle, prolonged muscle disuse, and the lack of therapeutic strategies affect the performance of daily activities and predispose to further risk of muscle injury and bone loss. Therefore, there is an unmet need to develop therapeutic strategies that can help the recovery of damaged muscle and nerve, and limit bone loss. Recently we demonstrated the potential repurposing effect of 4-aminopyridine (4-AP), a potassium channel blocker, on neurogenic muscle atrophy and functional recovery after PNI in mice. However, it is unknown whether these beneficial effects of 4-AP are present in traumatic muscle injury and muscle injury-induced bone loss. This study was thus designed to evaluate the potential therapeutic effect of 4-AP in traumatic muscle healing and PNI-induced bone loss. Standardized crush injury was performed on right sciatic nerve, biceps femoris (BF) muscle (innervated by sciatic nerve), and quadriceps femoris (QF) muscle (innervated by femoral nerve) of adult male mice (6 animals/group). Post-surgical animals were randomly assigned to normal saline and 4-AP. 4-AP (40 µg, intraperitoneal) was given daily for 21 days, and the functional recovery after injury was assessed by sciatic function index (SFI), sensation by von Frey test (VFT), and grip strength test. After 21 days, the muscles at the injury/peri-injury site were processed for histomorphometry and tibial bone density was analyzed using DEXA scanning. We found that 4-AP significantly enhanced SFI, VFT, and hind limb paw grip strength from post-injury day 7, improved BF muscle morphology, cross-sectional area, and minimum ferret diameter, and totally reversed trauma-induced muscle fiber type composition changes (type-1 vs. type-2). 4-AP-induced muscle effects were also associated with a significantly increased number of regenerating stem cells (Pax7+) and proliferating cells (Ki67+) compared with saline group. Of note, 4-AP-induced muscle effects were either less pronounced or nonsignificant in QF muscle. Most importantly, 4-AP treatment significantly reduced PNI-induced bone loss by enhancing bone mineral density and bone mineral content. In conclusion, these interesting findings, for the first time, demonstrate the potential therapeutic effect of 4-AP on the recovery of traumatic muscle and bone loss after mixed muscle and nerve injury.

Management of The Posterior Cerebral Fossa Ependymomas

Background Posterior fossa brain ependymomas are one of the most devastating forms of human illnesses which are more common in children. Brainstem compression, herniation and death are the risks with tumours in this critical location. Patients and Methods: A retrospective study including 50 patients with posterior fossa ependymoma were performed at the Neurosurgery Department in Ait IDDIR University Hospital between the period of January 2005 and December 2015 . In each case, diagnosis was made clinically and confirmed radiologically and histo-pathologically.. All patients received the adjuvant treatment Results Out of 50 patients, 30 (60%) patients were males and 20 (40%) were females. The mean age was 24 years (ranged 5 months –47 years) ; we identified 29 (58%) children and 21 (42%) adults,. Ventriculo-peritoneal shunts were placed in all our patients, the total tumor excision was done to 35% and the partial tumor excision was done to 65% patients. The most common complications were as follows: Shunt malfunction : 4% , operative cavity hematoma 6%, CSF fistula 4%, deterioration of Cerebellar syndrome 6%, Cerebellar Mutism 2%, Mixed nerves palsy 4% and early post operative deaths 10%. Tumor architecture was classified as classic (Grade II) in 35 (70%) cases and anaplastic (Grade III) in 13(26%) cases. Adjuvant treatment regimens following resection included radiation therapy only (72%) for 36 patients including children above and adults and chemotherapy only (36%) for 9 children below 4 years and 9 recurrent tumors. During follow-up period, recurrence occurred in 27% 11patients out of 41patients .Five patients died (10%). Conclusion The surgical treatment of posterior fossa tumours still represents a challenge for neurosurgeons, Radical surgery with preservation of vital structures is the treatment of choice in patients with Posterior Cerebral Fossa ependymomas.. Our experience shows the accepted results, complications and surgical outcome in relation to previous clinical studies.

Two-Year Responses of Heart Rate and Heart Rate Variability to First Occupational Lead Exposure.

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Therapeutic Potential of Vagus Nerve Stimulation for Inflammatory Bowel Diseases.

The vagus nerve is a mixed nerve, comprising 80% afferent fibers and 20% efferent fibers. It allows a bidirectional communication between the central nervous system and the digestive tract. It has a dual anti-inflammatory properties via activation of the hypothalamic pituitary adrenal axis, by its afferents, but also through a vago-vagal inflammatory reflex involving an afferent (vagal) and an efferent (vagal) arm, called the cholinergic anti-inflammatory pathway. Indeed, the release of acetylcholine at the end of its efferent fibers is able to inhibit the release of tumor necrosis factor (TNF) alpha by macrophages via an interneuron of the enteric nervous system synapsing between the efferent vagal endings and the macrophages and releasing acetylcholine. The vagus nerve also synapses with the splenic sympathetic nerve to inhibit the release of TNF-alpha by splenic macrophages. It can also activate the spinal sympathetic system after central integration of its afferents. This anti-TNF-alpha effect of the vagus nerve can be used in the treatment of chronic inflammatory bowel diseases, represented by Crohn’s disease and ulcerative colitis where this cytokine plays a key role. Bioelectronic medicine, via vagus nerve stimulation, may have an interest in this non-drug therapeutic approach as an alternative to conventional anti-TNF-alpha drugs, which are not devoid of side effects feared by patients.

Peripheral Silent Period In Cervical and Generalized Dystonia

Objective: Dystonia is a movement disorder described by continuous or alternating muscle contractions causing unusual postures or insistent motions. Abnormal sensorimotor integration and abnormalities in inhibitory pathways are thought to have a role in pathogenesis. This paper aims to research the state of inhibitory pathways in the spinal cord in dystonia through documenting a silent period (SP) through cutaneous stimulation (CuSP) or mixed nerve stimulation (MnSP).
 Methods: 23 patients with dystonia were included in the study. Also, 19 healthy subjects were included in the study as a control group. Ages were similar between two groups. (p=0.092). CuSP and MnSP are recorded through abductor pollicis brevis and median nerve at the wrist respectively. 
 Results: Onset latency, time, and suppression index of CuSP were equivalent between two groups. Moreover, the initiation and terminate latencies of MnSP, also duration, were similar between these two groups. I2 suppression index was lower in generalized dystonia patients compared to patients with cervical dystonia (100.0 vs 86.7±21.4%; F=4.252, 0.035). 
 Conclusions: The most striking result to emerge from the data is that there was lower suppression during CuSP in generalized dystonia patients. Our results suggest that spinal inhibitory circuits are less active if only there is clinical involvement of the relevant segment.

Neuronal Actions of Transspinal Stimulation on Locomotor Networks and Reflex Excitability During Walking in Humans With and Without Spinal Cord Injury.

This study investigated the neuromodulatory effects of transspinal stimulation on soleus H-reflex excitability and electromyographic (EMG) activity during stepping in humans with and without spinal cord injury (SCI). Thirteen able-bodied adults and 5 individuals with SCI participated in the study. EMG activity from both legs was determined for steps without, during, and after a single-pulse or pulse train transspinal stimulation delivered during stepping randomly at different phases of the step cycle. The soleus H-reflex was recorded in both subject groups under control conditions and following single-pulse transspinal stimulation at an individualized exactly similar positive and negative conditioning-test interval. The EMG activity was decreased in both subject groups at the steps during transspinal stimulation, while intralimb and interlimb coordination were altered only in SCI subjects. At the steps immediately after transspinal stimulation, the physiological phase-dependent EMG modulation pattern remained unaffected in able-bodied subjects. The conditioned soleus H-reflex was depressed throughout the step cycle in both subject groups. Transspinal stimulation modulated depolarization of motoneurons over multiple segments, limb coordination, and soleus H-reflex excitability during assisted stepping. The soleus H-reflex depression may be the result of complex spinal inhibitory interneuronal circuits activated by transspinal stimulation and collision between orthodromic and antidromic volleys in the peripheral mixed nerve. The soleus H-reflex depression by transspinal stimulation suggests a potential application for normalization of spinal reflex excitability after SCI.

Analysis of the effect of intraoperative neuromonitoring during resection of benign nerve sheath tumors on gross-total resection and neurological complications.

The aim of this study was to examine the role of intraoperative neuromonitoring (IONM) during resection of benign peripheral nerve sheath tumors in achieving gross-total resection (GTR) and in reducing postoperative neurological complications. Data from consecutive adult patients who underwent resection of a benign peripheral nerve sheath tumor at 7 participating institutions were combined. Propensity score matching was used to balance covariates. The primary outcomes of interest were the association between IONM and GTR and the association of IONM and the development of a permanent postoperative neurological complication. The secondary outcomes of interest were the association between IONM and GTR and the association between IONM and the development of a permanent postoperative neurological complication in the subgroup of patients with tumors involving a motor or mixed nerve. Univariate and multivariate logistic regression were then performed on the propensity score-matched samples to assess the ability of the independent variables to predict the outcomes of interest. A total of 337 patients who underwent resection of benign nerve sheath tumors were included. In multivariate analysis, the use of IONM (OR 0.460, 95% CI 0.199-0.978; p = 0.047) was a significant negative predictor of GTR, whereas none of the variables, including IONM, were associated with the occurrence of a permanent postoperative neurological complication. Within the subgroup of motor/mixed nerve tumors, in the multivariate analysis, IONM (OR 0.263, 95% CI 0.096-0.723; p = 0.010) was a significant negative predictor of a GTR, whereas IONM (OR 3.800, 95% CI 1.925-7.502; p < 0.001) was a significant positive predictor of a permanent postoperative motor deficit. Overall, 12% of the cohort had a permanent neurological complication, with new or worsened paresthesias most common, followed by pain and then weakness. The authors found that formal IONM was associated with a reduced likelihood of GTR and had no association with neurological complications. The authors believe that these data argue against IONM being considered standard of care but do not believe that these data should be used to universally argue against IONM during resection of benign nerve sheath tumors.

Excitatory and inhibitory responses to cervical root magnetic stimulation in healthy subjects

ObjectivesTo characterize direct and reflex hand muscle responses to cervical root magnetic stimulation (CRMS) in healthy volunteers during sustained voluntary contraction. MethodsIn 18 healthy volunteers, we recorded from the first dorsal interosseous (FDI) muscle the responses to CRMS of progressively increasing intensity and level of muscle contraction. The compound muscle action potential (CMAP) and the silent period (SP) were compared to those obtained with plexus, midarm and wrist stimulation. Additionally, in a smaller number of subjects, we obtained the peristimulus time histogram (psth) of single motor unit firing in the FDI, examined the effects of vibration and recorded the modulation of sustained EMG activity in muscles of the lower limbs. ResultsIncreasing CRMS intensity led to larger CMAP with no relevant changes in SP1 or SP2, except for lower amplitude of the burst interrupting the silent period (BISP). Increasing the level of muscle contraction led to reduced CMAP, shorter SP duration and increased BISP amplitude. The psth analysis showed the underlying changes in the motor unit firing frequency that corresponded to the changes seen in the CMAP and the SP with surface recordings. Progressively distal stimulation led to CMAPs of shorter latency and increased amplitude, SPs of longer latency and shorter duration, and a BISP of longer latency. Vibration led to reduction of the SP. CRMS induced SPs in muscles of the lower limb. ConclusionsCRMS induces excitatory and inhibitory responses in hand muscles, fitting with the expected behavior of mixed nerve stimulation at very proximal sites. SignificanceCharacterization of the effects of CRMS on hand muscles is of physiological and potentially clinical applicability, as it is a painless and reliable procedure.

Methylene blue enhances polyethylene glycol-fusion repair of completely severed rat sciatic nerves.

Complete transection of peripheral mixed nerves immediately produces loss of sensory perception, muscle contractions and voluntary behavior mediated by the severed distal axons. In contrast to natural regeneration (~1 mm/d) of proximal axons that may eventually reinnervate denervated targets, re-innervation is restored within minutes by PEG-fusion that consists of neurorrhaphy and a sequence of well specified hypo- and isotonic calcium-free or calcium-containing solutions, the anti-oxidant methylene blue (MB) and the membrane fusogen polyethylene glycol (PEG). In this study, we examined the relative efficacy of PEG-fusion with no MB (0%), 0.5% MB, or 1% MB on the recovery of voluntary behaviors by female Sprague-Dawley rats with a complete mid-thigh severance of their sciatic nerve bathed in extracellular fluid or calcium-containing isotonic saline. The recovery of voluntary behaviors is the most relevant measure of success of any technique to repair peripheral nerve injuries. We assessed recovery by the sciatic functional index, a commonly used measure of voluntary hindlimb behaviors following complete sciatic transections. We reported that both 1% MB and 0.5% MB in sterile distilled water in our PEG-fusion protocol with neurorrhaphy significantly increased the rate and extent of behavioral recovery compared to PEG plus neurorrhaphy alone. Furthermore, 0.5% MB was as effective as 1% MB in voluntary behavioral recovery as assessed by the sciatic functional index. Since sterile 1% MB is no longer clinically available, we therefore recommend that 0.5% MB be included in upcoming human clinical trials to evaluate the safety and efficacy of PEG-fusion. All animal procedures were approved by the University of Texas Institutional Animal Care and Use Committee (AUP-2019-00225) on September 9, 2020.

Ulnar and Median Nerve Abnormalities in Carpal Tunnel Syndrome.

Nerve compression underlying carpal tunnel syndrome (CTS) results in an increase in the threshold of superficial sensation in the area supplied by the median nerve, which is a mixed nerve dominated by sensory fibres. The distribution of sensory symptoms is strongly dependent on the degree of electrophysiological dysfunction of the median nerve. The association between carpal tunnel syndrome and ulnar nerve entrapment at wrist level is still unclear. Patho-logical processes leading to median neuropathy in CTS may affect ulnar nerve motor and sensory fibers in the Guyon canal. This may explain the extra-median spread of sensory symptoms in CTS patients. The study involved 88 patients (104 hands), with 70 women (83 hands) and 18 men (21 hands) aged between 25 and 77 years. 50 age- and sex-matched subjects without carpal tunnel syndrome were used as a control group. The diagnosis of carpal tunnel syndrome was made according to the criteria of the American Academy of Neurology 1993 guidelines. Based on the results of an ENG trace evaluating the degree of conduction disturbances in the median nerve, the patients were classified to one of three severity subgroups. The threshold of sensory excitability to pulsed current was determined in a test with single 100 ms rectangular pulses. 1. The threshold of sensation in the fingers innervated by the median and ulnar nerve is significantly lon-ger in patients with CTS than in controls. 2. Surgical treatment decreases the threshold of sensation in the fingers innervated by the median nerve. 3. Surgical treatment does not decrease the threshold of sensation in the fingers innervated by the ul-nar nerve. 4. The preoperative and postoperative threshold of sensation in the fingers innervated by the median and ulnar nerve is significantly longer in patients with severe carpal tunnel than in mild and moderate cases.

Structural Origin and Surgical Complications of Peripheral Schwannomas.

In this study, we investigated the locations and surgical complications of schwannomas. Data of 130 patients with schwannomas were retrospectively reviewed. Pre- and post-operative neurological symptoms, tumor locations, and nerves of origin (sensory, motor, or mixed) were reviewed. Before surgery, 69 patients had Tinel-like signs, 56 patients had pain, 32 patients had numbness, four patients had motor deficits. After surgery, 20 patients had developed a new neurological deficit; 11 patients had motor deficits, ten patients had sensory deficits, and one patient had both motor and sensory deficits. Most schwannomas occurred in mixed nerves, including the median nerve in 17 patients and tibial nerve in 13 patients. The most common site of schwannoma was the median nerve. Although the nerve of origin of the schwannoma could be identified in only 26.0% of cases, the data suggest that schwannomas occur in both sensory and motor nerves.

The science behind programming algorithms for sacral neuromodulation.

Sacral neuromodulation (SNM) is a widely adopted treatment for overactive bladder, non-obstructive urinary retention and faecal incontinence. In the majority, it provides sustained clinical benefit. However, it is recognized that, even for these patients, stimulation parameters (such as amplitude, electrode configuration, frequency and pulse width) may vary at both initial device programming and at reprogramming, the latter often being required to optimize effectiveness. Although some recommendations exist for SNM programming, the scientific data to support them are understood by few clinicians. This is a narrative review of the literature covering some of the science behind stimulating a mixed peripheral nerve and available preclinical data in the field of SNM. It covers electrode configuration, amplitude, frequency, pulse width and cycling considerations. The review is targeted at clinicians with an interest in the field and does not seek to provide exhaustive detail on basic neuroscience. Knowledge of the science of neuromodulation provides some guiding principles for programming but these are broad. These principles are not refuted by preclinical data but specific parameters in clinical use are not strongly supported by animal data, even after the limitations of small and large animal models are considered. The review presents a shortlist of programming principles on a theoretical basis but acknowledges that current practice is as much derived from evolved experience as science.

Comparison of Borderline Ultrasound and Nerve Conduction Studies for Carpal Tunnel Syndrome.

Choosing cutoff values for nerve conduction studies (NCS) and ultrasound cross-sectional area (CSA) in the diagnosis of carpal tunnel syndrome (CTS) is critical in determining the diagnostic accuracy of the tests. The goals of this study were to: (1) determine the sensitivity and specificity of various electrodiagnostic and ultrasound threshold values for diagnosis of CTS; and (2) determine the number of hands that underwent NCS and ultrasound that were within 10% of threshold values. A total of 309 hands of 235 patients were included in this study. Diagnosis of median neuropathy was made based on NCS by the independent physician performing the NCS. Criteria analyzed included distal motor latency of 4.4+ ms, distal sensory latency of 3.6+ ms, difference in median-ulnar mixed nerve palmar latency of 0.4+ ms, and CSA of the median nerve of 10+ mm2. Median neuropathy was diagnosed in 235 hands, whereas 74 hands were found not to have median neuropathy. Overall, 141 hands (46%) had at least 1 of the 3 electrodiagnostic variables within 10% of the diagnostic cutoff values, and 137 hands (44%) had a median nerve CSA within 10% of 10 mm2. By performing ultrasound in addition to NCS for each patient, an additional 65 hands (21%) had a definitive diagnosis on at least 1 of the 2 diagnostic modalities. Ultrasound and NCS yielded a similar number of patients within 10% of their diagnostic threshold values. When used together, the number of patients with a nonborderline diagnosis on at least 1 diagnostic modality was increased substantially.

In Response.

Thank you Dr Raghuraman1 for the thoughtful insights and comments on both the study by Barrington et al,2 as well as our editorial.3 The main purpose of the editorial was to promote awareness of the complex anatomy of the chest wall and breast to assure that the choice of block is appropriate for the various types of surgery. It is clear that you apply an intricate understanding of this anatomy, but we would like to clarify 2 items. While we very much agree that the medial and lateral pectoral nerves are mixed sensory and motor nerves that innervate the pectoralis major and minor muscles and their associated fascia, there is no evidence that they provide any sensory innervation to the skin, subcutaneous tissue, or breast parenchyma.4 Thus, there is no anatomic basis to support the theory that blockade of these nerves would provide analgesia for wide local excision (WLE) surgery. For surgeries such as WLE that only violate the skin and subcutaneous tissue (including breast parenchyma), the benefit of PECS II block stems from blockade of the lateral cutaneous branches of the intercostal nerves.4 You also mention the recent trial by Altiparmak et al.5 We would hesitate to place much emphasis on the findings of this study given 2 significant methodological issues with its protocol. First, the reported sample size was changed from 30 to 38 after patient recruitment was completed. Second, the reported primary outcome was changed from pain to tramadol consumption after the end of patient enrollment. In general, any future evidence to support a benefit for PECS II block over erector spinae plane block (ESPB) in surgeries that violate the chest wall muscles or facia, for example, modified radical mastectomy (MRM), would not be surprising. PECS II block targets the brachial plexus nerves supplying these muscles and fascia in addition to the lateral cutaneous branches of the intercostal nerves, while ESPB presumably blocks the intercostal nerves and their branches but spares the brachial plexus nerves. Pain from MRM surgery is multifactorial, but disruption of the deep chest wall fascia that is innervated by the brachial plexus likely plays a very significant role in postoperative pain. Robert B. Maniker, MD, MSDepartment of Anesthesiology and Perioperative MedicineColumbia University College of Physicians and SurgeonsNew York, New York[email protected]Rebecca L. Johnson, MDDepartment of AnesthesiologyMayo Clinic College of MedicineRochester, MinnesotaDe Q. Tran, MD, FRCPCDepartment of AnesthesiaMcGill UniversityMontreal, Quebec, Canada

SENSITIVITIES OF THE ELECTRODIAGNOSTIC TESTS IN IDIOPATHIC MILD CARPAL TUNNEL SYNDROME

OBJECTIVE: Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy. The diagnosis is based on the history, clinical signs and symptoms of the patient, but electrodiagnostic studies are done to confirm the diagnosis and to manage the treatment. This study aimed to assess sensitivities of clinical symptoms, provocative tests and electrodiagnostic studies (EDS) in patients with idiopathic mild CTS.MATERIAL AND METHODS:The study included 90 hands of 75 patients with idiopathic mild CTS and 30 hands of 15 healthy volunteers. The patients were questioned for symptoms in the innervation area of the median nerve such as pain, paresthesia, weakness in the hand and numbness and pain worsening at night, relief from the symptoms by shaking hands. Tinel and Phalen tests were done. The EDS included; motor, mixed and sensorial (digits 1-2-3-4 and palm) nerve conduction studies (NCS) for median nerve; motor, mixed and sensorial (fifth digit) NCS for ulnar nerve, sensorial NCS (first digit) for radial nerve, median and ulnar F waves. The values for distal latency and nerve conduction velocity (NCV) were calculated for all studied nerves. Sensitivities of median sensory distal latency and NCV to digits 1,2,3,4 and palm-wrist segments and sensitivities of the following comparative tests were detected; median-radial sensory distal latency difference (SDLD) to the first digit, median-ulnar SDLD to the fourth digit, median-ulnar SDLD to the digits 2-5, 3-5, 4-5 and median-ulnar F latency difference.RESULTS: The most common symptoms in patients with idiopathic mild CTS were paresthesia (95.6%) and nocturnal numbness (88.8%). The sensitivity of Phalen’s and Tinel’s tests were 67.8% and 56.7%, respectively. Among the EDS, first digit and palm-wrist sensorial NCV were the most sensitive tests (98.9%). Of the comparative tests, median-ulnar SDLD to digits 4-5 was the most sensitive one (93.3%). Median-ulnar F latency difference had the lowest sensitivity (38.9%).CONCLUSIONS: The most sensitive EDS were first digit and palm-wrist sensorial NCV. Median-ulnar SDLD to digits 4-5 was more sensitive than the other tests. With use of these tests, the diagnostic sensitivity of EDS may be increased in patients with mild CTS.