Does Amyotrophic Lateral Sclerosis (ALS) Have Metabolic Causes from Human Evolution?

Motor unit (MU) potentials were registered from 20 ALS patients and 13 age-matched control individuals during isometric constant force contractions of brachial biceps (BB). The registered signals were decomposed into single MU potential trains. The estimates of duration of the afterhyperpolarisation (AHP) in MNs, derived from the interspike interval variability, was compared between ALS patients (124 MNs) and control subjects (111 MNs) and no significant differences were encountered. However, the relationship between TI and age for patients appeared to be qualitatively different from that of the control group. The dependence of patients' AHPs on relative force deficit (RFD), which quantified muscle involvement, was more specific. For RFDs below 30%, the AHP estimate was significantly lower than control values and then increased thereafter with increasing RFDs. Moreover, firing rates of patients with the smallest RFDs were significantly higher while firing rates of patients with the greatest RFDs were significantly lower than control values. The AHP shortening in the early stages of muscle impairment is consistent with the decrease in firing threshold of ‘fast' MNs found in spinal cord slices from neonatal SOD1 mice. The later elongation of the AHP may be caused by the higher vulnerability of ‘fast' MNs to degeneration and by the influence of reinnervation. Our results are comparable to what has been observed in acute experiments in animal models, providing a bridge between animal and clinical research that may be relevant for identification of mechanism(s) underlying neurodegeneration in ALS.

A Stem Cell-Based Screening Platform Identifies Compounds that Desensitize Motor Neurons to Endoplasmic Reticulum Stress.

N-Glycolylneuraminic acid (NeuGc) is abundantly expressed in most mammals, but it is not detectable in humans. The expression of NeuGc is controlled by cytidine monophospho-N-acetylneuraminic acid (CMP-NeuAc) hydroxylase activity. We previously cloned a cDNA for mouse CMP-NeuAc hydroxylase and found that the human genome contains a homologue. We report here the molecular basis for the absence of NeuGc in humans. We cloned a cDNA for human CMP-NeuAc hydroxylase from a HeLa cell cDNA library. The cDNA encodes a 486-amino acid protein, and its deduced amino acid sequence lacks a domain corresponding to the N-terminal 104 amino acids of the mouse CMP-NeuAc hydroxylase protein, although the human protein is highly identical (93%) to the rest of the mouse hydroxylase protein. The N-terminal truncation of the human hydroxylase is caused by deletion of a 92-base pair-long exon in human genomic DNA. The human hydroxylase expressed in COS-7 cells exhibited no enzymatic activity, and a mouse hydroxylase mutant, which lacks the N-terminal domain, was also inactive. A chimera composed of the human hydroxylase and the N-terminal domain of the mouse hydroxylase displayed the enzyme activity. These results indicate that the human homologue of CMP-NeuAc hydroxylase is inactive because it lacks an N-terminal domain that is essential for enzyme activity. The absence of NeuGc in human glycoconjugates is due to a partial deletion in the gene that encodes CMP-NeuAc hydroxylase.

Background Pain was considered a common and neglected symptom in amyotrophic lateral sclerosis (ALS) and had a substantial impact on the quality of life of ALS patients and their caregivers. However, pain in ALS was mainly evaluated from the perspective of nociceptive pain; only three studies referred to neuropathic pain in ALS, and there has been yet no study considering the neuropathic pain characteristics in ALS patients from China. Therefore, the purpose of our study was to determine characteristics of pain (nociceptive pain and neuropathic pain) by three different types of questionnaires. The correlation between pain and clinical parameters in ALS patients was also evaluated. Methods Patients were eligible if they fulfilled the criteria of probable and definitive ALS according to the revised El Escorial criteria. Healthy normal controls, matched to ALS patients by age and gender, were recruited. Pain was evaluated by numerical pain rating scale (NRS), Brief Pain Inventory (BPI), and Douleur Neuropathique-4 (DN4) in ALS patients and controls. Physical status of ALS patients was evaluated with ALS Functional Rating Scale-revised (ALSFRS-R). Results 65 patients with sporadic ALS and 100 healthy normal controls in Southwestern China were included. Pain in the preceding week was more frequently reported by patients with ALS (30, 46.2%) than controls (36, 36%) (p = 0.193). DN4 score⩾4 was found in three ALS patients and one control (p = 0.480). Ten ALS patients (33.3%) and twenty-eight controls (77.8%) (p < 0.001) received therapy for pain. ALS patients with a DN4 score ≥ 4 had a longer disease duration and a higher PSI and PII score than ALS cases reporting nociceptive pain (p = 0.041, 0.048, and 0.027, respectively). Pain mainly interfered with ALS patients' mood, enjoyment of life, and the Pain Interference Index (PII) score. Conclusions Our findings indicated that pain in our ALS cohorts was insufficiently treated and interfered with patients' mood and enjoyment of life. Most notably, we found that ALS patients with a DN4 score⩾4 may have a longer disease duration and a higher PSI and PII score than ALS patients reporting nociceptive pain, which has never been reported, strongly deserving further validation.

Background: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. There is heterogeneity of the clinical features of ALS including site of onset and rate of progression. Previously, ALS was considered to be a disease of the motor system. However, there is evidence that ALS patients can have cognitive impairment. Some patients meet the diagnostic criteria for Frontotemporal dementia (FTD). It is now thought that FTD and ALS are related neurodegenerative disorders, which fall on the same disease spectrum. A reliable biomarker is needed to monitor the progression of the disease and assess the effects of potential therapies. Sequential Window Acquisition of all theoretical fragment-ion spectra analysis (SWATHTM) is a reliable and powerful proteomic approach to investigate the biomarker proteins in complex samples such as blood. Method: The aim of the first study is to evaluate the utility of neurofilament levels as blood or cerebrospinal fluid (CSF) biomarker in patients with ALS by using a systematic search of Pubmed, Embase and Scopus databases. Meta-analysis of the data was performed. The aim of the second study is to screen for cognitive and behavioural impairment in people with ALS and controls with neuromuscular disease and to correlate these with clinical features. 108 people with ALS and 60 controls were recruited and assessed with the Addenbrooke’s cognitive examination-III (ACE-III), the Frontal assessment battery (FAB), and the executive function component of the Edinburgh cognitive and behavioural ALS screen (ECAS). The Amyotrophic lateral sclerosis-Frontotemporal dementia questionnaire (ALS-FTD-Q) and the Motor Neuron Disease Behavioural instrument (MiND-B) were administered to the caregivers of people with ALS. Longitudinal studies of cognition were performed in 37 ALS patients. The aim of the third study is to search for plasma biomarkers in ALS patients compared to healthy controls by using SWATH™ quantification analysis and to compare proteomic analysis of ALS patients with and without cognitive impairment (CI). 42 patients with ALS and 18 healthy controls were recruited. Western blot analysis was used to confirm the results of analysis and in an independent set of samples. Ingenuity pathway analysis (IPA) was performed. Results: The systematic review found that levels of NF heavy chain and light chains were significantly elevated in the CSF of ALS patients compared to healthy controls/controls without parenchymal central nervous system (CNS) involvement and ALS mimic disease patients. NF light chain level in CSF was higher in ALS patients than in neurological patients with CNS involvement (SMD=1.352, P=0.001). NF light chain concentration in blood was higher in ALS patients than in healthy controls/controls without CNS involvement (SMD=1.448, P<0.0001). NF heavy chain levels in CSF were negatively correlated disease duration and ALSFRS-R (r=-0.447, P<0.0001; r=-0.279, P=0.011). NF light chain levels in CSF were negatively correlated with disease duration (r=-0.486, P<0.0001). In the patient cohort, the frequencies of cognitive impairment based on the ACE-III and FAB were 30.0% and 14.0%, in ALS and 11.7% and 3.3% in controls, respectively. In ALS, the frequencies of behavioural impairment based on ALS-FTD-Q and MiND-B were 32.1% and 39.4 %, respectively. ALS participants with cognitive impairment measured with ACE-III had significantly shorter survival time than those without. ALS participants with behavioural impairment measured with ALS-FTD-Q had worse prognosis than those without. No significant difference was found between the first two serial cognitive tests based on ACE-III and FAB by using a generalized estimating equation. Between ALS and controls, there were significant differences in the expression of 30 proteins. Of these, plasma gelsolin concentration was 1.2 fold higher in controls than ALS patients (P=0.006). Between controls and ALS with CI, there was significant difference in expression of 32 proteins. The clusterin level was 1.2 fold downregulated in patients with CI compared with controls (P=0.03). The observed changes in levels of gelsolin, clusterin, CD5L and ficolin 3 were validated by using western blot. Pathway analysis showed that the LXR/RXR pathway, complement pathway and coagulation pathway are regulated in ALS. Conclusions: The results of the first study shows that NF heavy and light chain levels have potential to be used as markers of neural degeneration in ALS, but are not specific for the disease, and are more likely to be used as measures of disease progression. The results of second study indicate that there is a greater frequency of cognitive impairment in people with ALS than in patients with other neuromuscular diseases. The cognitive and behavioural tests are potential biomarkers of the prognosis of ALS. The results of cognitive tests are stable over 6 months and possibly longer. The results of the third study illustrate that clusterin, gelsolin and ficolin 3 are novel potential biomarkers to differentiate the ALS patients from healthy controls. Abnormalities in the LXR/RXR pathway suggest that lipid metabolism is involved in ALS. There are widespread changes in immune function and coagulation in ALS.

Background and ObjectivesWe earlier reported elevated chemokine ligand-2 (CCL2) in Indian amyotrophic lateral sclerosis (ALS) patients. We now analysed chemokine receptor-2 (CCR2), the receptor of CCL2, in these ALS patients.MethodsIndian sporadic ALS patients (n = 50) were included on the basis of El Escorial criteria. Percentage (%) of CCR2 expressing peripheral blood mononuclear cells (PBMCs) was evaluated using Flow Cytometry. Real Time Polymerase Chain Reaction (PCR) was used to quantitate CCR2 mRNA expression in PBMCs. Normal controls (n = 40) were also included for comparison.ResultsFlow Cytometry revealed significantly reduced CCR2 expressing PBMCs in the ALS patients. We also found a significant decline in number of CCR2 expressing PBMCs in limb onset ALS when compared to bulbar onset ALS. PBMCs from ALS patients showed substantial down-regulation of CCR2 mRNA. CCR2 mRNA expression was found to be decreased among limb ALS patients as compared to bulbar onset ALS. Further, the count of CCR2+ PBMCs and CCR2 mRNA transcript in PBMCs was significantly lower in severe and moderate ALS as compared to ALS patients with mild impairments.ConclusionsDownregulation of PBMCs CCR2 may indicate its etio-pathological relevance in ALS pathogenesis. Reduced PBMCs CCR2 may result in decreased infiltration of leukocytes at the site of degeneration as a compensatory response to ALS. CCR2 levels measurements in hematopoietic stem cells and estimation of comparative PBMCs count among ALS, disease controls and normal controls can unveil its direct neuroprotective role. However, the conclusions are restricted by the absence of neurological/non-neurological disease controls in the study.

Objective: To review the phenotype of patients with ALS and FTD/ALS in c9FTD/ALS. Background A hexanucleotide repeat expansion in C9ORF72 recently reported as a major cause of familial ALS, FTD/ALS and FTD, designated c9FTD/ALS, also was found in sporadic ALS and FTD patients (doi:10.1016/j.neuron.2011.09.010; doi:10.1016/j.neuron.2011.09.011). Few data regarding the c9FTD/ALS phenotype in ALS and FTD/ALS are available. Design/Methods: 231 patients with ALS or FTD/ALS identified at the Mayo Clinic Florida ALS Center were screened for the c9FTD/ALS mutation. Patients completed a standard ALS diagnostic evaluation including EMG, and neuropsychological testing where indicated. Autopsy was performed in 5 mutation carriers. Results: Eighteen patients (15 ALS (9 male); 3 FTD/ALS (1 male; cognitive dysfunction preceded ALS in 2) representing 17 independent pedigrees had a c9FTD/ALS mutation. FTD suspected in 2/15 ALS patients was not confirmed owing to motor impairment. Nine probands reported first/second degree relatives with ALS or FTD/ALS; 5 probands reported relatives with FTD/dementia only and 2 probands reported no family history of ALS or FTD/dementia. One proband was adopted. All patients had El Escorial possible/probable/definite ALS except for a male with suspected ALS. Onset was bulbar in 2 patients (1 ALS; 1 FTD/ALS) and spinal in 16. Median onset age was 56 years (41-72yr). Median survival was 2.3 years (1-6.3yr) in 11 deceased; brain/spinal cord in 5 demonstrated TDP-43 pathology typical of ALS, with extramotor brain pathology in 2 FTD/ALS. Conclusions: The c9FTD/ALS phenotype of our patients was predominantly classical ALS with spinal onset. Frontotemporal cognitive impairment antedated motor signs in 2/3 FTD/ALS. Survival ranged from 1 to >6 years. c9FTD/ALS in 2 sporadic ALS patients may represent incomplete penetrance, incomplete ascertainment or new mutations and requires further study. Occurrence of FTD alone in family members supports consideration of FTD in first or second degree relatives of ALS patients as a potential marker of c9FTD/ALS. Supported by: ALS Association, Mayo Foundation and MCF ALS Center donor funds, NIH R01 NS065782 and R01 AG026251, NIH/NINDS 1RC2NS070276, NS057567, P50NS072187-01S2, Dystonia Medical Research Foundation, and a gift from Carl Edward Bolch, Jr., and Susan Bass Bolch. Disclosure: Dr. Boylan has nothing to disclose. Dr. DeJesus-Hernandez has nothing to disclose. Dr. Rush has nothing to disclose. Dr. Desaro has nothing to disclose. Dr. Johnston has nothing to disclose. Dr. Kryston has nothing to disclose. Dr. Rutherford has nothing to disclose. Dr. Baker has nothing to disclose. Dr. Wszolek has received personal compensation in an editorial capacity for Parkinsonism and Realted Disorders and European Journal of Neurology. Dr. Dickson has nothing to disclose. Dr. Rademakers has nothing to disclose.

Background and objectives: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the relentless loss of upper motor neurones (UMN) and lower motor neurones (LMN), leading to progressive weakness. The cause of ALS is unknown and there are currently no curative treatments. The median survival is 18 months from diagnosis, however, the rate of disease progression and survival vary significantly among individual ALS patients. In the absence of a cure for ALS, discovery of factors that modify disease progression is critical. An understanding of processes that influence the course of ALS could shed light on disease mechanisms and identify therapeutic targets that could be manipulated in order to prolong survival. Systemic energy metabolism is emerging as an important modifying factor in ALS. Of clinical significance, adiposity [in the form of fat mass (FM)] and nutritional status modify survival in ALS. Therefore, the assessment of FM and implementation of nutritional interventions to maintain FM are important components of routine care in ALS patients. Anthropometric measurements, including body mass index (BMI) and body adiposity index (BAI) are commonly used to predict adiposity in order to guide nutritional management. However, the accuracy of these measurements in ALS patients is currently unknown. Hypermetabolism [an increase in measured resting energy expenditure (REE) compared to a predicted REE] has been reported in some ALS patients and is also a possible modifier of disease progression. If this is a causal relationship, then strategies to correct or compensate for increased energy expenditure could possibly modify disease course. However, further studies to clarify the incidence, clinical correlations and consequences of hypermetabolism must be established. The objectives of this thesis were to determine whether commonly used anthropometric measurements are accurate predictors of FM in ALS patients and to study the incidence and clinical correlations of hypermetabolism in ALS patients. Methodology and main findings: Anthropometric measurements of BMI and BAI were compared to percentage FM derived from air displacement plethysmography (ADP) in 44 ALS patients and 35 age- and sex- matched healthy controls. Using Bland-Altman analyses it was found that both anthropometric measurements were less accurate predictors of FM in ALS patients than in controls and that BMI and BAI provided a poor estimate of FM in ALS patients. In a longitudinal assessment of 29 ALS patients, neither BMI nor BAI consistently reflected the change in FM. These results indicate that an isolated measure of BMI and BAI is not an accurate indicator of adiposity in ALS and that longitudinal measurements could be misleading. REE was measured via indirect calorimetry (mREE) and compared to a predicted REE (pREE, derived from a model that accounts for body composition) in 50 ALS patients and 50 age- and sex- matched healthy controls. Hypermetabolism was defined as a metabolic index (mREE/pREE x100) ≥ 120. Individuals with a metabolic index <120 were considered to be normometabolic. Hypermetabolism was found in 16% of controls and 40% of ALS patients. Hypermetabolic ALS patients had a higher LMN disease burden (assessed by clinical examination) and a greater short-term functional decline (assessed by the revised ALS functional rating scale, ALSFRS-R) than normometabolic patients. Conclusions and future directions: This study found that in ALS patients, BMI and BAI are not accurate predictors of FM and that they provide a poor indicator of change in FM over time. It is therefore likely that changes in BMI and BAI in ALS patients occur independent to changes in FM alone and could depend on muscle atrophy and re-distribution of fat. It was also found that when body composition is accounted for, the incidence of hypermetabolism is greater in ALS patients than in healthy matched controls. An association between hypermetabolism and LMN disease burden was observed in ALS patients. As LMN disease burden reflects dysfunction of motor units, it is hypothesized that hypermetabolism in ALS could arise from abnormal motor units which include dysfunctional LMNs, disrupted neuromuscular junctions and denervated muscle. Furthermore, hypermetabolism was associated with a greater functional decline in ALS patients who were studied over time. In the light of these findings it is hypothesized that hypermetabolism could drive progression of ALS and lead to a vicious cycle of denervation, hypermetabolism and further disease progression. Overall, the results of this thesis suggest that BMI and BAI are inadequate markers of nutritional status in ALS and that hypermetabolism is an important metabolic consideration in ALS patients. More accurate ALS-specific predictors of FM are required to guide nutritional therapies and further clinical and physiological studies are needed to understand the cause and prognostic implications of changes in body composition and hypermetabolism.

Objective To investigate the diagnostic value of the split-hand sign in amyotrophic lateral sclerosis (ALS). Methods Ninety ALS patients, 41 patients with other neuromuscular disorders and 71 normal controls were recruited for conventional nerve conduction study. Compound muscle action potential (CMAP) amplitude recorded from abductor pollicis brevis (APB), abductor digiti minimi (ADM) and first dorsal interosseous (FDI), CMAP amplitude ratios, CMAP amplitude differences and split-hand index (SI) were analyzed. Results The APB/ADM CMAP amplitude ratio was significantly lower in the ALS patients (0.44(0.44)) than that in the patients with other neuromuscular disorders (1.31(0.87); z=6.967, P<0.01) and the normal controls (0.99(0.42); z=7.687, P<0.01). The FDI/ADM CMAP amplitude ratio was significantly decreased in the ALS patients (0.79(0.46)) compared with that in the normal controls (1.23(0.39); z=5.899, P<0.01). The FDI/ADM CMAP amplitude ratio was comparable between the ALS patients and the patients with other neuromuscular disorders (0.93(0.62); z=1.737, P=0.081). SI was significantly lower in the ALS patients (2.42(3.14)) than that in the patients with other neuromuscular disorders (10.10(6.54); q=7.947, P<0.05) and the normal controls (17.93(8.32); q=10.827, P<0.05). SI <5.2 can help differentiate ALS from mimic disorders, with a sensitivity of 83.33% and specificity of 96.43%. Conclusions The split-hand sign appears to be a specific feature of ALS. SI robustly differentiates ALS from mimic disorders and potentially facilitates an earlier diagnosis of ALS. Key words: Amyotrophic lateral sclerosis; Split-hand sign; Split-hand index; Nerve conduction study

Background: Mutations in the genes encoding the heterogeneous nuclear ribonucleoproteins hnRNPA1 and hnRNPA2/B1 have been reported in a multisystem proteinopathy that includes amyotrophic lateral sclerosis (ALS) and inclusion body myopathy associated with Paget disease of the bone and frontotemporal dementia. Mutations were also described in the prion-like domain of hnRNPA1 in patients with classic ALS. Another hnRNP protein, hnRNPA3, has been found to be associated with the ALS/frontotemporal dementia protein C9orf72. Objective: To further assess their role in ALS, we examined these hnRNPs in spinal cord tissue from sporadic (SALS) and familial ALS (FALS) patients, including C9orf72 repeat expansion-positive patients, and controls. We also sought to determine the prevalence of HNRNPA1, HNRNPA2B1, and HNRNPA3 mutations in Australian ALS patients. Methods: Immunostaining was used to assess hnRNPs in ALS patient spinal cords. Mutation analysis of the HNRNPA1, HNRNPA2B1, and HNRNPA3 genes was performed in FALS and of their prion-like domains in SALS patients. Results: Immunostaining of spinal motor neurons of ALS patients with the C9orf72 repeat expansion showed significant mislocalisation of hnRNPA3, and no differences in hnRNPA1 or A2/B1 localisation, compared to controls. No novel or known mutations were identified in HNRNPA1, HNRNPA2B1, or HNRNPA3 in Australian ALS patients. Conclusions: hnRNPA3 pathology was identified in motor neurons of ALS patients with C9orf72 repeat expansions, implicating hnRNPA3 in the pathogenesis of C9orf72-linked ALS. hnRNPA3 warrants further investigation into the pathogenesis of ALS linked to C9orf72. This study also determined that HNRNP mutations are not a common cause of FALS and SALS in Australia.

ObjectiveTo study the frequency and clinical features of sleep disturbances in amyotrophic lateral sclerosis (ALS) patients and compare sleep disorders between ALS with and without mutations.MethodsIn this case–control study, 204...

Fibrosis as a common trait in amyotrophic lateral sclerosis tissues.

BackgroundN-glycolylneuraminic acid (Neu5Gc) is synthesized from its precursor N-acetylneuraminic acid (Neu5Ac) by cytidine-5′-monophospho-N acetylneuraminic acid hydroxylase (CMAH), which is encoded by the CMAH gene. Most mammals have both Neu5Gc and Neu5Ac, but humans and ferrets have only Neu5Ac because of loss-of-function mutations. Dogs and cats are polymorphic for Neu5Gc and Neu5Ac expression like cats, in which the CMAH gene is responsible for the AB Blood group system. Although the CMAH gene has been characterized in many species, not much is known about it in dogs. In this study, we cloned the dog CMAH cDNA, and performed mRNA expression analysis of this gene in several organs. We also identified single nucleotide polymorphisms (SNPs) in the CMAH gene.ResultsWe cloned the 1737-bp open reading frame of the dog CMAH gene. This gene consists of at least 14 coding exons and codes for a polypeptide of 578 amino acids and is located on chromosome 35. The amino acid identities of dog CMAH with the corresponding sequences from cat, pig, chimpanzee, mouse, and rat were high (89 to 93%). RT-PCR analysis showed that the dog CMAH cDNA was expressed in various tissues. We identified four exonic SNPs (three synonymous and one non-synonymous), 11 intronic SNPs, and an indel in 11 dog breeds by analyzing the nucleotide sequences of the 14 exons, including the coding region of CMAH. In the genotype of the non-synonymous SNP, c.554 A > G (p.Lys185Arg), in a total of 285 dogs of seven different breeds, the allele G was widely distributed, and the allele A was the most frequent in the Shiba dogs. The dogs expressing Neu5Ac did not carry the loss-of-function deletion of CMAH found in humans and ferrets, and it remains unclear whether the point mutations influence the expression of Neu5Ac.ConclusionsWe characterized the canine CMAH gene at the molecular level for the first time. The results obtained in this study provide essential information that will help in understanding the molecular roles of the CMAH gene in canine erythrocyte antigens.

BackgroundVascular endothelial growth factor-A (VEGF-A) and chemokne ligand-2 (CCL2) levels have been examined in Amyotrophic Lateral Sclerosis (ALS) patients in Western countries. We measured these values in North Indian ALS patients, since these patients display considerably enhanced survival duration.MethodsSporadic ALS patients were included on the basis of El Escorial criteria. VEGF-A and CCL2 levels were analyzed in serum and cerebrospinal fluid (CSF) of 50 ALS patients using enzyme linked immunosorbent assay (ELISA) and compared with normal controls. Their levels were adjusted for possible confounders like cigarette smoking, alcohol and meat consumption.ResultsContrary to previous studies, VEGF-A was found to be elevated significantly in serum and CSF in ALS patient population studied. We also found an increase in CCL2 levels in CSF of these ALS patients. Serum and CSF from definite ALS revealed higher VEGF-A as compared to probable and possible ALS. CCL2 was unaltered between definite, probable and possible ALS. Univariate and multivariate analysis revealed a lack of association of smoking, alcohol and meat consumption with VEGF-A and CCL2 levels.ConclusionsVEGF-A upregulation may indicate an activation of compensatory responses in ALS which may reflect or in fact account for increased survival of North Indian ALS patients after disease onset. The intrathecal synthesis of CCL2 suggests the involvement of adult neural stem cells and microglial activation in ALS pathogenesis which needs further investigation.

Objective To investigate the characteristics of giant F-waves in patients with amyotrophic lateral sclerosis (ALS) and the relationship between giant F-waves and disease phenotype. Methods Motor nerve conduction study and F-waves were performed to the median, ulnar, tibial and peroneal nerves of 55 patients with ALS and 52 healthy volunteers. A series of 100 electrical stimuli were employed to obtain F-waves. The following F-wave variables were estimated: frequency of giant F-waves, frequency of patients with giant F-waves, the relationship between giant F-waves and lower motor neuron dysfunction, the relationship between giant F-waves and upper motor neuron dysfunction, the relationship between giant F-waves and disease duration, the relationship between giant F-waves and disease severity, and the relationship between giant F-waves and disease progression rate (DPR). Results The frequencies of giant F-waves (ALS: median nerve 0.00(0.00)%, ulnar nerve 0.00(1.02)%, tibial nerve 0.00(0.00)%, peroneal nerve 0.00(0.00)%. Normal controls: median nerve 0.00(0.00)%, Z=-2.360, P=0.018; ulnar nerve 0.00(0.00)%, Z=-3.997, P<0.01; tibial nerve 0.00(0.00)%, Z=-3.006, P=0.003; peroneal nerve 0.00(0.00)%, Z=-3.006, P=0.003) and the frequencies of patients with giant F-waves (ALS: median nerve 13/55, 23.6%, ulnar nerve 26/55, 47.2%, tibial nerve 18/55, 32.7%, peroneal nerve 16/55, 29.1%. Normal controls: median nerve 4/52, 7.7%, χ2=0.024, P=0.024; ulnar nerve 7/52, 13.5%, χ2=14.326, P<0.01; tibial nerve 6/52, 11.5%, χ2=6.897, P=0.009; peroneal nerve 6/52, 11.5%, χ2=5.042, P=0.025) in the median nerve, ulnar nerve, tibial nerve and peroneal nerve were significantly increased compared with those of the normal controls. No significant differences were found in the frequencies of upper motor neuron dysfunction between nerves with giant F-waves and nerves without giant F-waves in the median nerves, ulnar nerves, tibial nerves and peroneal nerves of ALS patients. The compound muscle action potential amplitude of nerves with giant F-waves was significantly higher than those of nerves without giant F-waves in the median nerves (11.20(5.80) mV vs 5.90(8.50) mV, t=2.883, P=0.004)and tibial nerves ((13.20±4.61) mV vs (10.69±4.76) mV, t=-2.222, P=0.028)of the ALS patients. No significant correlation was detected between the frequency of giant F-waves and disease duration or ALS functional rating scale in the ALS patients, while the frequency of giant F-waves correlated inversely with the DPR(r=-0.287, P=0.034). No significant differences were detected in disease duration between ALS patients with giant F-waves and those without giant F-waves. Compared with those in ALS patients without giant F-waves, the revised ALS Functional Rating Scale score (37.00(3.00) vs 42.00(4.75), Z=3.197, P=0.001) was more, the DPR (0.50(0.35)vs 0.90(0.43), Z=-3.033, P=0.002) was slower in ALS patients with giant F-waves. Conclusions The giant F-waves were significantly increased in the ALS patients than those in the healthy volunteers and were distributed asymmetrically between the left and right sides. These electrophysiological characteristics of ALS patients fitted well with progressive loss of anterior horn cells, and indicated differential involvement of different spinal motoneuron pools in the ALS patients. No correlations were found between the frequency of giant F-waves and disease duration. The appearance of giant F-waves may indicate loss of spinal motoneuron early in the disease course, and may suggest that the degree of reinnervation and functional compensation are relatively good after motoneuron loss. Key words: Amyotrophic lateral sclerosis; Neural conduction; F-wave