Prolonged Distal Latencies Research Articles

Proximal Median Nerve Conduction Velocity Slowing in Carpal Tunnel Syndrome: An Observational Retrospective Study.

Carpal Tunnel Syndrome (CTS) is the most common entrapment neuropathy, characterised by compression of the median nerve at the wrist. Traditional understanding views CTS as a distal compression issue, but recent evidence suggests potential proximal involvement. This study aimed to assess the prevalence of proximal median nerve conduction velocity (CV) slowing in CTS patients and examine its association with CTS severity. In this retrospective observational study, data were analysed from 80 CTS patients and 40 controls from the Electrophysiology Lab at a tertiary care institute. Nerve conduction studies (NCS) evaluated the median nerve's conduction velocity and latency. Patients were classified by CTS severity, and nerve conduction parameters were statistically compared between groups. CTS patients exhibited significantly prolonged distal motor latency (DML) (5.2 ± 0.8 ms) and reduced forearm motor conduction velocity (MCV) (55.3 ± 4.1 m/s) compared to controls (P < .01). Approximately 27.45% of CTS hands showed proximal median nerve slowing. The severity classification showed that Grade 3 CTS was the most prevalent (47%), followed by Grade 2 (23%) and Grade 1 (10%). There was a negative correlation between distal latency and forearm conduction velocity, suggesting that as distal latency increases, forearm conduction velocity decreases. Post-operatively, significant improvements were observed in distal latency (mean decrease: 1.2 ± 0.5 ms, P < .01), but median nerve conduction velocity remained unchanged. While there was a trend towards improvement in CMAP amplitude, the difference did not reach statistical significance. A subset of CTS cases exhibits reduced proximal median nerve conduction velocity, which correlates with CTS severity. This suggests retrograde degeneration may contribute to CTS pathology, challenging the traditional view of CTS as a purely distal compression disorder.

Clinical and Electrophysiological Characteristics of 23 French Patients With Neurolymphomatosis.

Neurolymphomatosis is a hematological condition defined by the direct infiltration of malignant lymphomatous cells into the peripheral nervous system. Since nerve conduction studies may disclose demyelinating features, clinicians may misdiagnose neurolymphomatosis as chronic inflammatory demyelinating polyneuropathy (CIDP). This study aimed to determine whether patients with neurolymphomatosis met the 2021 revised criteria for CIDP. We retrospectively analyzed 23 patients with primary or secondary neurolymphomatosis from nine French hospitals. We analyzed whether patients with a diagnosis of neurolymphomatosis met the 2010 and 2021 CIDP criteria. 152 motor nerves were analyzed, and conduction blocks were found in 13.8% of them. Eight patients (34.7%) demonstrated at least one conduction block. Other demyelinating parameters fulfilling the 2021 CIDP criteria were rare, including reduced conduction velocities (1.7%), prolonged distal motor latencies (3%), absent F-waves (12.4%), and prolonged F-wave latencies (7.7%). Five patients met the 2010 CIDP criteria, whereas only one met the 2021 CIDP criteria. Demyelinating features are rare in neurolymphomatosis, and a conduction block is the most frequent abnormality. Consequently, only one patient met the 2021 criteria for CIDP diagnosis. This is likely attributable to the inclusion of sensory criteria. Furthermore, the new criteria emphasize the importance of identifying red flags, such as pain or monoclonal gammopathy, which could suggest an alternative diagnosis to CIDP. Clinicians should consider neurolymphomatosis in patients who present with red flags or atypical CIDP.

Prolonged Median Motor Distal Latency: What If not Carpal Tunnel Syndrome but Acute Inflammatory Demyelinating Polyradiculoneuropathy?

ABSTRACT Introduction: The wrist is the only segment where both sensory and motor conduction of the same nerve can be studied through routine nerve conduction studies. This study aims to evaluate how two diseases with different pathophysiologies, carpal tunnel syndrome (CTS) and acute inflammatory demyelinating polyradiculoneuropathy (AIDP), differ in terms of median nerve conduction at the wrist. Materials and Methods: Patients hospitalized and diagnosed as having Guillain–Barré syndrome between 2013 and 2021 were screened from the hospital database. Electrodiagnostic subtype classification was performed according to the Rajabally criteria, retrospectively. Patients with AIDP along with age-matched patients with CTS were re-evaluated. Only the data of patients with prolonged median motor distal latency (≥4.0 ms) were included and analyzed. Results: The motor distal latencies recorded in patients with AIDP were significantly more prolonged and the compound muscle action potential amplitudes were significantly lower than those with CTS (P ≤ 0.001). Among the recordable sensory responses, hands with AIDP revealed significantly lower sensory nerve action potential amplitudes than hands with CTS (P ≤ 0.001) although their peak latencies were shorter (P ≤ 0.001) and conduction velocities were faster (P ≤ 0.001). The motor distal latency of the median nerve in patients with AIDP was not correlated with the sensory peak latency, unlike in patients with CTS. Conclusion: Median nerve sensory response, if present, tends to conduct faster in AIDP compared with CTS although the motor distal latency is profoundly prolonged.

The difference in nerve ultrasound and motor nerve conduction studies between autoimmune nodopathy and chronic inflammatory demyelinating polyneuropathy.

Nerve enlargement has been described in autoimmune nodopathy and chronic inflammatory demyelinating polyneuropathy (CIDP). However, comparisons of the distribution of enlargement between autoimmune nodopathy and CIDP have not been well characterized. To fill this gap, we explored differences in the ultrasonographic and electrophysiological features between autoimmune nodopathy and CIDP. Between March 2015 and June 2023, patients fulfilling diagnostic criteria for CIDP were enrolled; among them, those with positive antibodies against nodal-paranodal cell-adhesion molecules were distinguished as autoimmune nodopathy. Nerve ultrasound and nerve conduction studies (NCS) were performed. Overall, 114 CIDP patients and 13 patients with autoimmune nodopathy were recruited. Cross-sectional areas (CSA) at all sites were larger in patients with CIDP and autoimmune nodopathy than in healthy controls. CSAs at the roots and trunks of the brachial plexus were significantly larger in patients with anti-neurofascin-155 (NF155), anti-contactin-1 (CNTN1), and anti-contactin-associated protein 1 (CASPR1) antibodies than in CIDP patients. The patients with anti-NF186 antibody did not have enlargement in the brachial plexus. NCS showed more frequent probable conduction block at Erb's point in autoimmune nodopathy than in CIDP (61.9% vs. 36.6% for median nerve, 52.4% vs. 39.5% for ulnar nerve). Markedly prolonged distal motor latencies were also present in autoimmune nodopathy. Patients with autoimmune nodopathies had distinct distributions of peripheral nerve enlargement revealed by ultrasound, as well as distinct NCS patterns, which were different from CIDP. This suggests the potential utility of nerve ultrasound and NCS to supplement clinical characteristics for distinguishing nodopathies from CIDP.

Recurrent Right-side Bell’s Palsy in Association with Neurovascular Cross-compression: A Case Report

Introduction: Bell’s palsy is a lower motor neuron (LMN) palsy that affects the facial nerve (CN VII) and causes weakness or paralysis of the facial muscles. It can be associated with various causes, including neurovascular cross-compression (NVCC). This case report highlights the challenges in treating recurrent Bell’s palsy caused by NVCC and the need for a multidisciplinary approach. Case report: A 17-year-old girl presented with recurrent right-side Bell’s palsy along with NVCC involving the right and left anterior inferior cerebellar artery forming a loop around the VII and VIII cranial nerve complex. Motor Nerve Conduction Studies (NCS) indicated a right-side facial nerve lesion with prolonged distal latency. Discussion: Despite prior physiotherapy sessions, which proved effective, the patient showed no improvement after five sessions, leading to further investigations. This case also underscores the diagnostic and therapeutic complexities associated with NVCC-induced Bell’s palsy, which emphasizes the urgency of quick diagnosis and intervention to prevent functional limitations. Conclusion: Continued research and advancements in diagnostic and therapeutic modalities are required for better outcomes and improving the quality of life in such patients, particularly in such cases.

Unique clinical and electrophysiological features in the peripheral nerve system in patients with sialidosis – a case series study

BackgroundTo investigate the peripheral nervous system involvement in S sialidosis with typical features of myoclonus, seizure, and giant waves in somatosensory evoked potentials suggesting hyperexcitability in the central nervous system.MethodsThe clinical presentation of patients with genetically confirmed sialidosis was recorded. Neurophysiological studies, including nerve conduction studies (NCSs), F-wave studies, and needle electromyography (EMG), were performed on these patients.ResultsSix patients (M/F: 2:4) were recruited. In addition to the classical presentation, intermittent painful paresthesia was noted in four patients, and three of whom reported it as the earliest symptom. In the NCSs, one patient had reduced compound muscle action potential amplitudes in the right ulnar nerve, while another patient had prolonged distal motor latency in the bilateral tibial and peroneal nerves. Prolonged F-wave latency (83.3%), repeater F-waves (50%), and neurogenic polyphasic waves in EMG (in 2 out of 3 examined patients) were also noted. Interestingly, a very late response was noted in the F-wave study of all patients, probably indicating lesions involving the proximal peripheral nerve or spinal cord.ConclusionIn addition to the central nervous system, the peripheral nervous system is also involved in sialidosis, with corresponding clinical symptoms. Further study on these phenomena is indicated.

Anti-Myelin-associated Glycoprotein Neuropathy

Anti-myelin-associated glycoprotein (MAG) neuropathy, which occurs secondary to immunoglobulin (Ig)M paraproteinemia such as monoclonal gammopathy of undetermined significance, is characterized by slow progression, sensory or sensorimotor disturbances, and ataxia. The estimated prevalence of this neuropathy in Japan is 0.28 per 100,000 population with male preponderance. This neuropathy is diagnosed based on the detection of M protein and anti-MAG antibodies in patients' serum. Nerve conduction studies show prolonged distal latency, and histopathological evaluation of sural nerve biopsies shows widely spaced myelin on electron microscopy. Usually, immunotherapy, including administration of intravenous Ig and corticosteroids, is ineffective, and rituximab is beneficial in approximately 50% of patients. Novel therapies, such as administration of Bruton's tyrosine kinase inhibitors are expected to benefit patients with the MYD88L265P mutation.

Electrophysiological variations of Guillain-Barre syndrome in Bangladesh- Hospital based study

Introduction: Guillain-Barre syndrome (GBS) is an immune mediated disorder of peripheral nerves which usually presents by rapidly evolving ascending weakness &amp; mild sensory loss and hypo- or areflexia. Electrodiagnostic study (EDS) is the basis for classification of different subtypes of the disease. EDS also has a crucial role in diagnosis, ruling out of some differential diagnosis like myopathic and motor neuron disorders and confirming the neuropathic nature of GBS. The benefit of immunotherapy is greatest when introduced early. In addition, electrophysiological characteristic can predict the prognosis of patients with GBS. This study was conducted to determine the predominant subtype and electrophysiological pattern of GBS in the context of Bangladesh. Objectives: Objective of this study was to compare the electrophysiological variations among different electrophysiological subtypes of GBS. Methods: It is an observational cross sectional study conducted in Department of Medicine and Neurology, Sir Salimullah Medical College &amp; Mitford Hospital and National Institute of Neuroscience (NINS), Dhaka, over a period of one year &amp; four months. Total 30 patients were selected by purposive sampling technique. Demographic data were collected from the patients and recorded in structured case report form. Clinical examination and relevant investigations were done meticulously. Collected questionnaire were checked to identify any error in data. Data was analyzed with SPSS version 21 software. Result: In this study, maximum numbers of patients 53% were between 21-30 years of age group with mean value 27.47±8.1 years. Male to female ratio was 1.7:1. Frequency of Guillain-Barre syndrome is predominance at middle age group. Commonest presentation was limb weakness (parapledgia or quadripledgia) in 60% patients, paresthesias &amp; numbness (40%), pain (100%) and deviation of mouth (63%) of GBS patients. Cerebrospinal fluid shows a mild pleocytosis (5 to 50 cells/µl) in majority of cases was found in 76% of patients. Whereas elevated CSF Protein (&gt;45 mg/dl) was seen in all GBS patient. Increased distal motor latency (DML) was found in 93% patients, whereas 7% patients had normal DML. In the case of the lower limbs, increased distal motor latency was predominant. Decreased amplitude of sensory nerve action potential (SNAP) was seen in 83% patients while 16% patients had normal. Slowing of motor conduction velocities, decreased amplitude as well as increase in distal motor latencies were observed, being more pronounced in the lower limbs. F-wave was completely absent in 20.0% patients while 20% patients showed decreased conduction velocity with prolonged latency. Sensory nerve action potential revealed that decreased sensory conduction velocity (SCV) was seen in 26%, absent SCV in 10% and normal SCV in 63% patients. Present study demonstrated that Acute inflammatory demyelinating polyneuropathy (AIDP) was the commonest type of Guillain-Barré syndrome, present in 56% of patient. Around 30% of the patients belonged to acute motor axonal polyneuropathy (AMAN) and 13% were acute motor sensory axonal polyneuropathy (AMSAN). Conclusion: In this study AIDP was the most frequent subtype. The characteristic findings supportive of AIDP include prolonged distal motor latencies, reduced conduction velocities, conduction blocks at non-entrapment sites, temporal dispersion and prolonged F wave latencies. J MEDICINE 2024; 25: 11-16

Proximal median nerve neuropathy: electrodiagnostic and ultrasound findings in 62 patients.

Proximal median nerve (PMN) neuropathies are caused by lesions proximal to the carpal tunnel, which include the forearm, elbow, upper arm, and brachial plexus. Differentiating between carpal tunnel syndrome and PMN neuropathies is important to guide management and is based on clinical, electrodiagnostic (EDX), and ultrasound (US) findings. This study describes the clinical, EDX, and US features in 62 patients with PMNs. All patients underwent EDX studies, and 52 (83.9%) had a US study. The patients were assigned to one of the following four localization zones of PMN neuropathies based on clinical and EDX criteria: Zone 1: extends from the fascicles in the brachial plexus contributing to the median nerve to the innervation of the pronator teres (PT); Zone 2: distal to the branch to the PT and proximal to the origin of the anterior interosseous nerve (AIN); Zone 3: involves the origin of the AIN; and Zone 4: distal to the origin of the AIN and proximal to the carpal tunnel. The localization was based on the pattern of muscle weakness, topography of EMG abnormalities, and US study findings. The anatomical locations of the PMN neuropathies based on clinical, EDX, and US findings were as follows: Zone 1 in 38 patients (61.3%), Zone 2 in 6 patients (9.7%), Zone 3 in 7 patients (11.3%), and Zone 4 in 11 patients (17.7%). The most common etiology among all 62 patients was iatrogenic injury (30 [48.4%]), followed by non-iatrogenic trauma (20 [32.2%]). The following EDX findings were noted: prolonged distal motor latency (29 [46.8%]), decreased motor nerve conduction velocity in the forearm (22 [35.5%]), low amplitude or absent compound muscle action potentials (50 [80.6%]), and abnormal or absent sensory nerve action potentials (50 [80.6%]). Of the 52 (83.9%) patients who underwent US studies, a total of 22 (42.3%) patients showed an increased cross-sectional area of the median nerve. A neuroma was observed in 9 patients (17.4%). It is often possible to localize the site of the median nerve involvement and gain insight into the underlying cause based on clinical and EMG findings, but in certain cases, a US study may be necessary to confirm the location.

Neuropathy caused by pesticide exposure on farmers in Ngablak District, Magelang, Central Java, Indonesia: An electroneuromyography study

Uncontrolled and unsafe use of pesticides can lead to acute and chronic toxicity in farmers, with neuropathy being one of the most common symptoms of chronic toxicity. However, the effects of this toxicity on farmers' electroneuromyography (ENMG) are still unclear. To address this, we conducted a cross-sectional study from July to October 2017 in Ngablak District, Magelang, Central Java, Indonesia. Eligible farmers who were exposed to pesticides underwent electrophysiology examinations, as well as additional tests such as physical examination and laboratory testing. We collected general information such as age and work history by interview. In total, 64 farmers were included in this study. Out of these, 44 farmers were found to have polyneuropathy, with 41 of them having motor polyneuropathy and 19 of them having sensory polyneuropathy. Our findings showed that low blood cholinesterase was associated with distal latency prolongation (p-value: 0.014). The group exposed to organophosphate/carbamate pesticides was also significantly associated with prolonged distal latency (p-value: 0.012). However, motor polyneuropathy was significantly associated with chronic exposure to organophosphate/carbamate pesticides (p-value: 0.009) and not with low blood cholinesterase levels (p-value: 0.454). The study concludes that chronic exposure to organophosphate or carbamate pesticides could result in polyneuropathy disease, particularly in the motor system.

Nerve excitability test and lead toxicity: a case-control study

BackgroundAlthough conventional electrophysiological parameters have been proposed as clinical indicators for monitoring lead neuropathies, their correlations with blood lead level are weak. In this study, we investigated the applicability of nerve excitability tests (NETs) to evaluate lead intoxication.MethodsFourteen workers who were exposed to lead with an elevated blood level ranging from 17.8 to 64.9 µg/dL and 20 healthy controls with similar ages and body heights were enrolled. Both workers and controls underwent nerve conduction studies (NCSs), motor evoked potentials (MEPs) with transcranial magnetic stimulation (TMS), and NETs.ResultsNCSs showed prolonged distal latencies and decreased motor nerve conduction velocity of median nerves in the workers but without significant correlation to blood lead level (BLL). Significantly prolonged MEP latency was observed in the workers (+ 6 ms). NETs demonstrated hyperpolarized resting membrane potentials in stimulus-response curves and changes in the property of potassium channels under a hyperpolarized current in threshold electrotonus, implying that lead hyperpolarized nerves by interfering with potassium channels. NETs also showed a better correlation with BLL than conventional electrophysiological parameters.ConclusionsAxonal hyperpolarization and central conduction delay are more apparently reflecting elevated BLL than NCS. NET may have the potential for early detection of lead neuropathy.

Recurrent motor branch neuropathy in carpal tunnel syndrome: An ultrasound study.

The reason for the variable rate of progression of patients with carpal tunnel syndrome (CTS) to thenar muscles impairment is not fully understood. The aim of this study was to evaluate the occurrence of ultrasound signs of recurrent motor branch (RMB) neuropathy in patients with CTS and to correlate imaging findings with clinical and electrophysiological data. Two cohorts were recruited, one consisting of CTS patients with electrodiagnostic evidence of prolonged median distal motor latency from wrist to thenar eminence and another consisting of sex- and age-matched healthy controls. Ultrasound reliability of RMB measurement was assessed by the calculation of the interclass correlation coefficient (ICC). Patients were evaluated with electrodiagnostic tests and asked to complete the Boston Carpal Tunnel Questionnaire. The difference between the RMB diameter in patients and controls was analyzed using a t test. Correlations between RMB diameter and other parameters were assessed using linear mixed models. 46 hands from 32 patients with CTS and 50 hands from 50 controls were evaluated. The intra- and interobserver agreements in RMB measurement were very good (ICC = 0.84; 95% confidence interval [CI], 0.75 to 0.90) and good (ICC = 0.79; 95% CI, 0.69 to 0.87). The RMB diameter was significantly larger in patients than in controls (P < .0001). No significant correlation was found between the RMB diameter and other variables, except for BMI and median nerve cross-sectional area. Ultrasound is reliable in identifying the RMB and characterizing its abnormalities. In this patient cohort, ultrasound allowed for detection of definite signs of RMB compression neuropathy.

Motor Nerve Conduction Slowing in Amyotrophic Lateral Sclerosis (P10-8.006)

<h3>Objective:</h3> To determine the range of conduction values for motor nerve conduction slowing and further characterize the distribution of conduction slowing in ALS and characterize the limits of conduction slowing beyond which the diagnosis of ALS is uncertain. <h3>Background:</h3> Abnormal motor nerve conduction studies in ALS are attributed to loss of large axons and distal axonopathy, however conduction slowing can be the result of superimposed demyelinating polyneuropathy or an alternate diagnosis. <h3>Design/Methods:</h3> The electrodiagnostic data of 76 chronic inflammatory demyelinating polyneuropathy (CIDP) patients, identified using AAN research criteria was used to create 12 novel equations using regression analysis that determine a range of the expected slowing of a primary demyelinating polyneuropathy. Demyelinating range confidence intervals were defined by assessing conduction velocity (CV), distal latency (DL), and F latency in relation to distal compound muscle action potential (CMAP) amplitude of median, ulnar, fibular, and tibial nerves. Results were then validated in 38 additional CIDP patients. These developed equations were then used to evaluate conduction slowing in 95 patients with ALS. Transformed CMAP amplitude was used as an independent variable whereas transformed DL, CV, and F were used as dependent variables. <h3>Results:</h3> CV slowing, prolonged DL, and abnormal F latency were observed respectively in 22.2%, 19.6%, and 46.7% of the studied nerves. When slowing occurred, it affected more than one segment of the motor nerve, suggesting that loss of large axons is the main mechanism of slowing. No ALS patient had more than 2 nerves with CV slowing in the confidence interval defined by the regression equations or the American Academy of Neurology (AAN) research criteria for CIDP diagnosis. <h3>Conclusions:</h3> The presence of more than two motor nerves with CV slowing in the demyelinating range defined by the regression analysis or AAN criteria in ALS patients suggests an alternative diagnosis or superimposed demyelination. <b>Disclosure:</b> Mr. Mandava has nothing to disclose. Miss Shaikh has nothing to disclose. Mr. Jaffry has nothing to disclose. Mr. Jaffry has nothing to disclose. Mr. Ors has nothing to disclose. Mr. Trivedi has nothing to disclose. Ms. Faiz has nothing to disclose. Mr. Gandhi has nothing to disclose. Dr. Patel has nothing to disclose. Abu Nasar, MD has nothing to disclose. Ankit Pahwa has nothing to disclose. Dr. Sander has received personal compensation for serving as an employee of Grifols. Dr. Sander has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Grifols. Dr. Sander has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for Law firm. Dr. Souayah has received publishing royalties from a publication relating to health care.

An Atypical Presentation of Immune-mediated, Demyelinating Polyneuropathy with Multiple Antibodies to Nerve and Myelin Proteins Following SARS-CoV2 mRNA Vaccination (P10-5.009)

<h3>Objective:</h3> This case describes an atypical demyelinating polyneuropathy temporally associated with SARS-CoV2 mRNA vaccination and characterized by the presence of multiple co-existing autoantibodies. <h3>Background:</h3> A 62-year-old woman developed distal, symmetric upper and lower extremity sensorimotor impairments and areflexia three weeks after SARS-CoV2 booster vaccination (Pfizer-BioNTech). Initial cerebrospinal fluid analysis demonstrated cytoalbuminologic dissociation (protein 76mg/dL). Intravenous immunoglobulin (IVIg) (2 gm/kg total) was prescribed. The patient’s symptoms and signs resolved. Asymmetric, proximal appendicular weakness, distal appendicular sensory loss, gait impairment, and areflexia reoccurred approximately one week later. Plasma exchange (PLEX) was completed, resulting in marked clinical improvement. Clinical worsening again reoccurred in the weeks following PLEX completion. Electrodiagnostic and serologic studies were obtained. Immunomodulatory therapies were escalated with IVIg (repeat 2 gm/kg), corticosteroid, and rituximab therapies prescribed. Sustained symptom improvement was evidenced. <h3>Design/Methods:</h3> Case report with literature review. <h3>Results:</h3> Nerve conduction and electromyography studies demonstrated absent F-waves, prolonged distal motor latencies, and reduced recruitment of normal motor units consistent with a demyelinating polyneuropathy. Ga1NAc-GD1a IgG, beta-tubulin IgG, and neurofascin-155 IgG antibodies were detected in serum samples obtained prior to IVIg therapy (Washington University Neuromuscular Laboratory Demyelinating Neuropathy Panel). <h3>Conclusions:</h3> The patient’s clinical syndrome was ultimately consistent with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The asymmetric pattern of weakness, robust initial treatment response(s), and severe fluctuations were atypical for classical CIDP, but consistent with demyelinating disease marked by specific autoantibodies. Uniquely, Ga1NAc-GD1a IgG, beta-tubulin IgG, and neurofascin-155 IgG antibodies were identified. Antibodies against axons and myelin proteins have been recently reported in patients with acute and chronic demyelinating polyneuropathies. Antibodies to neurofascin isoforms, anti-tubulin and Ga1NAc-GD1a can result in severe phenotypes with variable treatment responses, including robust treatment response to B-cell targeted therapies. To our knowledge, this is a novel case due to multiple co-existing, potentially pathogenic, autoantibodies. A possible immune-mediated mechanism precipitated by SARS-CoV2 vaccination requires further investigation. <b>Disclosure:</b> Dr. Saban has nothing to disclose. Dr. Leech has nothing to disclose. Dr. Carlson has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Medscape. Dr. Carlson has received research support from Horizon Therapeutics. Dr. Carlson has a non-compensated relationship as a Health Service Subcommittee Member with American Academy of Neurology that is relevant to AAN interests or activities. Dr. Sauer has nothing to disclose. The institution of Dr. Ragole has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Alexion Pharmaceuticals. The institution of Dr. Ragole has received personal compensation in the range of $500-$4,999 for serving as a Consultant for UCB. Dr. Ragole has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alexion Pharmaceuticals. The institution of Dr. Ragole has received research support from Alexion Pharmaceuticals.

Appearance of F-wave during electrophysiological study of

To evaluate the appearance of F-wave in patients with carpal tunnel syndrome through electrophysiological study. Fifty patients with carpal tunnel syndrome(CTS) of the median nerve who were diagnosed clinically and through electrophysiological study for median and ulnar nerve. Fifty normal subjects of healthy volunteers of similar age and gender were compared to the patients and examined for nerve conduction study. Nerve conduction study for median and ulnar nerve (motor and sensory) were done for each patient and subject in neurophysiology department to study the distal motor and sensory latency (DML,DSL), compound motor and sensory action potentials (CMAP,SNAP) ,motor and sensory nerve conduction velocities (MNCV,SNCV) and F-wave latencies(maximum, mean and minimum). There are prolonged distal motor and sensory latency, decrease of compound motor and sensory action potential, decrease of motor and sensory nerve conduction velocity and prolongation of F-wave latencies( minimum, mean and maximum.) of the median nerve (motor) in carpal tunnel syndrome patients compared with the controls and these differences are statistically significant p-value &lt; 0.01. The F-wave parameters for median nerve must be added in electrophysiological study to establish the diagnosis of carpal tunnel syndrome.

Clinical and Electrophysiological Characteristics of Very Early Guillain-Barré Syndrome.

This study compared the clinical and electrodiagnostic (EDX) features and long-term outcomes of patients with very early Guillain-Barré syndrome (VEGBS, duration of illness ≤4 days) and those with early/late (>4 days)-presenting GBS. One hundred patients with GBS were clinically evaluated and categorized into VEGBS and early/late GBS groups. Electrodiagnostic studies were performed on the bilateral median, ulnar, and fibular motor nerves and the bilateral median, ulnar, and sural sensory nerves. Admission and peak disability were assessed using the 0 to 6 Guillain-Barré Syndrome Disability Scale (GBSDS). The primary outcome was disability at 6 months, which was categorized as complete (GBSDS ≤1) or poor (GBSDS ≥2). The secondary outcomes were frequencies of abnormal electrodiagnostic findings, in-hospital progression, and mechanical ventilation (MV). Patients with VEGBS had higher peak disability (median 5 vs. 4; P = 0.02), frequent in-hospital disease progression (42.9% vs. 19.0%, P < 0.01), needed MV (50% vs. 22.4%; P < 0.01), and less frequent albuminocytologic dissociation (52.4% vs. 74.1%; P = 0.02) than those with early/late GBS. Thirteen patients were lost to follow-up at 6 months (nine patients with VEGBS and four patients with early/late GBS). The proportion of patients with complete recovery at 6 months was comparable (60.6% vs. 77.8%; P = ns ). Reduced d-CMAP was the most common abnormality, noted in 64.7% and 71.6% of patients with VEGBS and early/late GBS, respectively ( P = ns). Prolonged distal motor latency (≥130%) was more common in early/late GBS than in VEGBS (36.2% vs. 25.4%; P = 0.02), whereas absent F-waves were more frequent in VEGBS (37.7% vs. 28.7%; P = 0.03). Patients with VEGBS were more disabled at admission than those with early/late GBS. However, 6 month's outcomes were similar between the groups. F-wave abnormalities were frequent in VEGBS, and distal motor latency prolongation was common in early/late GBS.

Clinical, laboratory, and electrophysiological presentations and treatment modalities in Guillain–Barré syndrome: A prospective study

INTRODUCTION: Guillain–Barré syndrome (GBS) is a rare autoimmune disorder causing acute inflammatory demyelinating polyneuropathy (AIDP), leading to muscle weakness, paralysis, and respiratory failure. MATERIALS AND METHODS: This single-center, prospective study was performed in the department of medicine of a tertiary care institute over a period of 18 months with 6 months of follow-up. This study enrolled 50 patients diagnosed with GBS. We analyzed medical records, clinical presentation, laboratory results, electrophysiological findings, and treatment modalities. RESULTS: This study enrolled 50 patients diagnosed with GBS, the mean age of patients was 38.5 ± 17.02 years, and males were predominant (70%). Quadriparesis was the most common motor complaint presented in 80%, whereas tingling and numbness were the most common sensory complaint (70%); 4% of patients had bowel and bladder involvement. Excessive sweating was the most common autonomic disorder, found in 44 (88%) patients. In a nerve conduction study, AIDP was the most common subtype seen in 28 (56%) patients; acute motor axonal neuropathy (AMAN) and acute motor sensory axonal neuropathy (AMSAN) were seen in 11 (22%) patients each. In patients with AIDP, distal latency prolongation was the most common findings (86%), while in AMAN and AMSAN, a decrease in CAMP was the most prevalent finding. Ventilatory support was needed in 18 (36%) patients enrolled in the study. Mortality was reported in 8 (16%) patients. In AMAN-AMSAN variants, IV Ig therapy appeared to have better outcomes at 6 months as compared to plasma exchange therapy. CONCLUSION: This study provides valuable insights into the clinical, laboratory, and electrophysiological features of GBS and highlights the effectiveness of IVIG as a treatment modality. Early recognition and treatment are crucial for optimal outcomes in GBS patients.

Electrophysiologic Characteristics of Nitrous-Oxide-Associated Peripheral Neuropathy: A Retrospective Study of 76 Patients

The electrophysiologic characteristics of peripheral neuropathy secondary to nitrous oxide (N2O) abuse remain unclear. The paper therefore aimed to summarize the electrophysiologic characteristics of N2O-associated peripheral neuropathy and identify the risk factors of severe nerve injury. The electrophysiologic results and clinical data of patients with peripheral neuropathy secondary to N2O abuse at our hospital between 2018 and 2020 were analyzed retrospectively, and their electrophysiologic changes were summarized. Most patients exhibited decreased sensory and motor nerve conduction velocities (75% and 76%), decreased sensory nerve and compound motor action potentials (57% and 59%), and prolonged distal motor latency (59%), while a response was absent in 36%. These findings indicate that N2O abuse can result in generalized injury to sensory and motor nerves. Electrophysiologic results indicated axonal neuropathy in 37 cases (49%), demyelinating peripheral neuropathy in 4 (5%), and mixed neuropathy in 12 (16%). Peripheral nerve injury was more common in the lower limbs (72%) than in the upper limbs (42%, p<0.0001). The upper and lower limbs were primarily affected by sensory nerve demyelination (35%) and motor axonal injury (67%), respectively. Subgroup analysis indicated that longer N2O exposure and longer disease course were associated with more-severe motor axonal injury in the lower limbs. N2O-associated peripheral neuropathy can lead to sensory and motor nerve injury, with axonal injury being the most common. Injuries were more severe in the lower limbs. Prolonged N2O exposure and disease course increased the severity of motor axonal injury in the lower limbs.

Young infants with PMP22 duplication can have minor nerve conduction study abnormalities

Charcot-Marie-Tooth disease type 1A (CMT1A) is related to PMP22 gene duplication. It is characterized at electrodiagnostic testing (EDX) by diffuse homogeneous signs of demyelination, such as velocity slowing and prolonged distal latencies. These abnormalities are less pronounced in infants under two years old, and the possibility of normal nerve conduction studies (NCS) in infants with CMT1A under one year of age has been questioned. We report three infants who displayed normal or almost normal NCS. EDX abnormalities in CMT1A patients may therefore appear late during development. This may affect early EDX diagnosis in infants and should be considered for upcoming clinical trials.

HP38: Neurophysiological assessment of peripheral neuropathies associated with COVID-19

Neurological complications associated with COVID-19 are a significant cause of morbidity, affecting both central and peripheral nervous systems. We aim to assess the electrophysiological features of peripheral nerve injuries (PNI) in patients with COVID-19.Methods: We included 31 patients between March 2020 and April 2021 with a suspected diagnosis of PNI with COVID-19. We performed motor and sensory nerve conduction studies and electromyography (EMG) in the upper and lower extremities.Results: The mean age was 66.8±3.1 years (21 males, 10 females). A 96.7% (30 patients) were admitted to ICU, with a mean stay of 32.9±5.1 days. The neurophysiological examination showed, in descending order: mixed polyneuropathies 22.6% (7 patients), motor axonal polyneuropathies 19.4% (6 patients), sensorimotor axonal polyneuropathies 19.4% (6 patients), peroneal mononeuropathies 12.9% (4 patients), brachial plexopathies 12.9% (4 patients), Guillain-Barré syndrome (GBS) 6.4% (2 patients), Miller Fisher syndrome (MFS) 3.2% (1 patient) and femoral mononeuropathy 3.2% (1 patient).The low amplitude in both motor and sensory conduction studies was the most common neurophysiological finding except in GBS and MFS that showed prolonged distal latency and slow conduction velocity. EMG showed spontaneous activity in all patients.Conclusion: Our study shows the main neuropathy damage related to COVID-19 was critical illness polyneuropathy; however, we must consider mononeuropathies in these patients. There is broad evidence concerning the peripheral nervous system injury as a complication in patients hospitalized by COVID-19, being the neurophysiological tests a valuable tool to assess the peripheral nerve function.