The unfolded protein response in amyotrophic later sclerosis: results of a phase 2 trial.

Strong evidence suggests that endoplasmic reticulum stress plays a critical role in the pathogenesis of amyotrophic lateral sclerosis (ALS) through altered regulation of proteostasis. Robust preclinical findings demonstrated that guanabenz selectively inhibits endoplasmic reticulum stress-induced eIF2α-phosphatase, allowing misfolded protein clearance, reduces neuronal death and prolongs survival in in vitro and in vivo models. However, its safety and efficacy in patients with ALS are unknown. To address these issues, we conducted a multicentre, randomized, double-blind trial with a futility design. Patients with ALS who had displayed an onset of symptoms within the previous 18 months were randomly assigned in a 1:1:1:1 ratio to receive 64 mg, 32 mg or 16 mg of guanabenz or placebo daily for 6 months as an add-on therapy to riluzole. The purpose of the placebo group blinding was to determine safety but not efficacy. The primary outcome was the proportion of patients progressing to higher stages of disease within 6 months as measured using the ALS Milano-Torino staging system, compared with a historical cohort of 200 patients with ALS. The secondary outcomes were the rate of decline in the total revised ALS functional rating scale score, slow vital capacity change, time to death, tracheotomy or permanent ventilation and serum light neurofilament level at 6 months. The primary assessment of efficacy was performed using intention-to-treat analysis. The treatment arms using 64 mg and 32 mg guanabenz, both alone and combined, reached the primary hypothesis of non-futility, with the proportions of patients who progressed to higher stages of disease at 6 months being significantly lower than that expected under the hypothesis of non-futility and a significantly lower difference in the median rate of change in the total revised ALS functional rating scale score. This effect was driven by patients with bulbar onset, none of whom (0/18) progressed to a higher stage of disease at 6 months compared with those on 16 mg guanabenz (4/8; 50%), the historical cohort alone (21/49; 43%; P = 0.001) or plus placebo (25/60; 42%; P = 0.001). The proportion of patients who experienced at least one adverse event was higher in any guanabenz arm than in the placebo arm, with higher dosing arms having a significantly higher proportion of drug-related side effects and the 64 mg arm a significantly higher drop-out rate. The number of serious adverse events did not significantly differ between the guanabenz arms and the placebo. Our findings indicate that a larger trial with a molecule targeting the unfolded protein response pathway without the alpha-2 adrenergic related side-effect profile of guanabenz is warranted.

Validation of the DYALS (dysphagia in amyotrophic lateral sclerosis) questionnaire for the evaluation of dysphagia in ALS patients.

BACKGROUND: Dysphagia is a common symptom during the trajectory of ALS, and it can significantly impact on the quality of life and prognosis of patients. Nowadays, no specific tool for the screening of dysphagia in ALS is validated, and the approach is heterogeneous across the Italian centres. OBJECTIVE: To validate the DYALS (dysphagia in amyotrophic lateral sclerosis) questionnaire, adapting the DYMUS (dysphagia in multiple sclerosis) questionnaire, for the assessment of dysphagia in ALS patients, in order to uniform the evaluations across the Italian ALS network. METHODS: We included 197 patients diagnosed with ALS following the El Escorial criteria, in sixteen Italian ALS centres between 1st December 2019 and 1st July 2020. For each patient, we collected clinical and demographic data and obtained ALSFRS-r score, ALSAQ-5 score, DYMUS score, and EAT-10 score. RESULTS: Across the 197 patients, the ratio M/F was 113/84, and the median age was 64 years (IQR 56-72.5). Bulbar patients were 20%, and spinal patients 80%. The median ALSFRSr total score of patients was 35 (IQR 28-39). DYALS score was statistically higher in bulbar ALS than in spinal ALS (median = 6, IQR 4.5-9 vs median = 1, IQR 0-5, z = 6.253, p < 0.0001). DYALS questionnaire showed a high internal consistency (Cronbach's alpha = 0.88). There was a statistically significant correlation between DYALS and EAT-10 (rho = 0.90, p < 0.0001). CONCLUSIONS: DYALS scale is reliable, manageable, and easily usable for the screening of dysphagia in ALS. It can be shared with all the Italian ALS centres in order to collect uniform data for therapeutic strategies and clinical trials.

Erythropoietin in amyotrophic lateral sclerosis: a multicentre, randomised, double blind, placebo controlled, phase III study.

OBJECTIVE: To assess the efficacy of recombinant human erythropoietin (rhEPO) in amyotrophic lateral sclerosis (ALS). METHODS: Patients with probable laboratory-supported, probable or definite ALS were enrolled by 25 Italian centres and randomly assigned (1:1) to receive intravenous rhEPO 40,000 IU or placebo fortnightly as add-on treatment to riluzole 100 mg daily for 12 months. The primary composite outcome was survival, tracheotomy or >23 h non-invasive ventilation (NIV). Secondary outcomes were ALSFRS-R, slow vital capacity (sVC) and quality of life (ALSAQ-40) decline. Tolerability was evaluated analysing adverse events (AEs) causing withdrawal. The randomisation sequence was computer-generated by blocks, stratified by centre, disease severity (ALSFRS-R cut-off score of 33) and onset (spinal or bulbar). The main outcome analysis was performed in all randomised patients and by intention-to-treat for the entire population and patients stratified by severity and onset. The study is registered, EudraCT 2009-016066-91. RESULTS: We randomly assigned 208 patients, of whom 5 (1 rhEPO and 4 placebo) withdrew consent and 3 (placebo) became ineligible (retinal thrombosis, respiratory insufficiency, SOD1 mutation) before receiving treatment; 103 receiving rhEPO and 97 placebo were eligible for analysis. At 12 months, the annualised rate of death (rhEPO 0.11, 95% CI 0.06 to 0.20; placebo: 0.08, CI 0.04 to 0.17), tracheotomy or >23 h NIV (rhEPO 0.16, CI 0.10 to 0.27; placebo 0.18, CI 0.11 to 0.30) did not differ between groups, also after stratification by onset and ALSFRS-R at baseline. Withdrawal due to AE was 16.5% in rhEPO and 8.3% in placebo. No differences were found for secondary outcomes. CONCLUSIONS: RhEPO 40,000 IU fortnightly did not change the course of ALS.

Natura non facit saltus in anti-ganglioside antibody-mediated neuropathies.

Natura non facit saltus (Latin for "nature does not make jumps") is a maxim expressing the idea that natural things and properties change gradually, in a continuum, rather than suddenly. In biomedical sciences, for taxonomic purposes, we make jumps that emphasize differences more than similarities. Among the dysimmune neuropathies, 2 disorders, characterized by the presence of antibodies to gangliosides GM1 and GD1a and a peculiar, exclusive motor involvement, have been identified: acute motor axonal neuropathy (AMAN) and multifocal motor neuropathy (MMN). However, anti-GM1 or -GD1a antibodies are also associated with acute motor and sensory axonal motor neuropathy (AMSAN). We review the results of recent clinical and experimental studies showing that AMAN and MMN are not exclusively motor. We discuss the possible explanations for the greater resistance of sensory fibers to antibody attack to finally suggest that AMAN, AMSAN, and MMN belong to a continuous spectrum with a common pathophysiological mechanism.

Involvement of sensory fibres in axonal subtypes of Guillain-Barre syndrome.

BACKGROUND: Acute motor axonal neuropathy (AMAN) and acute motor and sensory axonal neuropathy (AMSAN) are due to an antiganglioside antibody mediated attack, thought to be restricted to motor fibres in AMAN. Sensory symptoms and minor sensory conduction abnormalities, however, have been reported in some AMAN patients. OBJECTIVE: To verify whether sensory fibres are truly spared in AMAN and whether AMAN and AMSAN represent a continuum. METHODS: Serial conduction studies in 13 AMAN and three AMSAN patients were reviewed. To evaluate the variation in sensory nerve action potential (SNAP) amplitude in serial recordings, the least significant change in a test-retest study of 20 controls was calculated. Least significant change for median, ulnar and sural nerves were 44%, 47% and 58%, respectively. RESULTS: In 34% of initially normal sensory nerves of six AMAN patients, SNAP amplitude significantly increased by 57-518%. In three nerves of three AMAN patients, SNAP significantly decreased by 50-69%. Overall, serial recordings allowed detection of sensory fibre involvement in 49% of nerves and in 69% of AMAN patients. In one AMSAN patient, SNAP increased in two nerves by 150-300%; in another patient, SNAPs, unrecordable at baseline in six nerves, reappeared during follow-up and normalised in three nerves. In five nerves of three AMAN and in eight nerves of two AMSAN patients, SNAP amplitudes increased rapidly, suggesting reversible conduction failure of sensory fibres. In other nerves, SNAP increased over months, as for axonal regeneration. CONCLUSIONS: Sensory fibres are often involved subclinically in AMAN. Reversible conduction failure may develop in sensory as well as motor fibres in both AMAN and AMSAN. AMAN and AMSAN represent a continuum in axonal GBS.

Diabetes Mellitus and Amyotrophic Lateral Sclerosis: A Systematic Review.

BACKGROUND: Amyotrophic Lateral Sclerosis (ALS) is a degenerative disorder which affects the motor neurons. Growing evidence suggests that ALS may impact the metabolic system, including the glucose metabolism. Several studies investigated the role of Diabetes Mellitus (DM) as risk and/or prognostic factor. However, a clear correlation between DM and ALS has not been defined. In this review, we focus on the role of DM in ALS, examining the different hypotheses on how perturbations of glucose metabolism may interact with the pathophysiology and the course of ALS. METHODS: We undertook an independent PubMed literature search, using the following search terms: ((ALS) OR (Amyotrophic Lateral Sclerosis) OR (Motor Neuron Disease)) AND ((Diabetes) OR (Glucose Intolerance) OR (Hyperglycemia)). Review and original articles were considered. RESULTS: DM appears not to affect ALS severity, progression, and survival. Contrasting data suggested a protective role of DM on the occurrence of ALS in elderly and an opposite effect in younger subjects. CONCLUSIONS: The actual clinical and pathophysiological correlation between DM and ALS is unclear. Large longitudinal prospective studies are needed. Achieving large sample sizes comparable to those of common complex diseases like DM is a challenge for a rare disease like ALS. Collaborative efforts could overcome this specific issue.

Pitfalls in electrodiagnosis of Guillain-Barré syndrome subtypes.

OBJECTIVE: To electrophysiologically classify an Italian Guillain-Barré syndrome (GBS) population into demyelinating and axonal subtypes, to investigate how serial recordings changed the classification and to underline the pitfalls in electrodiagnosis of GBS subtypes. METHODS: The authors applied two current electrodiagnostic criteria sets for demyelinating and axonal GBS subtypes in 55 patients who had at least two serial recordings in three motor and sensory nerves. RESULTS: At first test, the electrodiagnosis was almost identical with both criteria: 65-67% of patients were classifiable as acute inflammatory demyelinating polyradiculoneuropathy (AIDP), 18% were classifiable as axonal GBS, and 14-16% were equivocal. At follow-up, 24% of patients changed classification: AIDP decreased to 58%, axonal GBS increased to 38%, and equivocal patients decreased to 4%. The majority of shifts were from AIDP and equivocal groups to axonal GBS, and the main reason was the recognition by serial recordings of the reversible conduction failure and of the length-dependent compound muscle action potential amplitude reduction patterns as expression of axonal pathology. CONCLUSIONS: Axonal GBS is pathophysiologically characterised not only by axonal degeneration but also by reversible conduction failure at the axolemma of the Ranvier node. The lack of distinction among demyelinating conduction block, reversible conduction failure and length-dependent compound muscle action potential amplitude reduction may fallaciously classify patients with axonal GBS as having AIDP. Serial electrophysiological studies are mandatory for proper diagnosis of GBS subtypes and the identification of pathophysiological mechanisms of muscle weakness. More reliable electrodiagnostic criteria taking into consideration the reversible conduction failure pattern should be devised.

Reversible conduction failure in pharyngeal-cervical-brachial variant of Guillain-Barré syndrome.

In two patients with the pharyngeal-cervical-brachial variant (PCB) of Guillain-Barré syndrome (GBS), low amplitude distal compound muscle action potentials and partial motor conduction blocks normalized without development of excessive temporal dispersion within 4 weeks. Sensory nerve action potentials significantly improved in amplitude or, when absent, rapidly became recordable at follow-up. Besides axonal degeneration, PCB is characterized by reversible conduction failure in both motor and sensory fibers and is in the continuous spectrum of axonal GBS subtypes.

Genome-wide Analyses Identify KIF5A as a Novel ALS Gene.

To identify novel genes associated with ALS, we undertook two lines of investigation. We carried out a genome-wide association study comparing 20,806 ALS cases and 59,804 controls. Independently, we performed a rare variant burden analysis comparing 1,138 index familial ALS cases and 19,494 controls. Through both approaches, we identified kinesin family member 5A (KIF5A) as a novel gene associated with ALS. Interestingly, mutations predominantly in the N-terminal motor domain of KIF5A are causative for two neurodegenerative diseases: hereditary spastic paraplegia (SPG10) and Charcot-Marie-Tooth type 2 (CMT2). In contrast, ALS-associated mutations are primarily located at the C-terminal cargo-binding tail domain and patients harboring loss-of-function mutations displayed an extended survival relative to typical ALS cases. Taken together, these results broaden the phenotype spectrum resulting from mutations in KIF5A and strengthen the role of cytoskeletal defects in the pathogenesis of ALS.

Antioxidant strategies based on tomato-enriched food or pyruvate do not affect disease onset and survival in an animal model of amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder which is mostly sporadic, although about 5-10% of the cases are inherited. About 15-20% of patients with familial ALS (FALS) carry mutations in the gene encoding the free radical scavenging enzyme Cu/Zn superoxide dismutase (SOD1). In this study, we explored the potential neuroprotective effects of antioxidant strategies based on either a tomato-enriched diet, or pyruvate administration, in an animal model of ALS. To that aim, transgenic mice expressing a mutant form of SOD1 [the gly(93) --> ala (G93A) substitution; G93A SOD1] were fed on either tomato-enriched food pellets or the Altromin diet in which milk serum and proteins substitute for soy and fish flours. In both cases, treatments were started at the 29th day of age. In a second set of experiments, G93A SOD1 mice were treated with pyruvate intraperitoneally (500 mg/kg, i.p; starting at the 70th day of age) and compared with control mice receiving i.p. saline injections. Our results indicate that neither the tomato-enriched diet nor pyruvate administration caused any significant effect on the overall survival time and disease onset in G93A SOD1 mice. Thus, despite the wealth of data indicating the relevant role of oxidative stress and defective energy homeostasis both in patients and animal models of ALS, antioxidant strategies based on tomato-enriched food or pyruvate seem to be not sufficient to promote a disease modifying effect in an animal model of ALS.

Epilepsy and electroencephalographic abnormalities in C9orf72 repeat expansion.

A patient has been recently described with frontotemporal cognitive decline and C9orf72 repeat expansion who presented abnormally slowed background and photoparoxysmal response at electroencephalographic (EEG) recording. Our data, based on five patients with repeat expansions in C9orf72 and EEG recordings suggest that abnormally slowed background and epilepsy represent previously unrecognized features of the C9orf72 phenotype in some patients.

Protein misfolding, amyotrophic lateral sclerosis and guanabenz: protocol for a phase II RCT with futility design (ProMISe trial).

INTRODUCTION: Recent studies suggest that endoplasmic reticulum stress may play a critical role in the pathogenesis of amyotrophic lateral sclerosis (ALS) through an altered regulation of the proteostasis, the cellular pathway-balancing protein synthesis and degradation. A key mechanism is thought to be the dephosphorylation of eIF2α, a factor involved in the initiation of protein translation. Guanabenz is an alpha-2-adrenergic receptor agonist safely used in past to treat mild hypertension and is now an orphan drug. A pharmacological action recently discovered is its ability to modulate the synthesis of proteins by the activation of translational factors preventing misfolded protein accumulation and endoplasmic reticulum overload. Guanabenz proved to rescue motoneurons from misfolding protein stress both in in vitro and in vivo ALS models, making it a potential disease-modifying drug in patients. It is conceivable investigating whether its neuroprotective effects based on the inhibition of eIF2α dephosphorylation can change the progression of ALS. METHODS AND ANALYSES: Protocolised Management In Sepsis is a multicentre, randomised, double-blind, placebo-controlled phase II clinical trial with futility design. We will investigate clinical outcomes, safety, tolerability and biomarkers of neurodegeneration in patients with ALS treated with guanabenz or riluzole alone for 6 months. The primary aim is to test if guanabenz can reduce the proportion of patients progressed to a higher stage of disease at 6 months compared with their baseline stage as measured by the ALS Milano-Torino Staging (ALS-MITOS) system and to the placebo group. Secondary aims are safety, tolerability and change in at least one biomarker of neurodegeneration in the guanabenz arm compared with the placebo group. Findings will provide reliable data on the likelihood that guanabenz can slow the course of ALS in a phase III trial. ETHICS AND DISSEMINATION: The study protocol was approved by the Ethics Committee of IRCCS 'Carlo Besta Foundation' of Milan (Eudract no. 2014-005367-32 Pre-results) based on the Helsinki declaration.

Experimental axonopathy induced by immunization with Campylobacter jejuni lipopolysaccharide from a patient with Guillain-Barré syndrome.

New Zealand white rabbits were immunized with a lipopolysaccharide (LPS) extracted from a Campylobacter jejuni HS:19 strain isolated from a GBS patient expressing GM1 and GD1a-like epitopes, Freund's adjuvant (group I) and Freund's adjuvant plus keyhole lympet hemocyanin (KLH) (group II). Both groups showed high titers of anti-LPS and anti-GM1 and lower titers of anti-GD1b and anti-GD1a antibodies. Weakness and axonal degeneration in sciatic nerves was detected in 1/11 of group I and 6/7 of group II. This model replicates, at least in part, the pathogenetic process hypothesized in the human axonal GBS with antiganglioside antibodies post C. jejuni infection and indicates that KLH plays an additional role in neuropathy induction.

Olanzapine-related repetitive focal seizures with lingual dystonia.

Olanzapine-related seizures have rarely been reported despite associated proconvulsant risk factors described in the literature: myoclonic status, increased frequency of seizures, tonic-clonic seizures, as well as fatal status epilepticus. We present a psychiatric patient who developed repetitive focal motor seizures and lingual dystonia when olanzapine was added for psychomotor agitation and aggressiveness. Olanzapine was immediately suspended and the seizures progressively disappeared. A control EEG showed no paroxysmal discharges. Olanzapine shares some pharmacological similarities with clozapine, a neuroleptic with a high risk of dose-dependent seizures. This adverse effect should be taken into account, and olanzapine should be used with caution if concomitant circumstances decrease the seizure threshold. [Published with video sequence online].

ATNX2 is not a regulatory gene in Italian amyotrophic lateral sclerosis patients with C9ORF72 GGGGCC expansion.

There are indications that both familial amyotrophic lateral sclerosis (ALS) and sporadic ALS phenotype and prognosis are partly regulated by genetic and environmental factors, supporting the theory that ALS is a multifactorial disease. The aim of this article was to assess the role of ATXN2 intermediate length repeats in a large series of Italian and Sardinian ALS patients and controls carrying a pathogenetic C9ORF72 GGGGCC hexanucleotide repeat. A total of 1972 ALS cases were identified through the database of the Italian ALS Genetic consortium, a collaborative effort including 18 ALS centers throughout Italy. The study population included: (1) 276 Italian and 57 Sardinian ALS cases who carried the C9ORF72 expansion; (2) 1340 Italian and 299 Sardinian ALS cases not carrying the C9ORF72 expansion. A total of healthy 1043 controls were also assessed. Most Italian and Sardinian cases and controls were homozygous for 22/22 or 23/23 repeats or heterozygous for 22/23 repeats of the ATXN2 gene. ATXN2 intermediate length repeats alleles (≥28) were detected in 3 (0.6%) Italian ALS cases carrying the C9ORF72 expansion, in none of the Sardinian ALS cases carrying the expansion, in 60 (4.3%) Italian cases not carrying the expansion, and in 6 (2.0%) Sardinian ALS cases without C9ORF72 expansion. Intermediate length repeat alleles were found in 12 (1.5%) Italian controls and 1 (0.84%) Sardinian controls. Therefore, ALS patients with C9ORF72 expansion showed a lower frequency of ATXN2 polyQ intermediate length repeats than both controls (Italian cases, p = 0.137; Sardinian cases, p = 0.0001) and ALS patients without C9ORF72 expansion (Italian cases, p = 0.005; Sardinian cases, p = 0.178). In our large study on Italian and Sardinian ALS patients with C9ORF72 GGGGCC hexanucleotide repeat expansion, compared to age-, gender- and ethnic-matched controls, ATXN2 polyQ intermediate length does not represent a modifier of ALS risk, differently from non-C9ORF72 mutated patients.

Zinc dyshomeostasis: a key modulator of neuronal injury.

Zn2+ is a potently toxic cation involved in the neuronal injury observed in cerebral ischemia, epilepsy, and brain trauma. Toxic Zn2+ accumulation may result from either trans-synaptic Zn2+movement and/or cation mobilization from intracellular sites. To gain entry to the cytosol, Zn2+ can flux through glutamate receptor-associated channels, voltage-sensitive calcium channels, or Zn2+-sensitive membrane transporters, while metallothioneins and mitochondria provide sites of intracellular Zn2+ release. Intracellular Zn2+ homeostasis is sensitive to patho-physiological environmental changes, such as acidosis, inflammation and oxidative stress. The mechanisms by which Zn2+ exerts its neurotoxicity include mitochondrial and extra-mitochondrial production of reactive oxygen species and disruption of metabolic enzymatic activity, ultimately leading to activation of apoptotic and/or necrotic processes. Beside acute neuronal injury, an exciting new area of investigation is offered by the role of Zn2+ dysmetabolism in Alzheimer's disease as the cation acts as a potent trigger for Abeta aggregation and plaque formation. Finally, recent findings suggest that alteration of Zn2+ homeostasis might also be a critical contributor to aging-related neurodegenerative processes. Thus, multiple evidence suggest that modulation of intracellular and extracellular Zn2+ might be an important therapeutical target for the treatment of a vast array of neurological conditions ranging from stroke to Alzheimer's disease.

Critical Illness Neuromyopathy Complicating Akinetic Crisis in Parkinsonism: Report of 3 Cases.

Akinetic crisis (AC) is a life-threatening complication of parkinsonism characterized by an acute severe akinetic-hypertonic state, consciousness disturbance, hyperthermia, and muscle enzymes elevation. Injectable dopaminomimetic drugs, high-dose methylprednisolone, and dantrolene are advocated as putative specific treatments. The course of the illness is frequently complicated by infections, pulmonary embolism, renal failure, disseminated intravascular coagulation, and cardiac arrhythmias. Critical illness neuromyopathy (CINM) is an acquired neuromuscular disorder characterized by flaccid quadriparesis and muscle enzyme elevation, often occurring in intensive care units and primarily associated with inactivity, sepsis, multiorgan failure, neuromuscular blocking agents, and steroid treatment. In 3 parkinsonian patients, during the course of AC we observed disappearance of rigidity but persistent hypoactivity. In all, neurological examination showed quadriparesis with loss of tendon reflexes and laboratory investigation disclosed a second peak of muscle enzymes elevation, following the first increment due to AC. Electrophysiological studies showed absent or reduced sensory nerve action potentials and compound muscular action potentials, myopathic changes, and fibrillation potentials at electromyography recordings, and reduced excitability or inexcitability of tibialis anterior at direct muscle stimulation, leading to a diagnosis of CINM in all 3 patients. In 1 patient, the diagnosis was also confirmed by muscle biopsy. Outcome was fatal in 2 of the 3 patients. Although AC is associated with most of the known risk factors for CINM, the cooccurrence of the 2 disorders may be difficult to recognize and has never been reported. We found that CINM can occur as a severe complication of AC, and should be suspected when hypertonia-rigidity subsides despite persistent akinesia. Strict monitoring of muscle enzyme levels may help diagnosis. This finding addresses possible caveats in the use of putative treatments for AC.

Can electrophysiology differentiate polyneuropathy with anti-MAG/SGPG antibodies from chronic inflammatory demyelinating polyneuropathy?

OBJECTIVES: Patients with polyneuropathy and antibodies to myelin-associated glycoprotein (MAG) and sulphated glucuronyl paragloboside (SGPG) differ from chronic inflammatory demyelinating polyneuropathy (CIDP) because of a slower, progressive course, symmetrical and predominantly sensory involvement of legs, predominantly distal slowing of motor conductions, and poorer response to therapy. We studied whether a wide set of electrophysiologic parameters may differentiate these two neuropathies. METHODS: We reviewed the electrophysiological studies of 10 patients with anti-MAG/SGPG antibodies and 22 with CIDP examining: (1) motor conduction velocity and distal compound muscle action potential amplitude; (2) conduction block (CB) and temporal dispersion; (3) distal motor latency and terminal latency index (TLI); (4) F wave and proximal conduction time; and (5) sensory conduction and occurrence of abnormal median with normal sural sensory potential. RESULTS: Anti-MAG/SGPG neuropathies showed: (1) more severe involvement of peroneal nerves; (2) more frequent disproportionate distal slowing of motor conductions (TLI< or =0.25) and absent sural potential, and (3) no CB. However 3/22 CIDP patients also had at least two nerves with TLI< or =0.25 and no CB. CONCLUSIONS: Electrophysiologic findings suggest in anti-MAG/SGPG neuropathy a length-dependent process with a likely centripetal evolution. A disproportionate slowing of conduction in distal segments of motor nerves suggests the diagnosis of anti-MAG/SGPG neuropathy, although it is not pathognomonic.