Axillary and musculocutaneous neuropathies.

This chapter covers axillary and musculocutaneous neuropathies, with a focus on clinically relevant anatomy, electrodiagnostic approaches, etiologic considerations, and management principles. Disorders of the lateral antebrachial cutaneous nerve, a derivative of the musculocutaneous nerve, are also reviewed. We emphasize the importance of objective findings, including the physical examination and electrodiagnostic evaluation in confirming the isolated involvement of each nerve which, along with the clinical history, informs etiologic considerations. Axillary and musculocutaneous neuropathies are both rare in isolation and most frequently occur in the setting of trauma. Less commonly encountered etiologies include external compression or entrapment, neoplastic involvement, or immune-mediated disorders including neuralgic amyotrophy, postsurgical inflammatory neuropathy, multifocal motor neuropathy, vasculitic neuropathy, and multifocal chronic inflammatory demyelinating polyradiculoneuropathy.

Ulnar neuropathy.

Ulnar neuropathy at the elbow is the second most common compressive neuropathy. Less common, although similarly disabling, are ulnar neuropathies above the elbow, at the forearm, and the wrist, which can present with different combinations of intrinsic hand muscle weakness and sensory loss. Electrodiagnostic studies are moderately sensitive in diagnosing ulnar neuropathy, although their ability to localize the site of nerve injury is often limited. Nerve imaging with ultrasound can provide greater localization of ulnar injury and identification of specific anatomical pathology causing nerve entrapment. Specifically, imaging can now reliably distinguish ulnar nerve entrapment under the humero-ulnar arcade (cubital tunnel) from nerve injury at the retro-epicondylar groove. Both these pathologies have historically been diagnosed as either "ulnar neuropathy at the elbow," which is non-specific, or "cubital tunnel syndrome," which is often erroneous. Natural history studies are few and limited, although many cases of mild-moderate ulnar neuropathy at the elbow appear to remit spontaneously. Conservative management, perineural steroid injections, and surgical release have all been studied in treating ulnar neuropathy at the elbow. Despite this, questions remain about the most appropriate management for many patients, which is reflected in the absence of management guidelines.

Sciatic and tibial neuropathies.

The sciatic nerve is the body's largest peripheral nerve. Along with their two terminal divisions (tibial and fibular), their anatomic location makes them particularly vulnerable to trauma and iatrogenic injuries. A thorough understanding of the functional anatomy is required to adequately localize lesions in this lengthy neural pathway. Proximal disorders of the nerve can be challenging to precisely localize among a range of possibilities including lumbosacral pathology, radiculopathy, or piriformis syndrome. A correct diagnosis is based upon a thorough history and physical examination, which will then appropriately direct adjunctive investigations such as imaging and electrodiagnostic testing. Disorders of the sciatic nerve and its terminal branches are disabling for patients, and expert assessment by rehabilitation professionals is important in limiting their impact. Applying techniques established in the upper extremity, surgical reconstruction of lower extremity nerve dysfunction is rapidly improving and evolving. These new techniques, such as nerve transfers, require electrodiagnostic assessment of both the injured nerve(s) as well as healthy, potential donor nerves as part of a complete neurophysiological examination.

The role of electrodiagnosis in focal neuropathies.

Electrodiagnostic (EDX) testing plays an important role in confirming a mononeuropathy, localizing the site of nerve injury, defining the pathophysiology, and assessing the severity and prognosis. The combination of nerve conduction studies (NCS) and needle electromyography findings provides the necessary information to fully assess a nerve. The pattern of NCS abnormalities reflects the underlying pathophysiology, with focal slowing or conduction block in neuropraxic injuries and reduced amplitudes in axonotmetic injuries. Needle electromyography findings, including spontaneous activity and voluntary motor unit potential changes, complement the NCS findings and further characterize chronicity and degree of axon loss and reinnervation. EDX is used as an objective marker to follow the progression of a mononeuropathy over time.

The role of imaging in focal neuropathies.

Electrodiagnostic testing (EDX) has been the diagnostic tool of choice in peripheral nerve disease for many years, but in recent years, peripheral nerve imaging has been used ever more frequently in daily clinical practice. Nerve ultrasound and magnetic resonance (MR) neurography are able to visualize nerve structures reliably. These techniques can aid in localizing nerve pathology and can reveal significant anatomical abnormalities underlying nerve pathology that may have been otherwise undetected by EDX. As such, nerve ultrasound and MR neurography can significantly improve diagnostic accuracy and can have a significant effect on treatment strategy. In this chapter, the basic principles and recent developments of these techniques will be discussed, as well as their potential application in several types of peripheral nerve disease, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), radial neuropathy, brachial and lumbosacral plexopathy, neuralgic amyotrophy (NA), fibular, tibial, sciatic, femoral neuropathy, meralgia paresthetica, peripheral nerve trauma, tumors, and inflammatory neuropathies.

Other median neuropathies.

Median mononeuropathy is common, with carpal tunnel syndrome the most frequently encountered acquired mononeuropathy in clinical practice. However, other disorders of the median nerve and many known anatomical variants can lead to misdiagnosis and unexpected surgical complications if their presence is not correctly identified. A number of inherited and acquired disorders can affect the median nerve proximal to the wrist, alone or accompanied by other affected peripheral nerves. Recognizing other disorders that can masquerade as median mononeuropathies can avoid misdiagnosis and misguided management. This chapter explores median nerve anatomical variants, disorders, and lesions, emphasizing the need for careful examination and electrodiagnostic study in the localization of median neuropathy.

Peripheral Neuropathy.

Peripheral neuropathy is a commonly encountered diagnosis in both neurology and primary care office settings. It is important for primary care providers to identify, characterize, and diagnose patients with neuropathy. This study aims to describe the clinical presentation, diagnostic work up, and treatment options for this entity, as well as the identification of atypical features that should prompt specialized laboratory testing, electrodiagnostic testing, and neurologic consultation.

Traumatic and iatrogenic sciatic nerve injury in 38 dogs and 10 cats: Clinical and electrodiagnostic findings.

BACKGROUND: Reports describing sciatic nerve injuries (SNI) and their outcome are scarce in veterinary medicine. HYPOTHESIS: Describe the causes of traumatic and iatrogenic SNI and evaluate which clinical and electrodiagnostic findings predict outcome. ANIMALS: Thirty-eight dogs and 10 cats with confirmed SNI referred for neurologic and electrodiagnostic evaluation. METHODS: Clinical and electrodiagnostic examination results, including electromyography (EMG), motor nerve conduction studies, muscle-evoked potential (MEP), F-waves, sensory nerve conduction studies, and cord dorsum potential (CDP), were retrospectively evaluated. Quality of life (QoL) was assessed based on owner interviews. RESULTS: Surgery (42%) and trauma (33%) were the most common causes of SNI; in dogs, 24% were caused by bites from wild boars. Ability to flex and extend the tarsus was significantly associated with positive outcome in dogs. Mean time from onset of clinical signs until electrodiagnostic evaluation was 67 ± 65 (range, 7-300) days and 65 ± 108 (range, 7-365) days for dogs and cats, respectively. A cut-off amplitude of 1.45 mV for compound motor action potentials (CMAP) was predictive of positive outcome in dogs (P = .01), with sensitivity of 58% and specificity of 100%. CONCLUSIONS AND CLINICAL IMPORTANCE: Clinical motor function predicts recovery better than sensory function. Electrodiagnostic findings also may play a role in predicting the outcome of SNI. Application of the proposed CMAP cut-off amplitude may assist clinicians in shortening the time to reassessment or for earlier suggestion of salvage procedures. Owners perceived a good quality of life (QoL), even in cases of hindlimb amputation.

Volumetric assessment of ulnar nerves in cubital tunnel syndrome with 3D modeling of the MRI and its relationship with electrodiagnostic findings.

BACKGROUND: Thickened nerve cross-sectional areas (CSA) have been investigated in compressive neuropathy, but the longitudinal extent of nerve swelling has yet to be evaluated. We did a volumetric assessment of the ulnar nerve in cubital tunnel syndrome (CuTS) with three-dimensional (3D) magnetic resonance imaging (MRI) modeling and investigated this relationship with clinical and electrodiagnostic parameters. METHODS: We compared 40 CuTS patient elbow MRIs to 46 patient elbow MRIs with lateral elbow epicondylitis as controls. The ulnar nerve was modeled with Mimics software and was assessed qualitatively and quantitatively. The CSA and ulnar nerve volumes were recorded, and the area under the receiver operating characteristic (ROC) curve was calculated for diagnostic performance. We analyzed clinical and electrodiagnostic parameters to investigate their relationship with the 3D ulnar nerve parameters. RESULTS: For the diagnosis of CuTS, the area under the curve value was 0.915 for the largest CSA and 0.910 for the volume in the ROC curve. The optimal cut-off was 14.53 mm2 and 529 mm3 respectively. When electrodiagnostic parameters were investigated, the 3D ulnar nerve volume was significantly inversely associated with motor conduction velocity, although there was no association between the largest CSA and any of the electrodiagnostic parameters. CONCLUSIONS: The 3D ulnar nerve volume, which is an integration or multilevel measurement of CSAs, showed diagnostic usefulness similar to CSA, but it correlated better with conduction velocity, indicating demyelination or early-to-moderate nerve damage in CuTS.

A robust multi-branch multi-attention-mechanism EEGNet for motor imagery BCI decoding.

BACKGROUND: Motor-Imagery-based Brain-Computer Interface (MI-BCI) is a promising technology to assist communication, movement, and neurological rehabilitation for motor-impaired individuals. Electroencephalography (EEG) decoding techniques using deep learning (DL) possess noteworthy advantages due to automatic feature extraction and end-to-end learning. However, the DL-based EEG decoding models tend to show large variations due to intersubject variability of EEG, which results from inconsistencies of different subjects' optimal hyperparameters. NEW METHODS: This study proposes a multi-branch multi-attention mechanism EEGNet model (MBMANet) for robust decoding. It applies the multi-branch EEGNet structure to achieve various feature extractions. Further, the different attention mechanisms introduced in each branch attain diverse adaptive weight adjustments. This combination of multi-branch and multi-attention mechanisms allows for multi-level feature fusion to provide robust decoding for different subjects. RESULTS: The MBMANet model has a four-classification accuracy of 83.18% and kappa of 0.776 on the BCI Competition IV-2a dataset, which outperforms other eight CNN-based decoding models. This consistently satisfactory performance across all nine subjects indicates that the proposed model is robust. CONCLUSIONS: The combine of multi-branch and multi-attention mechanisms empowers the DL-based models to adaptively learn different EEG features, which provides a feasible solution for dealing with data variability. It also gives the MBMANet model more accurate decoding of motion intentions and lower training costs, thus improving the MI-BCI's utility and robustness.

Serial electrodiagnostic testing: Utility and indications in adult neurological disorders.

Although existing guidelines address electrodiagnostic (EDX) testing in identifying neuromuscular conditions, guidance regarding the uses and limitations of serial (or repeat) EDX testing is limited. By assessing neurophysiological change longitudinally across time, serial electrodiagnosis can clarify a diagnosis and potentially provide valuable prognostic information. This monograph presents four broad indications for serial electrodiagnosis in adult peripheral neurological disorders. First, where clinical change has raised suspicion for a new or ongoing lesion, EDX reassessment for spatial spread of abnormality, involvement of previously normal muscle or nerve, and/or evolving pathophysiology can clarify a diagnosis. Second, where diagnosis of a progressive neuromuscular condition is uncertain, electrophysiological data from a second time point can confirm or refute suspicion. Third, to establish prognosis after a static nerve injury, a repeat study can assess the presence and extent of reinnervation. Finally, faced with a limited initial study (as when complicated by patient or environmental factors), a repeat EDX study can supplement missing or limited data to provide needed clarity. Repeat EDX studies carry certain limitations, however, such as with prognostication in the setting of remote or chronic lesions, sensory predominant fascicular injury, or mild axonal injury. Nevertheless, serial electrodiagnosis remains a valuable and underused tool in the diagnostic and prognostic evaluation of neuromuscular conditions.

Prognostic value of electroneurography using the midline method for predicting the development of synkinesis after peripheral facial palsy.

OBJECTIVE: The prognostic value of electroneurography (ENoG) for predicting the incidence of synkinesis is reportedly about 40 % using the formal standard method (ENoG-SM). However, the prognostic value of ENoG using the newly developed midline method (ENoG-MM) has not been determined. The aim of this study was to demonstrate the optimal prognostic value and advantages of ENoG-MM for predicting the incidence of synkinesis. METHODS: Participants were 573 patients treated for peripheral facial palsy including Bell's palsy or Ramsay Hunt syndrome. We investigated the clinical presence of any oral-ocular or ocular-oral synkinesis from the medical records. ENoG-MM and ENoG-SM were performed 10-14 days after symptom onset. In ENoG-MM, compound muscle action potentials were recorded by placing the anode on the mental protuberance and the cathode on the philtrum. In ENoG-SM, electrodes were placed on the nasolabial fold. Synkinesis was clinically assessed at the end of follow-up or at >1 year after onset. The sensitivity and specificity of ENoG values for predicting the incidence of synkinesis were compared between ENoG-MM and ENoG-SM at every 5 % around 40 % (range, 30-50 %). RESULTS: At every 5 % of ENoG values around 40 %, ENoG-MM provided higher sensitivity and lower specificity for predicting the incidence of synkinesis compared with ENoG-SM. In particular, when the cut-off value was set at 45 %, sensitivity was 100 % and 95.3 % with ENoG-MM and ENoG-SM, respectively. CONCLUSION: In peripheral facial palsy, ENoG-MM offered higher sensitivity than ENoG-SM for predicting synkinesis. ENoG-MM is useful for screening patients at risk of developing synkinesis. In clinical practice, an ENoG-MM cut-off value of 45 % must be the optimal prognostic value because of the 100 % sensitivity.

Electrodiagnostic studies and new diagnostic modalities for evaluation of peripheral nerve disorders.

Electrodiagnostic studies (EDx) are frequently performed in the diagnostic evaluation of peripheral nerve disorders. There is increasing interest in the use of newer, alternative diagnostic modalities, in particular imaging, either to complement or replace established EDx protocols. However, the evidence to support this approach has not been expansively reviewed. In this paper, diagnostic performance data from studies of EDx and other diagnostic modalities in common peripheral nerve disorders have been analyzed and described, with a focus on radiculopathy, plexopathy, compressive neuropathies, and the important neuropathy subtypes of Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), vasculitic neuropathy and diabetic neuropathy. Overall EDx retains its place as a primary diagnostic modality in the evaluated peripheral nerve disorders. Magnetic resonance imaging and ultrasound have developed important complementary diagnostic roles in compressive and traumatic neuropathies and atypical CIDP, but their value is more limited in other neuropathy subtypes. Identification of hourglass constriction in nerves of patients with neuralgic amyotrophy may have therapeutic implications. Investigation of radiculopathy is confounded by poor correlation between clinical features and imaging findings and the lack of a diagnostic gold standard. There is a need to enhance the literature on the utility of these newer diagnostic modalities.

Análisis de los parámetros ecográficos descritos en el estudio del síndrome del túnel del carpo. Una revisión sistemática / Analysis of the echographic parameters described in the study of carpal tunnel syndrome: A systematic review

El síndrome del túnel del carpo (STC) es la mononeuropatía por atrapamiento más frecuente; el diagnóstico se establece mediante pruebas electrodiagnósticas con un número sustancial de falsos positivos/negativos. Presentamos la siguiente revisión sistemática, cuyo objetivo es analizar la literatura más reciente en relación con los parámetros ecográficos descritos para estudiar el STC. Seleccionamos estudios que evaluasen parámetros ecográficos en pacientes con sospecha clínica, siguiendo las recomendaciones del manual Cochrane; incluimos revisiones sistemáticas, metaanálisis, estudios caso-control y de pruebas diagnósticas, valorando estudios retrospectivos y revisiones bibliográficas con buena calidad metodológica. La revisión se hizo de artículos publicados entre 2005-2019. Incluimos 8 artículos (2 revisiones sistemáticas/metaanálisis, 2 estudios caso-control, un estudio de pruebas diagnósticas, 2 revisiones literarias y un estudio retrospectivo). Los parámetros analizados fueron el área de sección transversa del nervio mediano, el índice muñeca-antebrazo, el índice entrada-salida, el rango de adelgazamiento del nervio mediano, el abombamiento del retináculo flexor y la vascularización/movilidad. La evidencia actual permite afirmar que la ecografía tiene utilidad en el cribado del STC.(AU)

Carpal tunnel syndrome (CTS) is the most common entrapment mononeuropathy; the diagnosis is established by electrodiagnostic tests with until 34% of false positives/negatives. We present the following systematic review which objective is to analyze the most recent literature related to the ultrasound parameters described to study CTS. We selected studies that evaluated ultrasound parameters in patients with clinical suspicion following the Cochrane manual's recommendations. We include systematic reviews, meta-analyses, case–control studies and diagnostic tests, evaluating retrospective studies and bibliographic reviews with proper methodological quality. Articles published between 2005 and 2019. We included eight articles (two systematic reviews/meta-analyses, two case–control studies, one diagnostic test study, two literature reviews, and one retrospective). The parameters analyzed were cross-sectional area, wrist–forearm index, entry–exit index, thinning range, palmar bowing of the flexor retinaculum, and vascularity/mobility. Current evidence allows us to affirm that ultrasound is useful in screening for CTS.(AU)

Electrodiagnostic methods to verify Guillain-Barré syndrome subtypes in Istanbul: A prospective multicenter study.

BACKGROUND AND AIMS: This study aimed to identify the clinical characteristics and electrodiagnostic subtypes of Guillain-Barré syndrome (GBS) in Istanbul. METHODS: Patients with GBS were prospectively recruited between April 2019 and March 2022 and two electrodiagnostic examinations were performed on each patient. The criteria of Ho et al., Hadden et al., Rajabally et al., and Uncini et al. were compared for the differentiation of demyelinating and axonal subtypes, and their relations with anti-ganglioside antibodies were analyzed. RESULTS: One hundred seventy-seven patients were included, 69 before the coronavirus disease 2019 pandemic (April 2019-February 2020) and 108 during the pandemic (March 2020-March 2022), without substantial changes in monthly frequencies. As compared with the criteria of Uncini et al., demyelinating GBS subtype diagnosis was more frequent according to the Ho et al. and Hadden et al. criteria (95/162, 58.6% vs. 110/174, 63.2% and 121/174, 69.5%, respectively), and less frequent according to Rajabally et al.'s criteria (76/174, 43.7%). Fourteen patients' diagnoses made using Rajabally et al.'s criteria were shifted to the other subtype with the second electrodiagnostic examination. Of the 106 analyzed patients, 22 had immunoglobulin G anti-ganglioside antibodies (14 with the axonal subtype). They had less frequent sensory symptoms (54.5% vs. 83.1%, p = 0.009), a more frequent history of previous gastroenteritis (54.5% vs. 22.9%, p = 0.007), and a more severe disease as compared with those without antibodies. INTERPRETATION: Serial electrodiagnostic examinations are more helpful for accurate subtype diagnosis of GBS because of the dynamic pathophysiology of the disease. We observed no significant increase in GBS frequency during the pandemic in this metropolis.

Subjective and Objective Differences in Patients with Unilateral and Bilateral Carpal Tunnel Syndrome and the Role of Obesity in Syndrome Severity.

BACKGROUND: It remains unclear whether physiologic differences exist in musculoskeletal ultrasound nerve measurements when comparing bilateral and unilateral carpal tunnel syndrome (CTS) patients. Similarly, the influence of body mass index on CTS severity is not well characterized. METHODS: Unilateral and bilateral CTS patients were seen from October of 2014 to February of 2021. Obese and nonobese CTS patients were compared. Median nerve cross-sectional area (CSA), Boston Carpal Tunnel Syndrome Questionnaire (BCTSQ), and six-item Carpal Tunnel Symptom Score (CTS-6) measures were obtained. Nerve conduction studies recorded distal motor latency (DML) and distal sensory latency (DSL). Statistical analysis used Wilcoxon signed rank testing for paired continuous variables, Mann-Whitney U testing for nonpaired continuous variables, and chi-square testing for continuous variables, with a significance level of P < 0.05. RESULTS: A total of 109 (218 nerves) bilateral and 112 (112 nerves) unilateral CTS patients were reviewed. Bilateral patients had larger median nerve CSAs on their more symptomatic side, when defined by BCTSQ score ( P < 0.0001), CTS-6 score ( P < 0.0001), DML ( P < 0.0001), and DSL ( P < 0.01). Bilateral patients also had higher symptom severity scale ( P < 0.01) and DSL ( P < 0.001) outcomes compared with unilateral patients. Obese patients had higher median nerve CSA ( P < 0.01), prolonged DML, and prolonged DSL ( P < 0.0001) values despite similar CTS severity (BCTSQ and CTS-6). CONCLUSIONS: Ultrasound identifies the more symptomatic side in bilateral patients, which correlates with increasing severity (NCS and BCTSQ). Obesity increases median nerve CSA and prolongs nerve conduction studies without influencing CTS severity. This information can be used when considering which diagnostic test to order for CTS.

A review of electromyography techniques of the cervical paraspinal muscles.

Electrodiagnosis for cervical radiculopathy often involves exploration of the cervical paraspinal muscles. Accurate and reproducible results require a technique with specific anatomic localization, direction of insertion, extent of insertion, scoring system for insertion, and criteria for determining abnormality. We sought to understand if a published technique met these criteria. A Medline search found 39 articles with original research and 10 review articles involving the cervical paraspinals. A library search found 19 textbooks since 2000, but 9 were not available. Only two studies were specific to the question. Neither had reproducible techniques and they contradicted each other. Studies in which the paraspinals were used for comparison or inclusion did not provide any specific technique. The review articles and textbooks typically met none of our criteria and the few that discussed technique at all provided no reproducible methods. Despite 80 years of electrodiagnostic testing, there is no useful, reproducible technique for exploring the cervical paraspinal muscles. Yet such a paraspinal mapping technique has proven invaluable in the lumbar region. For cervical electromyography to be of value, the next step is to understand the anatomy and propose a reproducible technique. Subsequent research will determine whether the neck muscles are helpful in the diagnosis of cervical radiculopathy. The absence of a valid reproducible cervical paraspinal technique impedes clinical and scientific understanding of cervical radiculopathy.

Electrodiagnostic findings in amyotrophic lateral sclerosis: Variation with region of onset and utility of thoracic paraspinal muscle examination.

INTRODUCTION/AIMS: Limited data exist regarding variation of electrodiagnostic (EDX) findings in amyotrophic lateral sclerosis (ALS) patients with different onset regions and specificity of thoracic paraspinal muscle (TPSP) examination for confirming a diagnosis of ALS. We aimed to demonstrate the variation of EDX features and characterize the utility of TPSP muscle examination in the electrodiagnosis of ALS. METHODS: This is a retrospective study of a large cohort of ALS patients who had a comprehensive EDX evaluation. RESULTS: The study included 448 patients; all fulfilled the Gold Coast criteria for ALS. The average age at the time of EDX study was 64 years, and 41.1% were women. The onset region was identified as follows: bulbar (N = 149), cervical (N = 127), lumbosacral (N = 162), and other (N = 10). In contrast to limb onset, bulbar-onset patients more frequently demonstrated a pattern of normal or near normal needle electromyography (EMG) (p < .0001) and less frequently had abnormalities on EMG of TPSP (p = .002). Clinical or EDX diagnosis of sensory polyneuropathy was present in 12.6% patients, more frequently in the lumbosacral onset subgroup (p < .03). EMG showed active denervation in 9.6% and chronic denervation in 59% of craniobulbar muscles examined, without observed difference among different onset regions. TPSP showed higher frequencies of active and chronic denervation in ALS than a group of patients with non-ALS neuromuscular disorders. DISCUSSION: EDX features may differ among ALS patients of different onset regions. TPSP EMG is highly useful in differentiating ALS from non-ALS neuromuscular disorders while the yield of craniobulbar muscles, especially for active denervation, is low.

Comparison of electrodiagnostic findings in acute traumatic versus chronic non-traumatic ulnar neuropathy at the elbow.

INTRODUCTION/AIMS: A common concept is that traumatic nerve injuries are more likely axonal, and that compressive neuropathies are more likely demyelinating. The purpose of this study was to compare traumatic versus non-traumatic ulnar neuropathy at the elbow (UNE) to look for electrodiagnostic differences between the two groups. METHODS: A retrospective 3 year review of UNE patients at two academic health science centers was conducted. Patients were grouped into acute traumatic UNE versus chronic non-traumatic UNE based on clinical history. Electrodiagnostic measurements were compared between the two groups. RESULTS: There were 50 subjects with acute traumatic UNE and 41 with chronic non-traumatic UNE. Mean age and sex distribution were similar but those with traumatic UNE had a 7 month duration of symptoms, while those with chronic UNE had 29 month duration (p < .001). All electrodiagnostic measurements were similar between the two groups including compound muscle action potential amplitudes, motor conduction velocities, frequency of conduction block, sensory nerve studies, and needle electromyography. DISCUSSION: We did not find a difference between the two groups. One should not make inferences regarding acuity or etiology based on electrodiagnostic features alone.