Utility of single fibre electromyography (SFEMG)and motor unit number estimation technique (MUNE) in the diagnosis and differentiation of polyneuropathies of different aetiology.

OBJECTIVE: To determine whether single fibre electromyography and motor unit number index can distinguish between axonal and myelin lesions in polyneuropathies. METHODS: This case-control study was conducted at the Department of Medical Physiology, School of Medicine, University of Duhok, Iraq, and the Neurophysiology Department, Hawler Teaching Hospital, Erbil, Iraq, from January 2021 to March 2022. Group A had patients diagnosed with polyneuropathy regardless of the aetiology, while group B had age-matched healthy controls. Both groups were subjected to single fibre electromyography and motor unit number index as well as conventional nerve conduction study and concentric needle electromyography. Data was analysed using SPSS 26. RESULTS: Of the 140 subjects, 60(43%) were patients in group A; 40(67%) males and 20(33%) females with mean age 55.3±7.2 years. There were 80(57%) controls in group B; 43(54%) females and 37(46%) males with mean age 53.81±7.15. Group A had significantly higher single fibre electromyography jitter, and mean consecutive difference (MCD) values than group B (p<0.05). Group A patients with axonal polyneuropathy had a higher mean jitter (MCD) value (36.476.7ms) than those with demyelinating polyneuropathy (23.262.31 ms) (P <0.05). Patients in group A had a motor unit number index value with a significantly lower mean value (p<0.05) when compared to the controls. Axonal polyneuropathy patients had a lower MUNIX value (99.612.8) than demyelinating polyneuropathy patients (149.845.7) (P< 0.05). CONCLUSIONS: Single fibre electromyography and motor unit number index could help differentiate between the pathophysiology of axonal and demyelinating polyneuropathy.

[Multifocal Motor Neuropathy].

Multifocal motor neuropathy (MMN), an acquired chronic progressive immune-mediated motor neuropathy, is characterized by asymmetrical distal upper limb muscle weakness and muscle atrophy without sensory impairment. Differentiation from amyotrophic lateral sclerosis is usually challenging, and electrophysiological studies show multifocal conduction blocks. Immunoglobulin (Ig)M GM1 antibodies are detected in approximately 50% of patients. In contrast to chronic inflammatory demyelinating polyneuropathy, corticosteroids are ineffective for management of MMN, and IVIg is the sole established treatment.

Electrophysiological grading scale for polyneuropathy severity.

OBJECTIVE: To establish a simple electrophysiological scale for patients with distal symmetric axonal polyneuropathy, in order to promote standardized and informative electrodiagnostic reporting, and understand the complex relationship between electrophysiological and clinical polyneuropathy severity. METHODS: We included 76 patients with distal symmetric axonal polyneuropathy, from a cohort of 151 patients with polyneuropathy prospectively recruited from November 2016 to May 2017. Patients underwent nerve conduction studies (NCS), were evaluated by the Toronto Clinical Neuropathy Score (TCNS), and additional tests. The number of abnormal NCS parameters was determined, within the range of 0-4, considering low amplitude or conduction velocity in the sural and peroneal nerve. RESULTS: Higher number of NCS abnormalities was associated with higher TCNS, indicating more severe polyneuropathy. Polyneuropathy severity per the TCNS was most frequently (63%-70%) mild in patients with a low (0-1) number of NCS abnormalities, and most frequently (57%-67%) severe in patients with a high number (3-4) of NCS abnormalities, while patients with an intermediate (2) number of NCS abnormalities showed mainly mild and moderate severity with equal distribution (40%). CONCLUSIONS: A simple NCS classification system can objectively grade polyneuropathy severity, although significant overlap exists especially at the intermediate range, underscoring the importance of clinical based scoring.

Cytokines and chemokines in patients with chronic inflammatory demyelinating polyradiculoneuropathy and multifocal motor neuropathy: A systematic review.

Advances in the understanding of cytokines have revolutionized mechanistic treatments for chronic inflammatory and autoimmune diseases, as exemplified by rheumatoid arthritis. We conducted a systematic literature review on the role of cytokines and chemokines in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and multifocal motor neuropathy (MMN). Ovid Medline, EMBASE and Web of Science were searched until August 31, 2022 for human studies investigating cytokines levels in CIDP or MMN. Fifty-five articles on 1061 CIDP patients and 86 MMN patients were included, with a median of 18 patients per study (range 3-71). Studies differed in the inclusion criteria, type of assay, manufacturer, control subjects, and tested biological material. Only a minority of studies reported data on disease activity. Interleukin (IL)-6, IL-17, CXCL10, and tumor necrosis factor alpha (TNF-α), were elevated in CIDP compared to controls in most of the studies. IL-6 and TNF-α levels are also correlated with disability. In MMN patients, IL-1Ra was elevated in the majority of the reports. While acknowledging the challenges in comparing studies and the various limitations of the studies, including small patient numbers, particularly in MMN, our review suggests that IL-6, IL-17, CXCL10, and TNF-α might play a role in CIDP pathogenesis. Larger studies are needed in MMN.

[Diagnostic workup for polyneuropathy]. / Diagnostische Abklärung bei Polyneuropathie.

Polyneuropathy is a disease of the peripheral nervous system that usually results in distally emphasized, often symmetrical sensory and motor stimulation and deficits. These are often extremely painful. They can be divided into hereditary and acquired causes; inflammatory and infectious causes should be further differentiated among the acquired causes. A careful diagnostic workup is essential. Clinical signs and distribution patterns of symptoms can often already provide clues to the underlying aetiology. This review describes this workup, which in addition to the medical history and clinical examination always includes thorough laboratory diagnostics, electrophysiological examination and cerebrospinal fluid diagnostics. In individual cases, further diagnostic steps may be necessary in order to make the correct diagnosis.

A 21-bp deletion in the complement regulator CD55 promotor region is associated with multifocal motor neuropathy and its disease course.

BACKGROUND AND AIMS: To further substantiate the role of antibody-mediated complement activation in multifocal motor neuropathy (MMN) immunopathology, we investigated the distribution of promotor polymorphisms of genes encoding the membrane-bound complement regulators CD46, CD55, and CD59 in patients with MMN and controls, and evaluated their association with disease course. METHODS: We used Sanger sequencing to genotype five common polymorphisms in the promotor regions of CD46, CD55, and CD59 in 133 patients with MMN and 380 controls. We correlated each polymorphism to clinical parameters. RESULTS: The genotype frequencies of rs28371582, a 21-bp deletion in the CD55 promotor region, were altered in patients with MMN as compared to controls (p .009; Del/Del genotype 16.8% vs. 7.7%, p .005, odds ratio: 2.43 [1.27-4.58]), and patients carrying this deletion had a more favorable disease course (mean difference 0.26 Medical Research Council [MRC] points/year; 95% confidence interval [CI]: 0.040-0.490, p .019). The presence of CD59 rs141385724 was associated with less severe pre-diagnostic disease course (mean difference 0.940 MRC point/year; 95% CI: 0.083-1.80, p .032). INTERPRETATION: MMN susceptibility is associated with a 21-bp deletion in the CD55 promotor region (rs2871582), which is associated with lower CD55 expression. Patients carrying this deletion may have a more favorable long-term disease outcome. Taken together, these results point out the relevance of the pre-C5 level of the complement cascade in the inflammatory processes underlying MMN.

Patisirana no tratamento de pacientes diagnosticados com amiloidose hereditária relacionada à transtirretina (ATTRh) com polineuropatia em estágio 2 ou que apresentem resposta inadequada ao tafamidis / Patisiran in the treatment of patients diagnosed with hereditary transthyretin-related amyloidosis (hATTR) with stage 2 polyneuropathy or who have an inadequate response to tafamidis

INTRODUÇÃo: Amiloidose hereditária relacionada a transtirretina é uma doença genética rara autossômica dominante, multissistêmica, progressiva e potencialmente fatal. Após o diagnóstico deve ser determinado o estágio da doença de acordo com a gravidade dos sintomas (Estágio 0 a III), sendo o estágio III o de maior gravidade. Estima-se que a ATTRh afete cerca de 50 mil pessoas no mundo todo. No Brasil, não há dados epidemiológicos publicados sobre sua prevalência. Porém, observou-se um aumento no número de casos de ATTRh registrados no país. Atualmente, o único medicamento disponibilizado pelo SUS para tratar ATTRh é o tafamidis meglumina, indicado para pacientes adultos sintomáticos em estágio inicial (estágio I) e não submetidos a transplante hepático por ATTRh. O transplante hepático deve ser realizado apenas no estágio I da doença, em razão de não ser uma medida terapêutica curativa das lesões, que surgem nos estágios mais avançados da ATTRh. PERGUNTA: O tratamento com patisirana é eficaz, efetivo e seguro para pacientes diagnosticados com amiloidose ATTRh com polineuropatia em estágio 2 ou que apresentam resposta inadequada ao tafamidis? EVIDÊNCIAS CLÍNICAS: Os estudos selecionados demonstram a eficácia do patisirana na redução da progressão neuropática da doença, evidenciada pela diminuição da pontuação na escala mNIS+7 após uso

De novo pathogenic variant in SETX causes a rapidly progressive neurodegenerative disorder of early childhood-onset with severe axonal polyneuropathy.

Pathogenic variants in SETX cause two distinct neurological diseases, a loss-of-function recessive disorder, ataxia with oculomotor apraxia type 2 (AOA2), and a dominant gain-of-function motor neuron disorder, amyotrophic lateral sclerosis type 4 (ALS4). We identified two unrelated patients with the same de novo c.23C > T (p.Thr8Met) variant in SETX presenting with an early-onset, severe polyneuropathy. As rare private gene variation is often difficult to link to genetic neurological disease by DNA sequence alone, we used transcriptional network analysis to functionally validate these patients with severe de novo SETX-related neurodegenerative disorder. Weighted gene co-expression network analysis (WGCNA) was used to identify disease-associated modules from two different ALS4 mouse models and compared to confirmed ALS4 patient data to derive an ALS4-specific transcriptional signature. WGCNA of whole blood RNA-sequencing data from a patient with the p.Thr8Met SETX variant was compared to ALS4 and control patients to determine if this signature could be used to identify affected patients. WGCNA identified overlapping disease-associated modules in ALS4 mouse model data and ALS4 patient data. Mouse ALS4 disease-associated modules were not associated with AOA2 disease modules, confirming distinct disease-specific signatures. The expression profile of a patient carrying the c.23C > T (p.Thr8Met) variant was significantly associated with the human and mouse ALS4 signature, confirming the relationship between this SETX variant and disease. The similar clinical presentations of the two unrelated patients with the same de novo p.Thr8Met variant and the functional data provide strong evidence that the p.Thr8Met variant is pathogenic. The distinct phenotype expands the clinical spectrum of SETX-related disorders.

Association Between Severe Chronic Obstructive Pulmonary Disease and Polyneuropathy.

BACKGROUND Chronic obstructive pulmonary disease (COPD) is a life-threatening and devastating disease associated with low-grade systemic inflammation. In adults, the most common disease of the peripheral nervous system is peripheral neuropathy. While most polyneuropathy has a mixed presentation, some cases are motor dominant and others are sensory dominant. We investigated polyneuropathy in patients with COPD and hypothesized that low-grade systemic inflammation and other pathologies in patients with COPD cause peripheral axonal polyneuropathy. MATERIAL AND METHODS We included 62 patients with COPD without any neurological signs or symptoms, and 30 healthy volunteers with no known neurological or pulmonary diseases as controls. There were 38 men in the COPD group and 17 men in the control group; the mean ages of the 2 groups were 64.88 and 62.7 years, respectively. According to the Global Initiative for Chronic Obstructive Lung Disease COPD report, all COPD patients were group D. After collecting demographic and clinical characteristics of the participants, we performed an electrophysiological examination to investigate polyneuropathy and pulmonary function test results. C-reactive protein, hemoglobin, creatinine, partial carbon dioxide pressure (pCO2) levels were recorded. Electrophysiological examination was performed with a Medelec Synergy device using standard neurographic procedures, and the results were assessed. RESULTS Significant differences were found for forced expiratory volume in 1 sec (FEV1), %FEV1, forced vital capacity (FVC), %FVC, pCO2, and hemoglobin and creatinine levels, but all participants had a creatinine level within the normal range. There was no difference in sensory neuropathy between the groups, but a significant difference was found in terms of motor neuropathy. CONCLUSIONS As noted in previous studies, systemic inflammation, increased oxidative stress, decreased oxygen pressure, and multiple comorbidities in patients with COPD may all contribute to the development of neuropathy.

The Phenotypic Spectrum of Patients with PHARC Syndrome Due to Variants in ABHD12: An Ophthalmic Perspective.

This study investigated the phenotypic spectrum of PHARC (polyneuropathy, hearing loss, ataxia, retinitis pigmentosa and early-onset cataract) syndrome caused by biallelic variants in the ABHD12 gene. A total of 15 patients from 12 different families were included, with a mean age of 36.7 years (standard deviation [SD] ± 11.0; range from 17.5 to 53.9) at the most recent examination. The presence and onset of neurological, audiological and ophthalmic symptoms were variable, with no evident order of symptom appearance. The mean best-corrected visual acuity was 1.1 logMAR (SD ± 0.9; range from 0.1 to 2.8; equivalent to 20/250 Snellen) and showed a trend of progressive decline. Different types of cataract were observed in 13 out of 15 patients (87%), which also included congenital forms of cataract. Fundus examination revealed macular involvement in all patients, ranging from alterations of the retinal pigment epithelium to macular atrophy. Intraretinal spicular hyperpigmentation was observed in 7 out of 15 patients (47%). From an ophthalmic perspective, clinical manifestations in patients with PHARC demonstrate variability with regard to their onset and severity. Given the variable nature of PHARC, an early multidisciplinary assessment is recommended to assess disease severity.

Anticipation and compensation for somatosensory deficits in object handling: evidence from a patient with large fiber sensory neuropathy.

The purpose of this study was to determine the contributions of feedforward and feedback processes on grip force regulation and object orientation during functional manipulation tasks. One patient with massive somatosensory loss resulting from large fiber sensory neuropathy and 10 control participants were recruited. Three experiments were conducted: 1) perturbation to static holding; 2) discrete vertical movement; and 3) functional grasp and place. The availability of visual feedback was also manipulated to assess the nature of compensatory mechanisms. Results from experiment 1 indicated that both the deafferented patient and controls used anticipatory grip force adjustments before self-induced perturbation to static holding. The patient exhibited increased grip response time, but the magnitude of grip force adjustments remained correlated with perturbation forces in the self-induced and external perturbation conditions. In experiment 2, the patient applied peak grip force substantially in advance of maximum load force. Unlike controls, the patient's ability to regulate object orientation was impaired without visual feedback. In experiment 3, the duration of unloading, transport, and release phases were longer for the patient, with increased deviation of object orientation at phase transitions. These findings show that the deafferented patient uses distinct modes of anticipatory control according to task constraints and that responses to perturbations are mediated by alternative afferent information. The loss of somatosensory feedback thus appears to impair control of object orientation, whereas variation in the temporal organization of functional tasks may reflect strategies to mitigate object instability associated with changes in movement dynamics.NEW & NOTEWORTHY This study evaluates the effects of sensory neuropathy on the scaling and timing of grip force adjustments across different object handling tasks (i.e., holding, vertical movement, grasping, and placement). In particular, these results illustrate how novel anticipatory and online control processes emerge to compensate for the loss of somatosensory feedback. In addition, we provide new evidence on the role of somatosensory feedback for regulating object orientation during functional prehensile movement.

Adducted Thumb and Peripheral Polyneuropathy: Diagnostic Supports in Suspecting White-Sutton Syndrome: Case Report and Review of the Literature.

One of the recently described syndromes emerging from the massive study of cohorts of undiagnosed patients with autism spectrum disorders (ASD) and syndromic intellectual disability (ID) is White-Sutton syndrome (WHSUS) (MIM #616364), caused by variants in the POGZ gene (MIM *614787), located on the long arm of chromosome 1 (1q21.3). So far, more than 50 individuals have been reported worldwide, although phenotypic features and natural history have not been exhaustively characterized yet. The phenotypic spectrum of the WHSUS is broad and includes moderate to severe ID, microcephaly, variable cerebral malformations, short stature, brachydactyly, visual abnormalities, sensorineural hearing loss, hypotonia, sleep difficulties, autistic features, self-injurious behaviour, feeding difficulties, gastroesophageal reflux, and other less frequent features. Here, we report the case of a girl with microcephaly, brain malformations, developmental delay (DD), peripheral polyneuropathy, and adducted thumb-a remarkable clinical feature in the first years of life-and heterozygous for a previously unreported, de novo splicing variant in POGZ. This report contributes to strengthen and expand the knowledge of the clinical spectrum of WHSUS, pointing out the importance of less frequent clinical signs as diagnostic handles in suspecting this condition.

Electrodiagnostic findings in patients with non-COVID-19- and COVID-19-related acute respiratory distress syndrome.

BACKGROUND: Critical illness polyneuropathy and myopathy (CIPNM) is a frequent neurological manifestation in patients with acute respiratory distress syndrome (ARDS) from coronavirus disease 2019 (COVID-19) infection. CIPNM diagnosis is usually limited to clinical evaluation. We compared patients with ARDS from COVID-19 and other aetiologies, in whom a neurophysiological evaluation for the detection of CIPNM was performed. The aim was to determine if there were any differences between these two groups in frequency of CINPM and outcome at discharge from the intensive care unit (ICU). MATERIALS AND METHODS: This was a single-centre retrospective study performed on mechanically ventilated patients consecutively admitted (January 2016-June 2020) to the ICU of Careggi Hospital, Florence, Italy, with ARDS of different aetiologies. Neurophysiological evaluation was performed on patients with stable ventilation parameters, but marked widespread hyposthenia (Medical Research Council score <48). Creatine phosphokinase (CPK), lactic dehydrogenase (LDH) and mean morning glycaemic values were collected. RESULTS: From a total of 148 patients, 23 with COVID-19 infection and 21 with ARDS due to other aetiologies, underwent electroneurography/electromyography (ENG/EMG) recording. Incidence of CIPNM was similar in the two groups, 65% (15 of 23) in COVID-19 patients and 71% (15 of 21) in patients affected by ARDS of other aetiologies. At ICU discharge, subjects with CIPNM more frequently required ventilatory support, regardless the aetiology of ARDS. CONCLUSION: ENG/EMG represents a useful tool in the identification of the neuromuscular causes underlying ventilator wean failure and patient stratification. A high incidence of CIPNM, with a similar percentage, has been observed in ARDS patients of all aetiologies.

Berg balance scale as a tool for choosing the walking aid for patients with Guillain-Barré syndrome or polyneuropathy.

Berg balance scale (BBS) is a widely used outcome measure in rehabilitation. We wanted to check if it can discriminate among levels of use of walking aid in patients with Guillain-Barré syndrome or polyneuropathy. A retrospective audit of 109 such patients (aged 16-85 years) who had completed inpatient rehabilitation in the period 2012-2017 was conducted. Receiver operating characteristic curve analysis was used to estimate the thresholds that optimise the prediction of the patient's walking aid. Statistically, significant threshold BBS score was estimated for the ability to walk without walking aid (≥49 points, yielding 88% sensitivity, 68% specificity and 83% classification accuracy) and the necessity to walk with a walker (≤37 points, yielding 62% sensitivity, 83% specificity and 78% classification accuracy). BBS score thresholds can therefore help clinicians choose the appropriate walking aid for patients with Guillain-Barré syndrome or polyneuropathy undergoing rehabilitation.

Critical illness polyneuropathy, myopathy and neuronal biomarkers in COVID-19 patients: A prospective study.

OBJECTIVE: The aim was to characterize the electrophysiological features and plasma biomarkers of critical illness polyneuropathy (CIN) and myopathy (CIM) in coronavirus disease 2019 (COVID-19) patients with intensive care unit acquired weakness (ICUAW). METHODS: An observational ICU cohort study including adult patients admitted to the ICU at Uppsala University Hospital, Uppsala, Sweden, from March 13th to June 8th 2020. We compared the clinical, electrophysiological and plasma biomarker data between COVID-19 patients who developed CIN/CIM and those who did not. Electrophysiological characteristics were also compared between COVID-19 and non-COVID-19 ICU patients. RESULTS: 111 COVID-19 patients were included, 11 of whom developed CIN/CIM. Patients with CIN/CIM had more severe illness; longer ICU stay, more thromboembolic events and were more frequently treated with invasive ventilation for longer than 2 weeks. In particular CIN was more frequent among COVID-19 patients with ICUAW (50%) compared with a non-COVID-19 cohort (0%, p = 0.008). Neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAp) levels were higher in the CIN/CIM group compared with those that did not develop CIN/CIM (both p = 0.001) and correlated with nerve amplitudes. CONCLUSIONS: CIN/CIM was more prevalent among COVID-19 ICU patients with severe illness. SIGNIFICANCE: COVID-19 patients who later developed CIN/CIM had significantly higher NfL and GFAp in the early phase of ICU care, suggesting their potential as predictive biomarkers for CIN/CIM.

Saphenous nerve to posterior tibial nerve transfer: A new approach to restore sensations of sole in diabetic sensory polyneuropathy.

BACKGROUND: Loss of sensations in the sole following diabetic sensorimotor polyneuropathy (DSPN) leads to diabetic foot ulcers and its sequelae. We hypothesized that sensory reinnervation of sole by transfer of saphenous nerve (SN) to sensory fascicles of posterior tibial nerve (PTN) in these patients may reverse the neuropathy. METHODS: This prospective interventional case series included patients with advanced DSPN and intact sensory supply of SN. PTN was neurotized by transfer of SN nerve in the tarsal tunnel and postoperatively sensations of the sole were tested. Any existing ulcers on sole were noted and their healing was monitored. FINDING: A total of 17 patients (22 feet), 9 male and 8 female, were included. Seven patients had ulcers in the feet. At 6 months follow-up all patients developed protective sensation in the sole. The average 2 PD improved from 60 mm to 45.5 mm, average vibration perception improved from 34.12 V to 24.33, Medical Research Council (MRC) score improved from S0 in 12 feet and S1 in 10 feet to S3+ in 13 feet, S3 in 5 feet, and S2 in 2 feet at 6 months along with healing of ulcers in all 7 feet. INTERPRETATION: Transfer of SN to PTN for sensory neurotization is an innovative and simple option to prevent complications of DSPN. This procedure has the potential to change the natural history of DSPN.

Clinical features with anti fibroblast growth factor receptor 3 (FGFR3) antibody-related polyneuropathy: a retrospective study.

BACKGROUND: Despite its initial association with sensory neuropathies, anti-fibroblast growth factor receptor 3 (FGFR3) antibodies have been since reported with a broad range of neuropathies and clinical features. The aim of the study is to report the clinical and electro diagnostic findings in a cohort of patients with sensory or sensorimotor polyneuropathy and anti-FGFR3 antibodies. METHODS: We performed a retrospective chart review to assess the clinical characteristics of patients with sensory or sensorimotor neuropathy related to FGFR3 antibodies. Descriptive statistics were reported using frequencies and percentages for categorical variables and median and interquartile range (IQR) for continuous variables. RESULTS: This study included 14 patients (9 women) with a median age of 51.9 years (IQR 48-57). The most common presenting symptoms were painful paresthesia (100%), gait instability (42.9%), constitutional symptoms (42.9%), and autonomic symptoms (28.6%). Onset of symptoms was chronic (≥12 weeks) in eight patients (57.1%). Examination showed a distal loss of sensation to pin prick (100%), as well as impaired vibration sensation (78.6%) and proprioception (35.7%), in the distal extremities. We also observed mild weakness in the distal lower-extremities (42.9%). Three patients (21.4%) had trigeminal neuralgia, three patients (21.4%) had co-existing autoimmune disease, and one patient (7.1%) had a history of renal cell carcinoma. The mean titer of FGFR3 antibody was 14,285.71 (IQR 5000-16,750). All 14 patients produced normal results in the neuropathy workup. Nerve conduction study and electromyography showed sensory axonal neuropathy in four patients (28.6%), sensorimotor axonal neuropathy in seven patients (50%), and a normal result in three patients (21.4%). For those with a normal NCS/EMG, a skin biopsy showed a non-length-dependent small fiber neuropathy. CONCLUSIONS: Neuropathy related to FGFR3 antibodies can potentially involve small and large fibers, sensory and motor fibers, and even the trigeminal nerve, which contributes to a highly variable clinical presentation.

Pattern of muscle strength improvement after intravenous immunoglobulin therapy in multifocal motor neuropathy.

INTRODUCTION: In multifocal motor neuropathy (MMN), knowledge about the pattern of treatment response in a wide spectrum of muscle groups, distal as well as proximal, after intravenous immunoglobulin (IVIg) initiation is lacking. METHODS: Hand-held dynamometry data of 11 upper and lower limb muscles, from 47 patients with MMN was reviewed. Linear mixed models were used to determine the treatment response after IVIg initiation and its relationship with initial muscle weakness. RESULTS: All muscle groups showed a positive treatment response after IVIg initiation. Changes in SD scores ranged from +0.1 to +0.95. A strong association between weakness at baseline and the magnitude of the treatment response was found. DISCUSSION: Improved muscle strength in response to IVIg appears not only in distal, but to a similar degree also in proximal muscle groups in MMN, with the largest response in muscle groups that show the greatest initial weakness.