The sural-sparing pattern in clinical variants and electrophysiological subtypes of Guillain-Barré syndrome.

BACKGROUND: Guillain-Barré syndrome (GBS) is the most common cause of acute flaccid paralysis worldwide and can be classified into electrophysiological subtypes and clinical variants. OBJECTIVE: This study aimed to compare the frequency of the sural-sparing pattern (SSP) in subtypes and variants of GBS. METHODS: This retrospective cohort study analyzed clinical and electrophysiological data of 171 patients with GBS hospitalized in public and private hospitals of Natal, Rio Grande do Norte, Brazil, between 1994 and 2018; all cases were followed up by the same neurologist in a reference neurology center. Patients were classified according to electrophysiological subtypes and clinical variants, and the SSP frequency was compared in both categories. The exact Fisher test and Bonferroni correction were used for statistical analysis. RESULTS: The SSP was present in 53% (57 of 107) of the patients with acute inflammatory demyelinating polyradiculoneuropathy (AIDP), 8% (4 of 48) of the patients with axonal subtypes, and 31% (5 of 16) of the equivocal cases. The SSP frequency in the AIDP was significantly higher than in the axonal subtypes (p < 0.0001); the value was kept high after serial electrophysiological examinations. Only the paraparetic subtype did not present SSP. CONCLUSION: The SSP may be present in AIDP and axonal subtypes, including acute motor axonal neuropathy, but it is significantly more present in AIDP. Moreover, the clinical variants reflect a specific pathological process and are correlated to its typical electrophysiological subtype, affecting the SSP frequency.

ANTECEDENTES: A síndrome de Guillain-Barré (GBS) é a causa mais comum de paralisia flácida aguda em todo o mundo e pode ser classificada em subtipos eletrofisiológicos e variantes clínicas. OBJETIVO: Este estudo teve como objetivo comparar a frequência do padrão de preservação do sural (SSP) em subtipos e variantes de GBS. MéTODOS: É um estudo de coorte retrospectivo que analisou dados clínicos e eletrofisiológicos de 171 pacientes com GBS internados em hospitais públicos e privados de Natal, Rio Grande do Norte, Brasil, entre 1994 e 2018. Todos os casos foram acompanhados pelo mesmo neurologista em centro de referência em neurologia. Os pacientes foram classificados de acordo com os subtipos eletrofisiológicos e variantes clínicas e a frequência do SSP foi comparada em ambas as categorias. O teste exato de Fisher e a correção de Bonferroni foram utilizados para análise estatística. RESULTADOS: O SSP esteve presente em 53% (57 de 107) dos pacientes com polirradiculoneuropatia desmielinizante inflamatória aguda (PDIA), em 8% (4 de 48) dos pacientes com subtipos axonais e em 31% (5 de 16) dos casos não definidos. A frequência do SSP no AIDP foi significativamente maior do que nos subtipos axonais (p < 0,0001); o valor manteve-se elevado após exames eletrofisiológicos seriados. Apenas o subtipo paraparético não apresentou SSP. CONCLUSãO: O SSP pode estar presente na PDIA e nos subtipos axonais, incluindo a neuropatia axonal motora aguda, mas está significativamente mais presente na PDIA. Além disso, as variantes clínicas refletem um processo patológico específico e estão correlacionadas ao seu subtipo eletrofisiológico típico, afetando a frequência do SSP.

Guillain-Barre syndrome of acute motor axonal neuropathy (AMAN) type associated with herpes zoster: a case report.

Guillain Barre syndrome (GBS) following Varicella zoster is a rare presentation and has only been reported in a few cases around the world. Of the reported cases, the type of GBS is not specified in the majority, and where specified is of the acute inflammatory demyelinating polyradiculoneuropathy (AIDP) type. We report a case of acute motor axonal neuropathy (AMAN) type GBS following herpes zoster in a 27-year-old male who presented with bilateral lower limb weakness and left sided lower motor neuron type facial nerve palsy a week after herpes zoster infection.

Alcohol-related peripheral neuropathy: Clinico-neurophysiological characteristics and diagnostic utility of the neuropathy symptoms score and the neuropathy impairment score.

Alcohol overconsumption is well known to cause damage to the peripheral nervous system, affecting both small and large nerve fibers. The aim of this descriptive study was to investigate peripheral nerve damage, and to correlate clinical, epidemiological and neurophysiological findings, in patients diagnosed with Alcohol Use Disorder (AUD). Ninety alcohol-dependent subjects on inpatient basis were enrolled in this prospective study over a 3-year period. Every subject was assessed by the Neuropathy Symptoms Score (NSS) questionnaire and the Neuropathy Impairment Score (NIS) clinical examination grading scale, followed by Nerve Conduction Studies, Quantitative Sensory Testing and Sympathetic Skin Response (SSR) testing. Peripheral neuropathy was diagnosed in 54 subjects (60%), by abnormal neurophysiological tests and presence of clinical signs or symptoms. Among them, pure large fiber neuropathy (LFN) was found in 18 subjects, pure small fiber neuropathy (SFN) in 12 subjects, and both large and small fiber neuropathy was diagnosed in 24 subjects. Using linear regression, we found that higher NSS and NIS scores correlated with lower amplitudes of the sural sensory nerve action potential and of the SSR. We also found a significant longer duration of alcohol abuse in subjects with neuropathy, using Student's t-test (p = 0.024). Additionally, applying NIS abnormal cut-off score ≥4, using ROC analysis, we predicted the majority of subjects with LFN, confirming 95.23% sensitivity and 93.75% specificity. Our study confirmed that peripheral neuropathy involving large and small nerve fibers, with a symmetrical length-dependent pattern, is common between patients with AUD and related to the duration of the disorder. We suggest that NSS and NIS scales could be used for the assessment of neuropathy in clinical practice, when the essential neurophysiological testing is not available.

Ionic plasmon-polariton in application to neurosignaling.

The diffusive ion current is insufficient to explain the fast saltatory conduction observed in myelinated axons and in pain-sensing C fibers in the human nervous system, where the stimulus signal exhibits a velocity two orders of magnitude greater than the upper limit of ion diffusion velocity, even when the diffusion is accelerated by myelin, as in the discrete cable model including the Hodgkin-Huxley mechanism. The agreement with observations has been achieved in a wave-type model of stimulus signal kinetics via synchronized ion local density oscillations propagating as a wave in axons periodically corrugated by myelin segments in myelinated axons, or by periodically distributed rafts with clusters of Na^{+} channels in C fibers. The resulting so-called plasmon-polariton model for saltatory conduction reveals also the specific role of myelin, which is different from what was previously thought. This can be important for identifying a new target for the future treatment of demyelination diseases.

Reference values for nerve conduction studies of the peroneal, tibial, and sural nerve derived from a large population-based cohort: Associations with demographic and anthropometric characteristics-The Maastricht study.

INTRODUCTION/AIMS: Nerve conduction studies (NCSs) are widely used to support the clinical diagnosis of neuromuscular disorders. The aims of this study were to obtain reference values for peroneal, tibial, and sural NCSs and to examine the associations with demographic and anthropometric factors. METHODS: In 5099 participants (aged 40-79 years) without type 2 diabetes of The Maastricht Study, NCSs of peroneal, tibial, and sural nerves were performed. Values for compound muscle action potential (CMAP) and sensory nerve action potential amplitude, nerve conduction velocity (NCV), and distal latency were acquired. The association of age, sex, body mass index (BMI), and height with NCS values was determined using uni- and multivariate linear regression analyses. RESULTS: Detailed reference values are reported per decade for men and women. Significantly lower NCVs and longer distal latencies were observed in all nerves in older and taller individuals as well as in men. In these groups, amplitudes of the tibial and sural nerves were significantly lower, whereas a lower peroneal nerve CMAP was only significantly associated with age. BMI showed a multidirectional association. After correction for anthropometric factors in the multivariate analysis, the association between sex and NCS values was less straightforward. DISCUSSION: These values from a population-based dataset could be used as a reference for generating normative values. Our findings show the association of NCS values with anthropometric factors. In clinical practice, these factors can be considered when interpreting NCS values.

Computational models of compound nerve action potentials: Efficient filter-based methods to quantify effects of tissue conductivities, conduction distance, and nerve fiber parameters.

BACKGROUND: Peripheral nerve recordings can enhance the efficacy of neurostimulation therapies by providing a feedback signal to adjust stimulation settings for greater efficacy or reduced side effects. Computational models can accelerate the development of interfaces with high signal-to-noise ratio and selective recording. However, validation and tuning of model outputs against in vivo recordings remains computationally prohibitive due to the large number of fibers in a nerve. METHODS: We designed and implemented highly efficient modeling methods for simulating electrically evoked compound nerve action potential (CNAP) signals. The method simulated a subset of fiber diameters present in the nerve using NEURON, interpolated action potential templates across fiber diameters, and filtered the templates with a weighting function derived from fiber-specific conduction velocity and electromagnetic reciprocity outputs of a volume conductor model. We applied the methods to simulate CNAPs from rat cervical vagus nerve. RESULTS: Brute force simulation of a rat vagal CNAP with all 1,759 myelinated and 13,283 unmyelinated fibers in NEURON required 286 and 15,860 CPU hours, respectively, while filtering interpolated templates required 30 and 38 seconds on a desktop computer while maintaining accuracy. Modeled CNAP amplitude could vary by over two orders of magnitude depending on tissue conductivities and cuff opening within experimentally relevant ranges. Conduction distance and fiber diameter distribution also strongly influenced the modeled CNAP amplitude, shape, and latency. Modeled and in vivo signals had comparable shape, amplitude, and latency for myelinated fibers but not for unmyelinated fibers. CONCLUSIONS: Highly efficient methods of modeling neural recordings quantified the large impact that tissue properties, conduction distance, and nerve fiber parameters have on CNAPs. These methods expand the computational accessibility of neural recording models, enable efficient model tuning for validation, and facilitate the design of novel recording interfaces for neurostimulation feedback and understanding physiological systems.

Assessment of diagnostic criteria for multifocal motor neuropathy in patients included in the Italian database.

BACKGROUND AND PURPOSE: This study aimed to assess the diagnostic criteria, ancillary investigations and treatment response using real-life data in multifocal motor neuropathy (MMN) patients. METHODS: Clinical and laboratory data were collected from 110 patients enrolled in the Italian MMN database through a structured questionnaire. Twenty-six patients were excluded due to the unavailability of nerve conduction studies or the presence of clinical signs and symptoms and electrodiagnostic abnormalities inconsistent with the MMN diagnosis. Analyses were conducted on 73 patients with a confirmed MMN diagnosis and 11 patients who did not meet the diagnostic criteria. RESULTS: The European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) diagnostic criteria were variably applied. AUTHOR: When applying the American Association of Electrodiagnostic Medicine criteria, an additional 17% of patients fulfilled the criteria for probable/definite diagnosis whilst a further 9.5% missed the diagnosis. In 17% of the patients only compound muscle action potential amplitude, but not area, was measured and subsequently recorded in the database by the treating physician. Additional investigations, including anti-GM1 immunoglobulin M antibodies, cerebrospinal fluid analysis, nerve ultrasound and magnetic resonance imaging, supported the diagnosis in 46%-83% of the patients. Anti-GM1 immunoglobulin M antibodies and nerve ultrasound demonstrated the highest sensitivity. Additional tests were frequently performed outside the EFNS/PNS guideline recommendations. CONCLUSIONS: This study provides insights into the real-world diagnostic and management strategies for MMN, highlighting the challenges in applying diagnostic criteria.

Values and diagnostic accuracy of sensory nerve action potentials in control participants and participants with diabetes with and without clinical diabetic neuropathy, based on neuropathy scale measurements.

BACKGROUND: The assessment of the normative values of sensory nerve action potentials (SNAP) and their diagnostic accuracies using validated neuropathy-assessment tools to classify participants into groups with and without neuropathy was not previously described in the literature. METHODS: The Utah Early Neuropathy Scale (UENS), Michigan neuropathy-screening instrument, and nerve conduction data were collected prospectively. We described and compared the values of the sural, superficial peroneal sensory (SPS), and superficial radial SNAP amplitude in different age groups for three groups. Group 1 (G1)-control participants (UENS <5), group 2 (G2)-participants with diabetes without clinical diabetic neuropathy (UENS <5), and group 3 (G3)-participants with clinical diabetic neuropathy (UENS ≥5). We also described the diagnostic accuracy of single-nerve amplitude and a combined sensory polyneuropathy index (CSPNI) that consists of four total points (one point for each of the following nerves if their amplitude was <25% lower limit of normal: right sural, left sural, right SPS, and left SPS potentials). RESULTS: We assessed 135 participants, including 41, 37, and 57 participants in G1, G2, and G3, respectively, with age median (interquartile ranges) of 51 (45-56), 47 (38-56), and 54 (51-61) years, respectively, whereas 19 (46.3%), 18 (48.7%), and 32 (56.14%) of them were males, respectively. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) scores were 68.4%, 92.3%, 86.7%, and 80% for the sural amplitude; 86%, 58.3%, 62%, and 84% for the SPS amplitude; 66.7%, 94.4%, 90.5%, and 78.2% for the CSPNI of 3; and 54.4%, 98.6%, 96.9%, and 73.2% for the CSPNI of 4, respectively. CONCLUSION: Sural nerve had a high specificity for neuropathy; however, the CSPNI had the highest specificity and PPV, whereas the SPS had the highest sensitivity and NPV.

Normal Values of Central, Peripheral, and Root Motor Conduction Times in a Healthy Korean Population.

PURPOSE: Central, peripheral, and root motor conduction times (CMCTs, PMCTs, and RMCTs, respectively) are valuable diagnostic tools for spinal cord and motor nerve root lesions. We investigated the normal values and the effects of age and height on each motor conduction time. METHODS: This study included 190 healthy Korean subjects who underwent magnetic stimulation of the cortex and spinous processes at the C7 and L1 levels. Recording muscles were abductor pollicis brevis and abductor digiti minimi in the unilateral upper limb and extensor digitorum brevis and abductor hallucis in the contralateral lower limb. F-wave and compound motor nerve action potentials were also recorded. Central motor conduction time was evaluated as the difference between cortical motor evoked potential onset latency and PMCT using calculation and spinal stimulation methods. Root motor conduction time was computed as the difference between spinal stimulated and calculated CMCTs. RESULTS: The average age and height of the participants were 41.21 ± 14.39 years and 164.64 ± 8.27 cm, respectively; 39.5% (75/190) patients were men. In the linear regression analyses, upper limb CMCTs showed a significant and weak positive relationship with height. Lower limb CMCTs demonstrated a significant and weak positive relationship with age and height. Peripheral motor conduction times were significantly and positively correlated with age and height. Root motor conduction times showed no significant relationship with age and height, except for abductor pollicis brevis-RMCT, which had a weak negative correlation with height. CONCLUSIONS: This study provides normal values of CMCTs, PMCTs, and RCMTs, which have potential clinical applications. When interpreting CMCTs, age and height should be considered.

Upper and lower limb tremor in inflammatory neuropathies.

OBJECTIVE: The mechanisms underlying neuropathic tremor remain incompletely understood and a distinction has not been drawn between proximal and distal neuropathies. Lower limb tremor contributes to imbalance in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), but this is unexplored in other neuropathies. We characterized upper and lower limb tremor in chronic immune sensory polyradiculopathy (CISP) and distal acquired demyelinating neuropathy with anti-MAG antibodies (DADS-MAG), contrasted to CIDP. METHODS: This was a cross-sectional study of 38 patients (CIDP [n = 25], CISP [n = 7], DADS-MAG [n = 6]). Clinical assessment, tremor study recordings, nerve conduction studies, and somatosensory evoked potentials were performed. Balance was measured by force platform. RESULTS: Upper limb tremor was prevalent (CIDP 66%, CISP 70%, DADS-MAG 100%). Peak frequencies followed a gradient along the upper limb, unchanged by weight-loading. Lower limb tremor was also present (CIDP 32%, CISP 29%, DADS-MAG 66%) and associated with imbalance. Nerve conduction parameters correlated with upper limb tremor in DADS-MAG and CISP, and imbalance in CISP. CONCLUSIONS: Upper limb tremor is mediated by peripheral and central mechanisms regardless of distal or proximal pathology. Lower limb tremor correlates with peripheral nerve function and contributes to imbalance. SIGNIFICANCE: This study contributes to the understanding of neuropathic tremor. Addressing lower limb tremor may be of therapeutic importance for neuropathy-associated imbalance.

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.

Impact of 2021 European Academy of Neurology/Peripheral Nerve Society diagnostic criteria on diagnosis and therapy of chronic inflammatory demyelinating polyradiculoneuropathy variants.

BACKGROUND AND PURPOSE: There are different criteria for the diagnosis of different variants of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The 2021 European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) guidelines provide specific clinical criteria for each CIDP variant even if their therapeutical impact has not been investigated. METHODS: We applied the clinical criteria for CIDP variants of the 2021 EAN/PNS guidelines to 369 patients included in the Italian CIDP database who fulfilled the 2021 EAN/PNS electrodiagnostic criteria for CIDP. RESULTS: According to the 2021 EAN/PNS clinical criteria, 245 patients achieved a clinical diagnosis of typical CIDP or CIDP variant (66%). We identified 106 patients with typical CIDP (29%), 62 distal CIDP (17%), 28 multifocal or focal CIDP (7%), four sensory CIDP (1%), 27 sensory-predominant CIDP (7%), 10 motor CIDP (3%), and eight motor-predominant CIDP (2%). Patients with multifocal, distal, and sensory CIDP had milder impairment and symptoms. Patients with multifocal CIDP had less frequently reduced conduction velocity and prolonged F-wave latency and had lower levels of cerebrospinal fluid protein. Patients with distal CIDP more frequently had reduced distal compound muscle action potentials. Patients with motor CIDP did not improve after steroid therapy, whereas those with motor-predominant CIDP did. None of the patients with sensory CIDP responded to steroids, whereas most of those with sensory-predominant CIDP did. CONCLUSIONS: The 2021 EAN/PNS criteria for CIDP allow a better characterization of CIDP variants, permitting their distinction from typical CIDP and more appropriate treatment for patients.

Neuromuscular ultrasound in combination with nerve conduction studies helps identify inflammatory motor neuropathies from lower motor neuron syndromes.

BACKGROUND AND PURPOSE: Identifying patients with inflammatory motor neuropathies (IMNs) is warranted since effective treatments are available and the prognosis of these patients differs from that of amyotrophic lateral sclerosis patients. METHODS: Between January 2019 and May 2022, 102 consecutive treatment-naïve lower motor neuron syndrome (LMNS) patients were recruited; these patients were suspected of having multifocal motor neuropathy, pure motor chronic inflammatory demyelinating polyneuropathy or amyotrophic lateral sclerosis with initial lower motor neuron presentation. Neuromuscular ultrasound (US) and nerve conduction studies (NCSs) were conducted at baseline. Relevant diagnostic investigations were performed if clinically warranted. The proposed US evidence of IMN was as follows: (i) nerve enlargement at ≥1 of the predetermined sites or (ii) absence of high intensity fasciculations in predefined muscle groups. Final diagnoses were made by experienced physicians after a prolonged follow-up period (≥12 months). IMN patients were defined as LMNS patients who experienced convincing improvements in response to immunotherapies. IMN patients without electrodiagnostic demyelinating features were diagnosed with treatment-responsive LMNS (TR-LMNS). RESULTS: In total, 16 patients were classified as IMN, including nine chronic inflammatory demyelinating polyneuropathy/multifocal motor neuropathy patients and seven TR-LMNS patients. Six TR-LMNS patients were identified by neuromuscular US. The sensitivity and specificity of NCSs, nerve US and muscle US were 56.3% and 100%, 43.8% and 90.7% and 68.8% and 97.7%, respectively. When these three modalities were combined, the sensitivity and specificity were 93.8% and 88.4%, respectively. CONCLUSION: Neuromuscular US studies are supplementary modalities to NCSs, and the combined use of these techniques might improve the identification of IMNs in LMNS patients.

Natural evolution of idiopathic carpal tunnel syndrome with respect to wrist and hand anthropometry: A prospective cohort study.

OBJECTIVE: A greater wrist depth/width ratio and wrist depth/palm length ratio are known risk factors for carpal tunnel syndrome. We hypothesized that these parameters might also predict progression in patients who were not surgically treated. METHODS: Seventy-eight patients with moderately severe idiopathic carpal tunnel syndrome of at least 10 months duration at recruitment, who declined surgical treatment and steroid injection, underwent repeated neurophysiological assessments after 3 years. A > 10% increase in median SNAP latency was taken as evidence of significant deterioration. RESULTS: Patients with a wrist ratio ≥ 0.72 showed a statistically significant deterioration in SNAP latency from 5.46 (SD 2.09) to 7.16 (SD 1.56) ms and in SNAP amplitude from 30.19 (SD 13.8) to 16.62 (SD 14.42) µv. For those with a wrist-to-palm ratio ≥ 0.42, SNAP latency deteriorated from 5.27 (SD 1.21) to 7.1 (SD 1.52) ms, and amplitude from 32.78 (SD 13.76) to 19.45 (SD 16.62) µv. Patients with lower ratios did not show significant changes in any neurophysiological parameter. The relative risk of significant deterioration in SNAP latency in patients with a wrist ratio ≥ 0.72 was 2.04 (95% CI 1.27-3.27). CONCLUSION: In untreated idiopathic carpal tunnel syndrome, patients with larger wrist and wrist-to-palm ratios are more likely to show neurophysiological progression.

Anti-cancer therapeutic agents and carpal tunnel syndrome: Clinical, electrodiagnostic, and ultrasound findings in seven patients.

INTRODUCTION: Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy and rarely develops after drug therapy. This study describes the clinical, electrodiagnostic (EDX), and ultrasound (US) findings in seven patients who experienced CTS due to anti-cancer therapeutic agents. METHODS: All patients underwent EDX testing, and four patients had an US study. RESULTS: CTS occurred in four patients with aromatase inhibitors, two with immune checkpoint inhibitors, and one with a selective estrogen receptor modulator. The mean duration between initiation of the anti-cancer therapeutic agents and symptom onset was 6 weeks (range: 2-12 weeks). Decreased digit sensation was noted in all patients; wasting and weakness of the abductor pollicis brevis (APB) was observed in three (42.8%) patients. The compound muscle action potentials (CMAP) of the APB and sensory nerve action potentials of the second or third digit could not be recorded in two (28.5%) and four (57.1%) patients, respectively. The needle EMG detected fibrillations and positive sharp waves in the APB in two patients. The motor unit potentials of the APB were decreased with large polyphasics in three (42.8%) patients. Of the four patients who underwent US testing, all had increased cross-sectional area of the median nerve at the carpal tunnel inlet, three (75%) had thenar muscle atrophy, and two (50%) had a loss of fascicular pattern. Three (42.8%) patients underwent a CTR. CONCLUSIONS: Physicians should be cognizant of the relationship between anti-cancer therapeutic agents and CTS. EDX studies and US play important roles in the diagnostic assessment of such patients.

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.

Provocative changes in nerve conductions: Fact or fiction?

At times electrodiagnostic medical consultants (EMCs) are asked to perform studies in both a neutral position, and then again after the patient is in a provocative position that exacerbates symptoms, to assess for measurable electrophysiologic changes. While this approach might seem initially appealing, particularly when standard studies are not effective at diagnosis, empiric studies in several conditions have been unimpressive. Studies in median neuropathy at the wrist, thoracic outlet syndrome, piriformis syndrome, and radial tunnel syndrome have failed to demonstrate reproducible changes in nerve conduction studies in positions that exacerbate symptoms. Furthermore, there is lack of a plausible pathophysiologic mechanism for producing both measurable and rapidly reversible electrophysiologic changes after just a few minutes, or less, of compression. Axon loss and demyelination would not be rapidly reversible, and positional changes of 2 min or less (the durations generally studied) would be insufficient to produce measurable nerve ischemia. Last, we have gained a greater appreciation for how much nerves move within limbs with changes in joint position; this movement can lead to misleading changes in nerve conduction studies. It is thus appropriate to conclude that testing nerve conduction in provocative or symptomatic positions adds no value to electrodiagnostic testing.

Sympathetic skin response for early detection of type 2 diabetic peripheral neuropathy and nephropathy.

BACKGROUND: Diabetic peripheral neuropathy (DPN) and diabetic nephropathy (DN) are common complications of type 2 diabetes mellitus (T2DM). Although nerve conduction studies (NCS) and sympathetic skin response (SSR) can detect DPN, the more sensitive method for early diagnosis remains unclear. Furthermore, whether DPN can be used as a predictor for diabetic nephropathy needs clarification. METHODS: We evaluated nerve conduction studies, sympathetic skin response, and the diabetic nephropathy indicator microalbuminuria (MAU) in 192 patients with type 2 diabetes mellitus and 50 healthy controls. RESULTS: Patients with type 2 diabetes mellitus showed a lower sensory nerve conduction velocity (SCV), sensory active nerve potential (SNAP), motor nerve conduction velocity (MCV), and compound motor action potential (CMAP) than the controls on NCS. Abnormal rates for nerve conduction studies and sympathetic skin response were 75.0% and 83.3%, respectively, in patients with type 2 diabetes mellitus. Interestingly, 54.2% of patients with normal nerve conduction studies had an abnormal sympathetic skin response. Moreover, we found a positive correlation between sympathetic skin response and microalbuminuria for the first time. The abnormal rate of microalbuminuria was 53.8%, lower than that of abnormal nerve conduction studies or sympathetic skin response patients. CONCLUSION: Sympathetic skin response is a more sensitive method than nerve conduction studies for the early diagnosis of diabetic peripheral neuropathy. Abnormal sympathetic skin response might serve as an indicator for early diabetic nephropathy. Additionally, diabetic peripheral neuropathy may occur earlier than diabetic nephropathy in the development of type 2 diabetes mellitus.