Involvement of peripheral sensory fibers in amyotrophic lateral sclerosis: electrophysiological study of 64 cases

Electrodiagnostic findings in amyotrophic lateral sclerosis: Variation with region of onset and utility of thoracic paraspinal muscle examination

INTRODUCTION/AIMS

Limited data exist regarding variation of electrodiagnostic (EDX) findings in amyotrophic lateral sclerosis (ALS) patients with different onset regions and specificity of thoracic paraspinal muscle (TPSP) examination for confirming a diagnosis of ALS. We aimed to demonstrate the variation of EDX features and characterize the utility of TPSP muscle examination in the electrodiagnosis of ALS.

METHODS

This is a retrospective study of a large cohort of ALS patients who had a comprehensive EDX evaluation.

RESULTS

The study included 448 patients; all fulfilled the Gold Coast criteria for ALS. The average age at the time of EDX study was 64 years, and 41.1% were women. The onset region was identified as follows: bulbar (N = 149), cervical (N = 127), lumbosacral (N = 162), and other (N = 10). In contrast to limb onset, bulbar-onset patients more frequently demonstrated a pattern of normal or near normal needle electromyography (EMG) (p < .0001) and less frequently had abnormalities on EMG of TPSP (p = .002). Clinical or EDX diagnosis of sensory polyneuropathy was present in 12.6% patients, more frequently in the lumbosacral onset subgroup (p < .03). EMG showed active denervation in 9.6% and chronic denervation in 59% of craniobulbar muscles examined, without observed difference among different onset regions. TPSP showed higher frequencies of active and chronic denervation in ALS than a group of patients with non-ALS neuromuscular disorders.

DISCUSSION

EDX features may differ among ALS patients of different onset regions. TPSP EMG is highly useful in differentiating ALS from non-ALS neuromuscular disorders while the yield of craniobulbar muscles, especially for active denervation, is low.

Sensory neuropathy in amyotrophic lateral sclerosis: a systematic review

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the degeneration of both upper and lower motoneurons, leading to motor and non-motor symptoms. Recent evidence suggests that ALS is indeed a multisystem disorder, associated with cognitive impairment, dysautonomia, pain and fatigue, excess of secretions, and sensory symptoms. To evaluate whether sensory neuropathy could broaden its spectrum, we systematically reviewed its presence and characteristics in ALS, extracting data on epidemiological, clinical, neurophysiological, neuropathological, and genetic features. Sensory neuropathy can be found in up to 20% of ALS patients, affecting both large and small fibers, although there is a great heterogeneity related to different techniques used for its detection (electromyography vs skin biopsy vs nerve biopsy). Moreover, the association between CIDP-like neuropathy and ALS needs to be better explored, although it could be interpreted as part of the neuroinflammatory process in the latter disease. Sensory neuropathy in ALS may be associated with a spinal onset and might be more frequent in SOD1 patients. Moreover, it seems mutually exclusive with cognitive impairment. No associations with sex and other genetic mutation were observed. All these data in the literature reveal the importance of actively looking for sensory neuropathy in ALS patients, and suggest including sensory neuropathy among ALS non-motor features, as it may explain sensory symptoms frequently reported throughout the course of the disease. Its early identification could help avoid diagnostic delays and improve patients' treatment and quality of life.

Small-fibre Neuropathy in Patients with Familial Amyotrophic Lateral Sclerosis Type 8

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a degenerative disease of the nervous system that primarily affects motor neurons. ALS type 8 (ALS8) is a familiar form with predominant involvement of lower motor neurons, tremor, and slow progression.

OBJECTIVE

The aim of this study was to describe sensory involvement in a cohort of ALS8 patients and compare it with the characteristics of sporadic ALS (sALS) patients and controls.

METHODS

We compared data from 40 ALS8 and 10 sALS patients assessed by neurological evaluation and electrophysiological study. Skin biopsies were performed in these patients and 12 controls for analysis of intraepidermal nerve fiber (IENF) density by protein gene product 9.5 (PGP 9.5) immunohistochemistry.

RESULTS

The ALS8 group was younger than the sALS group at the onset of symptoms (p < 0.05) and had a longer disease evolution (p < 0.01). Sensory abnormalities were evident in 35% of the ALS8 and 30% of the sALS patients by neurological examination, and all ALS patients presented normal sensory nerve action potentials. Despite being similar in the ALS8 and sALS groups, IENF density in the ALS8 group was lower than that in the controls (p < 0.0005). In the ALS8 group, IENF density was significantly lower in patients with impairment of vibratory sensation than in those without this finding (p < 0.05) and in females than in males (p < 0.05).

CONCLUSION

Sensory impairment and decreased IENF density are present in ALS8 patients at a frequency and intensity similar to that in the sALS group.

Sensory Involvement in Amyotrophic Lateral Sclerosis

Although amyotrophic lateral sclerosis (ALS) is pre-eminently a motor disease, the existence of non-motor manifestations, including sensory involvement, has been described in the last few years. Although from a clinical perspective, sensory symptoms are overshadowed by their motor manifestations, this does not mean that their pathological significance is not relevant. In this review, we have made an extensive description of the involvement of sensory and autonomic systems described to date in ALS, from clinical, neurophysiological, neuroimaging, neuropathological, functional, and molecular perspectives.

Clinical and electrophysiological findings in C9ORF72 ALS

INTRODUCTION/AIMS

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal, neurodegenerative disorder of motor neurons in which the cause is mostly unknown. Early identification of genetic ALS cases, of which C9ORF72 (C9ALS) is the most frequent, can have important implications for evaluation, prognosis, and therapeutics. Here, we aimed to characterize the clinical and electrophysiological hallmarks of C9ALS and investigate differences from C9ORF72 negative ALS (non-C9ALS).

METHODS

We retrospectively reviewed clinical and electrodiagnostic (EDX) data for all genetically confirmed C9ALS cases seen between 1/1/2012 and 10/1/2020 who met Gold Coast criteria and compared them 1:1 with non-C9ALS patients within the same time frame.

RESULTS

A total of 99 C9ALS and 99 non-C9ALS cases were identified. Compared to non-C9ALS, C9ALS demonstrated higher prevalence in women, lesser racial variability, stronger family history of ALS, and higher frequency of upper motor neuron signs. EDX testing of C9ALS showed higher median sensory nerve and lower fibular compound muscle action potential amplitudes.

DISCUSSION

Although the differences between C9ALS and non-C9ALS reached statistical significance in certain nerve conduction parameters, they were not sufficient to discriminate between groups on a case-by-case basis. Genetic testing is required to identify C9ALS patients.

Interrogating interneurone function using threshold tracking of the H reflex in healthy subjects and patients with motor neurone disease

OBJECTIVE

The excitability of the lower motoneurone pool is traditionally tested using the H reflex and a constant-stimulus paradigm, which measures changes in the amplitude of the reflex response. This technique has limitations because reflex responses of different size must involve the recruitment or inhibition of different motoneurones. The threshold-tracking technique ensures that the changes in excitability occur for an identical population of motoneurones. We aimed to assess this technique and then apply it in patients with motor neurone disease (MND).

METHODS

The threshold-tracking approach was assessed in 17 healthy subjects and 11 patients with MND. The soleus H reflex was conditioned by deep peroneal nerve stimulation producing reciprocal Ia and so-called D1 and D2 inhibitions, which are believed to reflect presynaptic inhibition of soleus Ia afferents.

RESULTS

Threshold tracking was quicker than the constant-stimulus technique and reliable, properties that may be advantageous for clinical studies. D1 inhibition was significantly reduced in patients with MND.

CONCLUSIONS

Threshold tracking is useful and may be preferable under some conditions for studying the excitability of the motoneurone pool. The decreased D1 inhibition in the patients suggests that presynaptic inhibition may be reduced in MND.

SIGNIFICANCE

Reduced presynaptic inhibition could be evidence of an interneuronopathy in MND. It is possible that the hyperreflexia is a spinal pre-motoneuronal disorder, and not definitive evidence of corticospinal involvement in MND.

The Peripheral Nervous System in Amyotrophic Lateral Sclerosis: Opportunities for Translational Research

Although amyotrophic lateral sclerosis (ALS) has been considered as a disorder of the motor neuron (MN) cell body, recent evidences show the non-cell-autonomous pathogenic nature of the disease. Axonal degeneration, loss of peripheral axons and destruction of nerve terminals are early events in the disease pathogenic cascade, anticipating MN degeneration, and the onset of clinical symptoms. Therefore, although ALS and peripheral axonal neuropathies should be differentiated in clinical practice, they also share damage to common molecular pathways, including axonal transport, RNA metabolism and proteostasis. Thus, an extensive evaluation of the molecular events occurring in the peripheral nervous system (PNS) could be fundamental to understand the pathogenic mechanisms of ALS, favoring the discovery of potential disease biomarkers, and new therapeutic targets.

Excitability of sensory axons in amyotrophic lateral sclerosis

OBJECTIVE

To evaluate the excitability of sensory axons in patients with amyotrophic lateral sclerosis (ALS).

METHODS

Comprehensive sensory nerve excitability studies were prospectively performed on 28 sporadic ALS patients, compared to age-matched controls. Sensory nerve action potentials were recorded from digit 2 following median nerve stimulation at the wrist. Disease severity was measured using motor unit number estimation (MUNE), the revised ALS Functional Rating Scale (ALSFRS-R) and the MRC scale.

RESULTS

There were no significant differences in standard and extended measures of nerve excitability between ALS patients and controls. These unchanged excitability measures included accommodation to long-lasting hyperpolarization and the threshold changes after two supramaximal stimuli during the recovery cycle. Excitability parameters did not correlate with MUNE, ALSFRS-R, APB MRC scale or disease duration.

CONCLUSIONS

This cross-sectional study has identified normal axonal membrane properties in myelinated sensory axons of ALS patients. Previously described sensory abnormalities could be the result of axonal fallout, possibly due to a ganglionopathy, or to involvement of central sensory pathways rostral to gracile and cuneate nuclei.

SIGNIFICANCE

These results demonstrate the absence of generalized dysfunction of the membrane properties of sensory axons in ALS in the face of substantial deficits in motor function.

Abnormal cortical brain integration of somatosensory afferents in ALS

OBJECTIVES

Infraclinical sensory alterations have been reported at early stages of amyotrophic lateral sclerosis (ALS). While previous studies mainly focused on early somatosensory evoked potentials (SEPs), late SEPs, which reflect on cortical pathways involved in cognitive-motor functions, are relatively underinvestigated. Early and late SEPs were compared to assess their alterations in ALS.

METHODS

Median and ulnar nerves were electrically stimulated at the wrist, at 9 times the perceptual threshold, in 21 ALS patients without clinical evidence of sensory deficits, and 21 age- and gender-matched controls. SEPs were recorded at the Erb point using surface electrodes and using a needle inserted in the scalp, in front of the primary somatosensory area (with reference electrode on the ear lobe).

RESULTS

Compared to controls, ALS patients showed comparable peripheral (N9) and early cortical component (N20, P25, N30) reductions, while the late cortical components (N60, P100) were more depressed than the early ones.

CONCLUSIONS

The peripheral sensory alteration likely contributed to late SEP depression to a lesser extent than that of early SEPs.

SIGNIFICANCE

Late SEPs may provide new insights on abnormal cortical excitability affecting brain areas involved in cognitive-motor functions.

Electrophysiological and spinal imaging evidences for sensory dysfunction in amyotrophic lateral sclerosis

OBJECTIVES

The prevalence of sensory impairment at an early stage of amyotrophic lateral sclerosis (ALS) is still debated. The study aim was to investigate the anatomofunctional properties of sensory pathways in patients with ALS, combining spinal diffusion tensor imaging (DTI) and somatosensory evoked potentials (SEPs).

DESIGN

Case-control study.

SETTINGS

ALS referral centre and laboratory of biomedical imaging (Paris, France).

PARTICIPANTS

Well-characterised group of 21 patients with ALS with moderate disability (mean amyotrophic lateral sclerosis Functional Rating Scale (ALSFRS) score 39.3±1.0) and no clinical sensory signs and control group of 21 gender and age-matched healthy subjects.

OUTCOME MEASURES

Fractional anisotropy and diffusivity of the dorsal columns at C5-T1 levels (DTI metrics) and SEPs after median and ulnar nerve stimulations (latency and amplitude of N9 and N20 components).

RESULTS

Abnormal DTI metrics indicated anatomical damages of ascending sensory fibres in ∼60% of patients (p<0.05). Raw SEPs (μV) were smaller in ∼40% of patients but the difference with healthy subjects was not significant (p>0.16). Their normalisation to prestimulus activity strengthened the difference between groups (p<0.05) and allowed identification of ∼60% of patients with abnormal values. According to N9 latency, the peripheral conduction time was normal in patients (p>0.32) but based on N20 latency, the central conduction time (between spinal cord and parietal cortex) was found to be slower (p<0.05). Significant correlation was found between DTI metrics and N9 amplitude (p<0.05). Altered SEPs were also correlated with the disease duration (p<0.05). Taken together, spinal imaging and electrophysiology helped to identify ∼85% of patients with subclinical sensory defect while separated methods revealed abnormal values in ∼60%.

CONCLUSIONS

Sensory impairments have been underestimated at early stages of ALS. These results show for the first time the interest to combine electrophysiology and imaging to assess non-motor system involvement in ALS.

TRIAL REGISTRATION NUMBER

IDRCB2012-A00016-37.

Electrodiagnosis in persons with amyotrophic lateral sclerosis

Electrophysiology remains an important tool in the evaluation of patients presenting with signs and symptoms of motor neuron disease. The electrodiagnostic study should include peripheral nerve conduction studies and needle electromyography to both exclude treatable disease and gather evidence regarding a diagnosis of amyotrophic lateral sclerosis (ALS). The recent changes in the revised El Escorial criteria, recommended by the Awaji-shima consensus group, have increased the diagnostic significance of fasciculation potentials to equal that of fibrillation and positive sharp-wave potentials in the needle electromyography examination of patients suspected of having ALS. In addition, electrophysiologic evidence is now considered equivalent to clinical signs and symptoms in reaching a diagnostic certainty of ALS. These changes, strategies for the design, and implementation of an effective electrodiagnostic evaluation, in addition to electrophysiologic techniques and their relationship to the evaluation of a patient with ALS, are reviewed and discussed.

Patterns of spontaneous brain activity in amyotrophic lateral sclerosis: a resting-state FMRI study

By detecting spontaneous low-frequency fluctuations (LFF) of blood oxygen level–dependent (BOLD) signals, resting-state functional magnetic resonance imaging (rfMRI) measurements are believed to reflect spontaneous cerebral neural activity. Previous fMRI studies were focused on the examination of motor-related areas and little is known about the functional changes in the extra-motor areas in amyotrophic lateral sclerosis (ALS) patients. The aim of this study is to investigate functional cerebral abnormalities in ALS patients on a whole brain scale. Twenty ALS patients and twenty age- and sex-matched healthy volunteers were enrolled. Voxel-based analysis was used to characterize the alteration of amplitude of low frequency fluctuation (ALFF). Compared with the controls, the ALS patients showed significantly decreased ALFF in the visual cortex, fusiform gyri and right postcentral gyrus; and significantly increased ALFF in the left medial frontal gyrus, and in right inferior frontal areas after grey matter (GM) correction. Taking GM volume as covariates, the ALFF results were approximately consistent with those without GM correction. In addition, ALFF value in left medial frontal gyrus was negatively correlated with the rate of disease progression and duration. Decreased functional activity observed in the present study indicates the underlying deficits of the sensory processing system in ALS. Increased functional activity points to a compensatory mechanism. Our findings suggest that ALS is a multisystem disease other than merely motor dysfunction and provide evidence that alterations of ALFF in the frontal areas may be a special marker of ALS.

Clinical analysis and outcomes of amyotrophic lateral sclerosis with demyelinating polyneuropathy

Abnormalities of both motor and sensory nerve action potentials, similar to those found in demyelinating polyneuropathy, may occur in patients with amyotrophic lateral sclerosis (ALS). We analyzed the clinical features of unusual ALS patients with demyelinating polyneuropathy (DPN) to delineate the characteristics and outcomes of this rare condition. We reviewed three ALS patients with DPN who were confirmed to meet the electrophysiological nerve conduction criteria for DPN among 157 patients with ALS. At the initial neurological examination, one patient had both subjective sensory symptoms and abnormal results of sensory examinations, and one patient had sensory symptoms. Motor weakness of the limbs was present in all patients, and fasciculation was present in two patients. Anti-GalNAc-GD1a IgG antibodies were evident in one. Sural nerve biopsy showed a moderate, marginal reduction in myelin thickness, and teased fiber analysis revealed segmental demyelination and remyelination, but axonal degeneration was found in one patient. The mean interval from disease onset to respiratory failure or death in our three patients and seven previously documented ALS patients with DPN was 43.1 ± 18.7 months. Our findings suggest that survival in ALS with DPN is similar to that in classic ALS.

Vasculitis-like neuropathy in amyotrophic lateral sclerosis unresponsive to treatment

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease with variable involvement of other systems. A pathogenetic role of immune-mediated mechanisms has been suggested. We retrospectively analyzed sural nerve pathology and the clinical course in 18 patients with ALS. These patients had undergone sural nerve biopsy because of clinical or neurophysiological signs indicating sensory involvement (ALS+). Eleven of the 18 ALS+ patients had inflammatory cell infiltrates (ALS(vasc)) resembling infiltrates seen in patients with vasculitic neuropathy. Data were compared with the 7 patients without vasculitic infiltrates (ALS(nonvasc)) and with those of 16 patients with isolated peripheral nerve vasculitis (NP(vasc)). Biopsy specimens were processed with standard histological stains and with immunohistochemistry for a panel of inflammatory markers, with the hypothesis that the composition of infiltrates should differ between ALS(vasc) and NP(vasc). Immunoreactive cells were quantified in a blinded manner. Unlike patients with NP(vasc), those with ALS(vasc) had only minor neurophysiological abnormalities in the sural nerve and, except for the infiltrates, almost normal nerve morphology on semithin sections. The difference in epineurial T cell count was significant between ALS(vasc) and ALS(nonvasc) (p = 0.031). Surprisingly, the cellular composition of epineurial infiltrates in sural nerve biopsies was indistinguishable between ALS(vasc) and NP(vasc) despite a significant difference in fiber pathology (p < 0.0001). Standard immunosuppressive treatment did not prevent clinical progression of the motor neuron disease in any of the patients with ALS(vasc). ALS(vasc) appears as a neuropathological subtype in ALS+ suggesting immune-mediated disease components but without response to standard immunosuppressive treatment.

Selective overexpression of gamma1 laminin in astrocytes in amyotrophic lateral sclerosis indicates an involvement in ALS pathology

Our earlier studies indicate that the KDI tripeptide of gamma1 laminin reverts paralysis and protects adult rat CNS from excitotoxicity of glutamate and from oxidative stress. Here we show that gamma1 laminin is selectively overexpressed in reactive astrocytes of the amyotrophic lateral sclerosis (ALS) spinal cord, with both gray and white matter astrocytes overexpressing gamma1 laminin. Intensely gamma1 laminin-positive, aggressive-looking reactive astrocytes of the lateral columns of both cervical and thoracic spinal cord surround the lateral ventral horns and roots and extend into the area of the lateral corticospinal tract. In the cervical ALS spinal cord, large numbers of strongly gamma1 laminin-immunoreactive astrocytes are also present in the dorsal columns of the ascending sensory pathways. No other laminin or any other ALS-associated protein localizes in this manner. This unique distribution of gamma1 laminin-immunoreactive astrocytes in the ALS white matter together with our recent results on the efficacy of the KDI domain as a neuronal protector strongly suggest that gamma1 laminin may be expressed by astrocytes of the ALS spinal cord as a protective measure intended to aid neuronal survival. Further comparative studies on ALS spinal cord tissues and those of the animal models of ALS are needed to clarify the specific role of gamma1 laminin and its KDI domain in ALS and its putative interactions with the additional ALS-associated factors, such as excitotoxicity, oxidative stress, and neurofilament accumulation. Most importantly, further studies are urgently needed to test the potential of the KDI tripeptide as a therapeutic treatment for ALS.

Amyotrophic lateral sclerosis with sensory neuropathy: part of a multisystem disorder?

Sensory involvement is thought not to be a feature of amyotrophic lateral sclerosis (ALS). However, in the setting of a specialist motor neuron disease clinic, we have identified five patients with sporadic ALS and a sensory neuropathy for which an alternative cause could not be identified. In three individuals, sensory nerve biopsy was performed, demonstrating axonal loss without features of an alternative aetiology. These findings support the hypothesis that ALS is a multisystem neurodegenerative disorder that may occasionally include sensory neuropathy among its non-motor features.

Generalised sensory system abnormalities in amyotrophic lateral sclerosis: a European multicentre study

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is defined as a disease of the motor neurones, although several studies indicate involvement of the sensory nervous system.

AIM

To evaluate the sensory nerve conduction studies (NCS) in 88 patients with ALS as part of a European multicentre study.

METHODS

Seven European clinical neurophysiologists examined consecutive series of ALS patients. The examinations were peer reviewed, and the diagnosis of ALS was confirmed clinically.

RESULTS

20 (22.7%) patients with ALS had sensory NCS abnormalities in at least one nerve. Of those, 11 (12.5% of all patients) obtained an additional peer review diagnosis of electrophysiological polyneuropathy. There was no difference between the subgroups of patients with normal versus abnormal sensory NCS findings with respect to age, duration and region of onset.

CONCLUSION

The findings support previous reports of sensory involvement in ALS, and raise the question of whether patients with ALS with sensory nerve abnormalities represent a variant of ALS. ALS associated with generalised sensory system abnormalities may be consistent with degeneration of motor neurones and dorsal root ganglion cells.

A study of three patients with amyotrophic lateral sclerosis and a polyneuropathy resembling CIDP

We report three patients with a syndrome that fulfilled clinical and laboratory criteria for definite chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) who failed immunosuppressive treatment and eventually developed progressive amyotrophic lateral sclerosis (ALS). Mean disease duration was 23 months (13-38) before death. Two patients had a family history of ALS without mutations of the SOD1 gene. Postmortem examination in one patient showed an endoneurial infiltration of mononuclear cells in lumbar roots and distal and proximal peripheral nerves, mainly around myelinated fibers, with demyelination and axonal loss, consistent with CIDP. The spinal cord revealed severe neuronal loss in the anterior horn, axonal loss in the corticospinal tract, and large numbers of phagocytes in the anterior and lateral tracts, indicative of ALS. Whether demyelinating polyneuropathy was coincident with ALS or was a cause or consequence of motor neuron degeneration in these patients remains to be elucidated. This unusual combination may provide an important clue in elucidating the pathogenesis of ALS in some patients.

Nerve conduction studies in amyotrophic lateral sclerosis

We studied 137 ulnar nerves and abductor digiti minimi (ADM) muscles in 70 patients with amyotrophic lateral sclerosis (ALS), and correlated the results with ADM strength graded on the Medical Research Council (MRC) scale, to address the potential value of a standardized neurophysiological assessment of this nerve-muscle system. The ulnar nerves of 35 normal subjects matched for age, gender, and height served as controls. Reduced compound muscle action potential (CMAP) amplitude and area in the ADM muscle recordings correlated strongly with weakness. Distal motor latency, proximal conduction time, and F-wave frequency were abnormal with minimally detectable weakness. In weaker ADM muscles, conduction velocities and F-wave latencies were also abnormal. Conduction block was never observed and sensory potentials were normal. An "ALS neurophysiological index" was derived from these ulnar nerve studies and consisted of the expression: (CMAP amplitude/DML) x F frequency -, where F frequency was expressed as the number of F responses recorded in 20 trials. This index was strongly correlated with ADM weakness (r = 0.74, P < 0.001). Neurophysiological studies restricted to a single nerve-muscle system, the ulnar nerve/ADM, appear potentially useful in objectively assessing change in ALS.

Multisystem neuronal involvement and sicca complex: broadening the spectrum of complications

We report two patients with multisystem neuronal involvement associated with sicca complex. One had a lower motor neuron syndrome combined with a flaccid bladder and rectum. The second patient had unilateral hearing loss, sensory neuronopathy, Adie's pupils, upper motor neuron signs, and autopsy-proven anterior horn cell degeneration. Our cases lead us to propose that the spectrum of neuronal involvement occurring with sicca syndrome may be wider than is currently appreciated.

Focal sensory nerve abnormalities in patients with amyotrophic lateral sclerosis

Slowing of sensory nerve conduction is an unexplained finding in patients with sporadic amyotrophic lateral sclerosis (ALS). To study the frequency of these abnormalities and to study if a predisposition to the development of entrapment neuropathies is causal, 23 patients with definite ALS and 23 age-matched healthy volunteers were investigated prospectively. Antidromic sensory and motor nerve conduction velocities (NCVs) were measured in ulnar and median nerves. Median sensory NCV was abnormally low in three patients if compared with the lower limit of the control group; and median sensory NCV was abnormally low in nine patients (six right, eight left hands) if compared with ipsilateral ulnar sensory NCV. Sensory nerve conduction data did not correlate with clinical findings, such as forearm weakness or usage of canes. Motor nerve conduction data did not correlate with sensory nerve conduction data, with the exception of distal motor latency of right median nerves, which correlated with right median sensory NCV. Our findings show how affection of sensory fibers of distal segments of median nerves can be detected in individual patients with ALS. Nerve entrapment may contribute to this affection, but it is not the only cause. This should be considered in discussions about diagnostic criteria for ALS.

Requests for electromyography from general practitioners and specialists: critical evaluation

In order to improve the quality of service and limit costs of a local electromyographic service, the requests for electromyographic (EMG) examination issued by general practitioners and specialists were critically evaluated. The diagnoses suspected by referring doctors were compared with medical history and clinical data to analyze (1) the utility of EMG for the final diagnosis and (2) the concordance with that of the neurophysiologist and with the EMG results. In 1994 and 1995, there were 3482 patients referred to the EMG service. Only patients undergoing EMG for the first time (2706 subjects) were considered. In 76.6% of cases, the referring doctor had indicated the suspected diagnosis in the request. This diagnosis was compatible with medical history, symptoms and the results of neurological examination in 57.6% of cases. In 77.2%, the neurophysiologist considered the EMG useful in confirming the clinical diagnosis. The suspected diagnosis was confirmed by the clinical diagnosis of the neurophysiologist and by the EMG results in 54.2% and 45.4% of cases, respectively. When the request was issued by neurosurgeons, neurologists, orthopedists, rheumatologists and physiatrists, the suspected diagnosis was more accurate; as a consequence the EMG was more correctly oriented than when the request was issued by other specialists or by general practitioners. It is recommended that neurological examination be a prerequisite for EMG requests issued by general practitioners.

Electrodiagnostic studies in clinical trials for motor neuron disease

Motor neuron disease (MND) is a group of neurodegenerative disorders characterized by death of upper motor neurons (UMN) and lower motor neurons (LMN). Clinical study of UMN loss is limited, but electrodiagnostic studies can be used readily to assess the functional state of LMN. Electrodiagnostic studies are regularly used in making the diagnosis of amyotrophic lateral sclerosis (ALS) and other forms of MND. They can also be used to follow disease progression and serve as end point measures in drug trials. In this role, electrodiagnostic studies can provide specific information not readily available from measurement of muscle strength or clinical functional scales. This article emphasizes the primary pathologic and secondary physiologic changes that take place after LMN loss and how they can be assessed by electrodiagnostic studies. It reviews the uses of routine electrodiagnostic studies for the diagnosis of MND but focuses on how special electrodiagnostic studies can be used as end point measures in drug trials.

Sera from amyotrophic lateral sclerosis patients reduce high-voltage activated Ca2+ currents in mice dorsal root ganglion neurons

This study investigated the effects of sera from amyotrophic lateral sclerosis (ALS) patients on high voltage activated (HVA) Ca2+ current in mice dorsal root ganglion (DRG) cells using whole-cell voltage-clamp method. Mice were injected with sera from healthy adults, from patients with other neurological diseases, and from patients with the sporadic form of ALS, for a period of 3 days. Sera from five of six ALS patients reduced HVA Ca2+ current amplitude. The peak Ca2+ current was significantly reduced by ALS sera while the sera from healthy adults and patients with other diseases did not alter Ca2+ current. The inactivation kinetics was altered by ALS sera, and the half-inactivation voltage shifted to more negative potential in ALS group. These results suggest that sporadic ALS serum factors may exert interactions with the HVA Ca2+ channel in DRG cells to reduce the Ca2+ current.

Carpal tunnel syndrome in amyotrophic lateral sclerosis and late onset cerebellar ataxia

We report on clinical and electrophysiological findings and management in nine patients who developed carpal tunnel syndrome during the course of amyotrophic lateral sclerosis and late onset cerebellar ataxia, two neurodegenerative diseases. The patients were treated with surgical decompression (five cases) and local steroid injections (four cases). Only one showed lasting relief of symptoms and significantly improved distal conduction in the median nerve at follow-up after 2 to 3 months. The symptoms and conduction data remained unchanged in three patients who could be followed for more than 1 year. We think that axonal neuropathy plays an important role in the development of carpal tunnel syndrome in these patients and accounts for the failure of the standard treatments.

Electrophysiological findings in peripheral fibres of subjects with and without post-herpetic neuralgia

The peripheral nervous system was studied using classical electrophysiological methods in 23 subjects with post-herpetic neuralgia (PHN), and compared with the same parameters in 64 herpes zoster (HZ) patients without PHN. The findings indicated sensory axonopathy, the severity of which varied in different patients. Ten percent of all cases showed segmental paresis corresponding to dermatomes affected by HZ. In another 17% of patients axonal motor damage was only detectable by EMG as denervation. No statistically significant difference was found between the two groups in the mean percentage differences of the electrophysiological data for peripheral sensory fibres with respect to mean control values, or between sides affected by HZ and healthy sides. Hence HZ is associated with sensory axonopathy, the severity of which is similar, on the whole, in the groups with and without PHN and stable in time. This suggests that damage to peripheral large-diameter sensory fibres is not the cause of PHN.

Multifocal motor neuropathy with conduction block: a study of 24 patients

Twenty four patients with pure motor neuropathy are reported. The chronic motor involvement associated with fasciculations and cramps, mainly in the arms, led, in most patients, to an initial diagnosis of motor neuron disease. In some patients (nine of 24), there was no appreciable muscle atrophy. Tendon reflexes were often absent or weak. The finding of persistent multifocal conduction block confined to motor nerve fibres raises questions about the nature and the importance of this syndrome. Segmental reduction of motor conduction velocity occurred at the site of the block, but significant slowing of motor nerve conduction was not found outside this site. The response to intravenous IVIg treatment seems to be correlated with the absence of amyotrophy. Patients with little or no amyotrophy had an initial and sustained response to IVIg, and did not develop amyotrophy during the follow up study. They could be considered to have a variant of chronic inflammatory demyelinating polyneuropathy. Patients with pronounced amyotrophy independent of the disease duration did not respond as well to IVIg treatment, suggesting the existence of a distinct entity. Among the patients treated about two thirds who had an initial good response to IVIg had high or significant antiganglioside GM1 (anti-GM1) antibody titres, but there was no correlation between the high titres before treatment and long lasting response to IVIg treatment.

Electrophysiological evidence of "nerve entrapment syndromes" and subclinical peripheral neuropathy in progressive systemic sclerosis (scleroderma)

We report the electrophysiological findings and the management of 5 subjects with progressive systemic sclerosis (PSS) and clinical evidence of nerve entrapment. Three had carpal tunnel syndrome (CTS), 1 bilateral CTS and right tarsal tunnel syndrome (TTS) and 1 Guyon's canal syndrome. Only 1 patient (with CTS) showed significant clinical improvement after surgical decompression; the other 4 demonstrated a slight recovery of conduction without lasting clinical relief after conventional treatment. To explain these failures we hypothesized that these entrapment syndromes were the clinical expression of underlying diffuse damage to the peripheral nervous system (PNS). The conduction values of nerves unaffected by entrapment syndromes were within normal limits, but almost all distal velocities were below the mean of controls. Such subclinical distal peripheral neuropathy was also verified in a selected sample of 17 patients with PSS, without clinical symptoms or signs of PNS involvement. In these 17 cases the mean distal sensory and motor conduction findings of the median, ulnar, sural and tibial nerves were significantly lower than those of a control group, while no significant differences were found in the more proximal tracts of the same nerves. Furthermore, 3 of the 17 patients showed classical electrophysiological evidence of TCS and TTS without any clinical symptoms. We conclude that the subjects with PSS had subclinical polyneuropathy which may become plain polyneuropathy or nerve entrapment syndromes perhaps induced by other risk factors.