The spectrum of lower motor neuron syndromes

Clinical and neuroanatomical characterization of the semantic behavioral variant of frontotemporal dementia in a multicenter Italian cohort

BACKGROUND

Semantic behavioral variant frontotemporal dementia (sbvFTD) is a neurodegenerative condition presenting with specific behavioral and semantic derangements and predominant atrophy of the right anterior temporal lobe (ATL). The objective was to evaluate clinical, neuropsychological, neuroimaging, and genetic features of an Italian sbvFTD cohort, defined according to recently proposed guidelines, compared to semantic variant primary progressive aphasia (svPPA) and behavioral variant FTD (bvFTD) patients.

METHODS

Fifteen sbvFTD, sixty-three bvFTD, and twenty-five svPPA patients and forty controls were enrolled. Patients underwent clinical, cognitive evaluations, and brain MRI. Symptoms of bvFTD patients between onset and first visit were retrospectively recorded and classified as early and late. Grey matter atrophy was investigated using voxel-based morphometry.

RESULTS

sbvFTD experienced early criteria-specific symptoms: world, object and person-specific semantic loss (67%), complex compulsions and rigid thought (60%). Sequentially, more behavioral symptoms emerged (apathy/inertia, loss of empathy) along with non-criteria-specific symptoms (anxiety, suspiciousness). sbvFTD showed sparing of attentive/executive functions, especially compared to bvFTD and better language functions compared to svPPA. All sbvFTD patients failed at the famous face recognition test and more than 80% failed in understanding written metaphors and humor. At MRI, sbvFTD had predominant right ATL atrophy, almost specular to svPPA. Three sbvFTD patients presented pathogenic genetic variants.

CONCLUSION

We replicated the application of sbvFTD diagnostic guidelines in an independent Italian cohort, demonstrating that the presence of person-specific semantic knowledge loss and mental rigidity, along with preserved executive functions and a predominant right ATL atrophy with sparing of frontal lobes, should prompt a diagnosis of sbvFTD.

Critical illness-associated weakness and related motor disorders

Weakness of limb and respiratory muscles that occurs in the course of critical illness has become an increasingly common and serious complication of adult and pediatric intensive care unit patients and a cause of prolonged ventilatory support, morbidity, and prolonged hospitalization. Two motor disorders that occur singly or together, namely critical illness polyneuropathy and critical illness myopathy, cause weakness of limb and of breathing muscles, making it difficult to be weaned from ventilatory support, commencing rehabilitation, and extending the length of stay in the intensive care unit, with higher rates of morbidity and mortality. Recovery can take weeks or months and in severe cases, and may be incomplete or absent. Recent findings suggest an improved prognosis of critical illness myopathy compared to polyneuropathy. Prevention and treatment are therefore very important. Its management requires an integrated team approach commencing with neurologic consultation, creatine kinase (CK) measurement, detailed electrodiagnostic, respiratory and neuroimaging studies, and potentially muscle biopsy to elucidate the etiopathogenesis of the weakness in the peripheral and/or central nervous system, for which there may be a variety of causes. These tenets of care are being applied to new cases and survivors of the coronavirus-2 disease pandemic of 2019. This chapter provides an update to the understanding and approach to critical illness motor disorders.

Spinal cord motor disorders

Spinal cord diseases are frequently devastating due to the precipitous and often permanently debilitating nature of the deficits. Spastic or flaccid paraparesis accompanied by dermatomal and myotomal signatures complementary to the incurred deficits facilitates localization of the insult within the cord. However, laboratory studies often employing disease-specific serology, neuroradiology, neurophysiology, and cerebrospinal fluid analysis aid in the etiologic diagnosis. While many spinal cord diseases are reversible and treatable, especially when recognized early, more than ever, neuroscientists are being called to investigate endogenous mechanisms of neural plasticity. This chapter is a review of the embryology, neuroanatomy, clinical localization, evaluation, and management of adult and childhood spinal cord motor disorders.

Profiling morphologic MRI features of motor neuron disease caused by TARDBP mutations

Objective

Mutations in the TARDBP gene are a rare cause of genetic motor neuron disease (MND). Morphologic MRI characteristics of MND patients carrying this mutation have been poorly described. Our objective was to investigate distinctive clinical and MRI features of a relatively large sample of MND patients carrying TARDBP mutations.

Methods

Eleven MND patients carrying a TARDBP mutation were enrolled. Eleven patients with sporadic MND (sMND) and no genetic mutations were also selected and individually matched by age, sex, clinical presentation and disease severity, along with 22 healthy controls. Patients underwent clinical and cognitive evaluations, as well as 3D T1-weighted and diffusion tensor (DT) MRI on a 3 Tesla scanner. Gray matter (GM) atrophy was first investigated at a whole-brain level using voxel-based morphometry (VBM). GM volumes and DT MRI metrics of the main white matter (WM) tracts were also obtained. Clinical, cognitive and MRI features were compared between groups.

Results

MND with TARDBP mutations was associated with all possible clinical phenotypes, including isolated upper/lower motor neuron involvement, with no predilection for bulbar or limb involvement at presentation. Greater impairment at naming tasks was found in TARDBP mutation carriers compared with sMND. VBM analysis showed significant atrophy of the right lateral parietal cortex in TARDBP patients, compared with controls. A distinctive reduction of GM volumes was found in the left precuneus and right angular gyrus of TARDBP patients compared to controls. WM microstructural damage of the corticospinal tract (CST) and inferior longitudinal fasciculi (ILF) was found in both sMND and TARDBP patients, compared with controls, although decreased fractional anisotropy of the right CST and increased axial diffusivity of the left ILF (p = 0.017) was detected only in TARDBP mutation carriers.

Conclusions

TARDBP patients showed a distinctive parietal pattern of cortical atrophy and greater damage of motor and extra-motor WM tracts compared with controls, which sMND patients matched for disease severity and clinical presentation were lacking. Our findings suggest that TDP-43 pathology due to TARDBP mutations may cause deeper morphologic alterations in both GM and WM.

Pilot Study on Quantitative Cervical Cord and Muscular MRI in Spinal Muscular Atrophy: Promising Biomarkers of Disease Evolution and Treatment?

Introduction: Nusinersen is a recent promising therapy approved for the treatment of spinal muscular atrophy (SMA), a rare disease characterized by the degeneration of alpha motor neurons (αMN) in the spinal cord (SC) leading to progressive muscle atrophy and dysfunction. Muscle and cervical SC quantitative magnetic resonance imaging (qMRI) has never been used to monitor drug treatment in SMA. The aim of this pilot study is to investigate whether qMRI can provide useful biomarkers for monitoring treatment efficacy in SMA.

Methods: Three adult SMA 3a patients under treatment with nusinersen underwent longitudinal clinical and qMRI examinations every 4 months from baseline to 21-month follow-up. The qMRI protocol aimed to quantify thigh muscle fat fraction (FF) and water-T2 (w-T2) and to characterize SC volumes and microstructure. Eleven healthy controls underwent the same SC protocol (single time point). We evaluated clinical and imaging outcomes of SMA patients longitudinally and compared SC data between groups transversally.

Results: Patient motor function was stable, with only Patient 2 showing moderate improvements. Average muscle FF was already high at baseline (50%) and progressed over time (57%). w-T2 was also slightly higher than previously published data at baseline and slightly decreased over time. Cross-sectional area of the whole SC, gray matter (GM), and ventral horns (VHs) of Patients 1 and 3 were reduced compared to controls and remained stable over time, while GM and VHs areas of Patient 2 slightly increased. We found altered diffusion and magnetization transfer parameters in SC structures of SMA patients compared to controls, thus suggesting changes in tissue microstructure and myelin content.

Conclusion: In this pilot study, we found a progression of FF in thigh muscles of SMA 3a patients during nusinersen therapy and a concurrent slight reduction of w-T2 over time. The SC qMRI analysis confirmed previous imaging and histopathological studies suggesting degeneration of αMN of the VHs, resulting in GM atrophy and demyelination. Our longitudinal data suggest that qMRI could represent a feasible technique for capturing microstructural changes induced by SMA in vivo and a candidate methodology for monitoring the effects of treatment, once replicated on a larger cohort.

The upper cervical spinal cord in ALS assessed by cross-sectional and longitudinal 3T MRI

The upper cervical spinal cord is measured in a large longitudinal amyotrophic lateral sclerosis (ALS) cohort to evaluate its role as a biomarker. Specifically, the cervical spinal cord´s cross-sectional area (CSA) in plane of the segments C1–C3 was measured semi-automatically with T1-weighted 3T MRI sequences in 158 ALS patients and 86 controls. Six-month longitudinal follow-up MRI scans were analyzed in 103 patients. Compared to controls, in ALS there was a significant mean spinal cord atrophy (63.8 mm² vs. 60.8 mm², p = 0.001) which showed a trend towards worsening over time (mean spinal cord CSA decrease from 61.4 mm² to 60.6 mm² after 6 months, p = 0.06). Findings were most pronounced in the caudal segments of the upper cervical spinal cord and in limb-onset ALS. Baseline CSA was related to the revised ALS functional rating scale, disease duration, precentral gyrus thickness and total brain gray matter volume. In conclusion, spinal cord atrophy as assessed in brain MRIs in ALS patients mirrors the extent of overall neurodegeneration and parallels disease severity.

Neurotheranostics as personalized medicines

The discipline of neurotheranostics was forged to improve diagnostic and therapeutic clinical outcomes for neurological disorders. Research was facilitated, in largest measure, by the creation of pharmacologically effective multimodal pharmaceutical formulations. Deployment of neurotheranostic agents could revolutionize staging and improve nervous system disease therapeutic outcomes. However, obstacles in formulation design, drug loading and payload delivery still remain. These will certainly be aided by multidisciplinary basic research and clinical teams with pharmacology, nanotechnology, neuroscience and pharmaceutic expertise. When successful the end results will provide "optimal" therapeutic delivery platforms. The current report reviews an extensive body of knowledge of the natural history, epidemiology, pathogenesis and therapeutics of neurologic disease with an eye on how, when and under what circumstances neurotheranostics will soon be used as personalized medicines for a broad range of neurodegenerative, neuroinflammatory and neuroinfectious diseases.

Fasciculation potentials and decremental responses in amyotrophic lateral sclerosis

OBJECTIVE

The positive correlation between fasciculation potentials (FPs) and decremental responses in repetitive nerve stimulation test (RNS) in amyotrophic lateral sclerosis (ALS) patients has been described based on only one past study. We revisited this issue.

METHODS

Subjects consisted of 30 prospectively-enrolled ALS patients on whom both needle EMG and RNS were conducted in the same trapezius muscle. Fasciculation potentials (FPs) were identified off-line from the restored 3-min signal. Firing rate of FPs (FR-FP) per minute was calculated from the total count of FPs of different origins. Correlations between FR-FP, decremental percentage (Decr%) and the amplitude of the initial compound muscle action potential (CMAPamp) in RNS were investigated.

RESULTS

There was no correlation between FR-FP and Decr% (r = 0.03) or between FR-FP and CMAPamp (r = 0.04). A significant negative correlation was observed between CMAPamp and Decr% (r = -0.56, P < .005).

CONCLUSION

FPs are not correlated with the decremental response in RNS.

SIGNIFICANCE

The underlying mechanism for FPs and decremental responses in ALS must be different and unrelated to each other.

Cervical Spinal Cord Atrophy Profile in Adult SMN1-Linked SMA

PURPOSE

The mechanisms underlying the topography of motor deficits in spinal muscular atrophy (SMA) remain unknown. We investigated the profile of spinal cord atrophy (SCA) in SMN1-linked SMA, and its correlation with the topography of muscle weakness.

MATERIALS AND METHODS

Eighteen SMN1-linked SMA patients type III/V and 18 age/gender-matched healthy volunteers were included. Patients were scored on manual muscle testing and functional scales. Spinal cord was imaged using 3T MRI system. Radial distance (RD) and cord cross-sectional area (CSA) measurements in SMA patients were compared to those in controls and correlated with strength and disability scores.

RESULTS

CSA measurements revealed a significant cord atrophy gradient mainly located between C3 and C6 vertebral levels with a SCA rate ranging from 5.4% to 23% in SMA patients compared to controls. RD was significantly lower in SMA patients compared to controls in the anterior-posterior direction with a maximum along C4 and C5 vertebral levels (p-values < 10-5). There were no correlations between atrophy measurements, strength and disability scores.

CONCLUSIONS

Spinal cord atrophy in adult SMN1-linked SMA predominates in the segments innervating the proximal muscles. Additional factors such as neuromuscular junction or intrinsic skeletal muscle defects may play a role in more complex mechanisms underlying weakness in these patients.

Acupuncture plus low-frequency electrical stimulation (Acu-LFES) attenuates denervation-induced muscle atrophy

Muscle wasting occurs in a variety of clinical situations, including denervation. There is no effective pharmacological treatment for muscle wasting. In this study, we used a tibial nerve denervation model to test acupuncture plus low-frequency electric stimulation (Acu-LFES) as a therapeutic strategy for muscle atrophy. Acupuncture needles were connected to an SDZ-II electronic acupuncture device delivering pulses at 20 Hz and 1 mA; the treatment was 15 min daily for 2 wk. Acu-LFES prevented soleus and plantaris muscle weight loss and increased muscle cross-sectional area in denervated mice. The abundances of Pax7, MyoD, myogenin, and embryonic myosin heavy chain were significantly increased by Acu-LFES in both normal and denervated muscle. The number of central nuclei was increased in Acu-LFES-treated muscle fibers. Phosphorylation of Akt was downregulated by denervation leading to a decline in muscle mass; however, Acu-LFES prevented the denervation-induced decline largely by upregulation of the IGF-1 signaling pathway. Acu-LFES reduced the abundance of muscle catabolic proteins forkhead O transcription factor and myostatin, contributing to the attenuated muscle atrophy. Acu-LFES stimulated the expression of macrophage markers (F4/80, IL-1b, and arginase-1) and inflammatory cytokines (IL-6, IFNγ, and TNFα) in normal and denervated muscle. Acu-LFES also stimulated production of the muscle-specific microRNAs miR-1 and miR-206. We conclude that Acu-LFES is effective in counteracting denervation-induced skeletal muscle atrophy and increasing muscle regeneration. Upregulation of IGF-1, downregulation of myostatin, and alteration of microRNAs contribute to the attenuation of muscle atrophy in denervated mice.

Sporadic lower motor neuron disease with a snake eyes appearance on the cervical anterior horns by MRI

OBJECTIVE

Lower motor neuron disease (LMND) is the term generally used to describe diseases in which only lower motor neuron signs are detected. A snake eyes appearance on magnetic resonance imaging (MRI) is associated with a wide spectrum of neurological conditions including LMND. The author reports on three unique LMND patients with upper limb muscle weakness and atrophy who show a snake eyes appearance by MRI.

PATIENTS AND METHODS

The patients were aged 18, 40 and 52 years, respectively, at the onset of the disease and had a longstanding clinical course (more than 10 years for two patients and 8 years for one patient). They were followed up for more than 6 years.

RESULTS

Clinical manifestations were characterized by (1) longstanding slow progression or delayed spontaneous arrest of asymmetric lower motor neuron signs localized exclusively in the upper extremities with unilateral predominance and distal or proximal preponderance; (2) the absence of upper motor neuron signs, bulbar signs, sensory disturbances and respiratory involvement; (3) a snake eyes appearance on the anterior horns of the cervical cord over more than 3 vertebrae by axial T2-weighted MRI and a longitudinal linear-shaped T2-signal hyperintensity by sagittal MRI; (4) neurogenic change with fasciculation and denervation potentials (fibrillation and a positive sharp wave) confined to the affected muscles by needle electromyogram; and (5) normal cerebrospinal fluid and a normal creatine kinase level. These cases did not fall into any existing category of LMND, such as progressive muscular atrophy, flail arm syndrome or Hirayama disease.

CONCLUSIONS

These patients should be classified as sporadic LMND with snake eyes on MRI with a relatively benign prognosis.

Peripheral nerve ultrasound in amyotrophic lateral sclerosis phenotypes

INTRODUCTION

In this study we sought to determine the cross-sectional area (CSA) of peripheral nerves in patients with distinct subtypes of amyotrophic lateral sclerosis (ALS).

METHODS

Ulnar and median nerve ultrasound was performed in 78 ALS patients [classic, n = 21; upper motor neuron dominant (UMND), n = 14; lower motor neuron dominant (LMND), n = 20; bulbar, n = 15; primary lateral sclerosis (PLS), n = 8] and 18 matched healthy controls.

RESULTS

Compared with controls, ALS patients had significant, distally pronounced reductions of ulnar CSA (forearm/wrist level) across all disease groups, except for PLS. Median nerve CSA (forearm/wrist level) did not differ between controls and ALS.

CONCLUSION

Ulnar nerve ultrasound in ALS subgroups revealed significant differences in distal CSA values, which suggests it has value as a marker of LMN involvement. Its potential was particularly evident in the UMND and PLS groups, which can be hard to separate clinically, yet their accurate separation has major prognostic implications.

Practical rules for electrodiagnosis in suspected multifocal motor neuropathy

Multifocal motor neuropathy (MMN) with conduction block (CB) is a rare chronic immune-mediated neuropathy, but important to diagnose as it is treatable. The key features in prototypic MMN are electrodiagnostic demonstration of focal CB away from common sites of entrapment and normal sensory conduction across these sites. However, there are challenges in distinguishing CB from the effects of abnormal temporal dispersion. Consensus electrodiagnostic criteria, reinforced by modeling studies, are available to support definite or probable CB. In addition, consideration of technical issues can guard against false-positive and false-negative conclusions. These include limb temperature, stimulus site, inadvertent stimulating electrode movement, and supramaximal and submaximal responses, as well as the possibility of Martin-Gruber anastamosis. Robust evidence supports the treatment of MMN with intravenous immunoglobulin, and guidelines have been developed. Application of practical and simple rules including a 4-step diagnostic algorithm can help practitioners correctly diagnose this treatable condition and improve patient outcomes.

The clinical spectrum of isolated peripheral motor dysfunction

INTRODUCTION

Isolated peripheral motor dysfunction due to lower motor neuron or peripheral nerve disorders presents an interesting challenge to clinicians because of the diverse differential diagnosis with a broad range of prognoses.

METHODS

We retrospectively reviewed clinical data of adults who presented over 12 years with muscle weakness, atrophy, or fasciculations, but without hyperreflexia or sensory involvement.

RESULTS

In 119 patients, 52% had a motor neuron disease (MND), 13% had immune neuropathies, 11% had genetic neuronopathies, 10% had residual or post-polio syndrome, 5% had benign fasciculation, 1% had an infectious etiology, and 8% were not given a final diagnosis. Only MND patients had cognitive dysfunction or frontal release signs. Bulbar and respiratory symptoms virtually excluded consideration of immune neuropathy.

CONCLUSIONS

Only half of the patients were diagnosed with MND. A significant minority have treatable conditions. Cognitive involvement, frontal release signs, and bulbar or respiratory symptoms are strongly suggestive of MND.

New insight into neurodegeneration: the role of proteomics

Recent advances within the field of proteomics, including both upstream and downstream protocols, have fuelled a transition from simple protein identification to functional analysis. A battery of proteomics approaches is now being employed for the analysis of protein expression levels, the monitoring of cellular activities and for gaining an increased understanding into biochemical pathways. Combined, these approaches are changing the way we study disease by allowing accurate and targeted, large scale protein analysis, which will provide invaluable insight into disease pathogenesis. Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), prion disease, and other diseases that affect the neuromuscular system, are a leading cause of disability in the aging population. There are no effective intervention strategies for these disorders and diagnosis is challenging as it relies primarily on clinical symptomatic features, which often overlap at early stages of disease. There is, therefore, an urgent need to develop reliable biomarkers to improve early and specific diagnosis, to track disease progression, to measure molecular responses towards treatment regimes and ultimately devise new therapeutic strategies. To accomplish this, a better understanding of disease mechanisms is needed. In this review we summarize recent advances in the field of proteomics applicable to neurodegenerative disorders, and how these advances are fueling our understanding, diagnosis, and treatment of these complex disorders.

A Classificacao Internacional de Doencas, a Familia de Classificacoes Internacionais, a CID-11 e a Sindrome Pos-Poliomielite

The first International Classification of Diseases (ICD) was approved in 1893 and since then it has been periodically reviewed. The last, 10th revision (ICD-10), was approved in 1989. Since 1989, it was possible to update from ICD revisions, which did not happen before. The next revision (ICD-11) would probably be published in 2015. In 1989, mechanisms were established to update ICD-10, through the creation of the Morbidity Reference Group (MbRG) in 1997 and the Update and Revision Committee (URC) in 2000. The Morbidity Reference Group (MbRG) was created in 2007 to discuss in more detail the issues to update morbidity. A specific code in ICD was not included in the revision of ICD-10 in 1989 for the post-polio syndrome (PPS). However, the ICD new code G14 for PPS was included in ICD-10 since 2010.

Homozygous survival motor neuron 2 gene deletion and sporadic lower motor neuron disease in children: case report and literature review

A case of lower motor neuron disease with homozygous survival motor neuron 2 (SMN2) gene deletion is reported in this article. A 7-year-old boy was admitted to our hospital with main complaints of lower extremity weakness and difficulty squatting for the past year. SMN gene copies were quantified by multiplex ligation-dependent probe amplification. Exons 7 and 8 of the SMN1 gene were normal, but homozygous deletion of exons 7 and 8 of the SMN2 gene was identified. Homozygous deletion of exons 7 and 8 of the SMN centromeric gene was detected, and exons 7 and 8 of the SMN1 gene were found to be normal in the proband. Two copies of exons 7 and 8 of the SMN1 gene were identified, and zero copies of exons 7 and 8 of the SMN2 gene were found. We consider that this case represents a previously unrecognized type of lower motor neuron disease that resulted from homozygous deletion of the SMN2 gene.

Arthrogryposis and fetal hypomobility syndrome

Arthrogryposis is a heterogeneous condition, evident from birth, which can be defined as multiple contractures of the joints. The etiology is multifold: genetic disorders of the central or peripheral nervous system, or of the connective tissue leading to decreased fetal movements, and vascular and environmental causes. The problem begins in utero. There may be overlapping conditions between sporadic, syndromic, neurogenic, myopathic and metabolic types. The workup should include a family tree. Systemic involvement, for example of the renal and pulmonary systems, may be encountered in associated syndromes. Motor neuron disorders leading to the condition are the most commonly seen type. Fetal or neonatal akinesia/hypokinesia is at the severe end of the spectrum, in which there is literally intrauterine limitation of movement. Children with amyplasia are born with little or diminished muscle bulk of the extremities. Distal arthrogryposis is almost always a dominantly inherited condition. A multidisciplinary care approach is required in order to provide optimum healthcare. The management team should include a nutritionist and a physiotherapist. Genetic counseling is possible in most instances. A truly genetic cause can be identified in more than 50% of cases. Survivors, though handicapped, can lead near normal lives.

Neuromuscular complications

Although direct neoplastic involvement of muscle tis-sue is surprisingly rare, considering the large amount of body mass that is represented by muscle tissue, the most important and unresolved muscle effect is muscle cachexia.Other associations, such as inflammatory, paraneo-plastic, toxic, and several extremely rare associations,have been described. Drug-induced toxicity and radiation recall syndrome need to be taken into consideration when muscle symptoms appear in patients with cancer.

Predicting a positive response to intravenous immunoglobulin in isolated lower motor neuron syndromes

OBJECTIVE

To determine clinically related characteristics in patients with pure lower motor neuron (LMN) syndromes, not fulfilling accepted diagnostic criteria, who were likely to respond to intravenous immunoglobulin (IVIg) treatment.

METHODS

Demographic, clinical, laboratory and neurophysiological characteristics were prospectively collected from patients with undifferentiated isolated LMN syndromes who were then treated with IVIg. Patients were classified as either responders or non-responders to therapy with IVIg based on clinical data and the two groups were compared.

RESULTS

From a total cohort of 42 patients (30 males, 12 females, aged 18-83 years), 31 patients responded to IVIg and 11 did not. Compared to patients that developed progressive neurological decline, responders were typically younger (45.8 compared to 56.0 years, P<0.05) and had upper limb (83.9% compared to 63.6%, NS), unilateral (80.6% compared to 45.5%, P<0.05), and isolated distal (54.1% compared to 9.1%, P<0.05) weakness. Patients with predominantly upper limb, asymmetrical, and distal weakness were more likely to respond to IVIg therapy. Of the patients who responded to treatment, only 12.9% had detectable GM(1) antibodies and conduction block (not fulfilling diagnostic criteria) was only identified in 22.6%.

CONCLUSIONS

More than 70% of patients with pure LMN syndromes from the present series responded to treatment with IVIg therapy, despite a low prevalence of detectable GM(1) antibodies and conduction block. Patients with isolated LMN presentations, not fulfilling accepted diagnostic criteria, may respond to IVIg therapy, irrespective of the presence of conduction block or GM(1) antibodies, and should be given an empirical trial of IVIg to determine treatment responsiveness.

Do A-waves help predict intravenous immunoglobulin response in multifocal motor neuropathy without block?

INTRODUCTION

Are there electrophysiological findings that predict response to intravenous immunoglobulin (IVIg) in patients with lower motor neuron (LMN) syndromes without multifocal conduction block (MCB)?

METHODS

We enrolled 9 patients with LMN syndromes without MCB to receive 18 weeks of IVIg therapy. Response was measured at weeks 2 and 18 using the Appel Amyotrophic Lateral Sclerosis (AALS) score (includes grip and pincer strength measures), ALS Functional Rating Scale (ALSFRS), and electrophysiological measures, including motor unit estimates (MUNEs).

RESULTS

No change occurred in AALS or ALSFRS scores posttreatment. Grip/pincer strength increased in 7 patients (P = 0.028) after initial treatment (responders); 2 showed no improvement (non-responders). No electrophysiological measure changed after treatment in either group but MUNEs trended higher (P = 0.055). "Abnormal A-waves" (complex, repetitive biphasic, or present in multiple nerves) occurred in pretreatment studies more often in responders (P = 0.028).

DISCUSSION

"Abnormal A-waves" may signal IVIg-responsive LMN syndromes even if conduction block is absent.

Clinical patterns in progressive muscular atrophy (PMA): A prospective study

Progressive muscular atrophy (PMA) is a form of motor neuron disease, but its outcome is not well defined, and the aim was to study the pattern of clinical progression in PMA. We studied 10 patients prospectively for 12 months. None showed clinical signs of upper motor neuron involvement at presentation or during follow-up, and all had normal transcranial magnetic stimulation studies. Four had upper limb onset, four lower limb onset and two axial onset. We used neurophysiological and strength measurements and a clinical rating scale (ALS-FRS). Seven other patients presenting with a PMA syndrome developed upper motor neuron signs during a one-year period of observation and were excluded from the study. The rate of progression was variable. At six months, only motor unit number estimation (MUNE) and ALS-FRS had decreased significantly. The Neurophysiological Index (NI) and M-wave amplitude measurements decreased at 12 months. Two patients with axial-onset disease progressed rapidly to respiratory failure. Overall the pattern of change resembled that of ALS, although some patients progressed very slowly. Axial onset, however, predicts the early onset of respiratory failure, and a poor prognosis.

Cranial nerves palsy as an initial feature of an early onset distal hereditary motor neuropathy--a new distal hereditary motor neuropathy phenotype

Distal hereditary motor neuropathy is a heterogeneous group of disorders characterised by a pure motor axonal neuropathy. It is occasionally associated with additional signs such as facial weakness, vocal cord paralysis, weakness of the diaphragm, and pyramidal signs. Although predominantly the inheritance is autosomal dominant, all types of inheritance have been described. Here we report a Czech family with cranial nerves palsy as an initial feature of a non progressive infantile onset dominant distal hereditary motor neuropathy. This family may represent a new subtype of distal hereditary motor neuropathy.

[Progressive muscle atrophy. A rarely diagnosed variant of amyotrophic lateral sclerosis]

Progressive muscle atrophy (PMA) is a degenerative disease of the lower motor neuron. The course of the illness and the fatal prognosis correspond to those of amyotrophic lateral sclerosis (ALS). Neuropathologic and genetic findings support categorizing PMA within the spectrum of ALS, even though no clinical sign of a disorder of the upper motor neuron is demonstrable. The diagnosis of PMA is based on advanced extremity pareses and atrophies with a high progression rate. Respiratory insufficiency is determinative of the prognosis. Absent or late affection of bulbar functions is characteristic of the disease. Intraneuronal bunina bodies and ubiquitine-positive inclusions, which are established morphologic characteristics of ALS, are found post mortem. The treatment options of riluzol medication, respiratory therapy, and nutrition are analogous to those for typical ALS.

Progressive muscle atrophy with hypokalemic periodic paralysis and calcium channel mutation

A family with hypokalemic periodic paralysis (HypoPP) and motor neuron degeneration is reported. In conjunction with HypoPP, the index patient developed progressive muscle atrophy. The calcium channel gene CACNA1S showed a mutation encoding p.R528H, which has been related previously to HypoPP. We propose that CACNA1S mutations may comprise a previously unrecognized genetic risk factor in a greater spectrum of motor unit disorders including amyotrophic lateral sclerosis.

Investigation of the role of SMN1 and SMN2 haploinsufficiency as a risk factor for Hirayama's disease: Clinical, neurophysiological and genetic characteristics in a Spanish series of 13 patients

OBJECTIVE

The effect of the number of copies in the SMN1 and SMN2 genes - the most extensively studied susceptibility and modifying genetic factors in adult onset motor neuron diseases - as a genetic risk factor for Hirayama's disease (HirD) has never been studied. The purpose of this study was to investigate the influence of the number of copies of the SMN1/SMN2 genes on the resulting phenotype in 13 HirD Spanish patients.

PATIENTS AND METHODS

We performed a qualitative and quantitative SMN1/SMN2 gene analysis in 13 unrelated HirD patients. The phenotype-genotype correlation was investigated, paying particular attention to the effect of the SMN1/SMN2 copy number on the disease's phenotype.

RESULTS

No patient had a homozygous deletion of the SMN1 or SMN2. No differences were found when comparing the SMN1 and SMN2 copy number distributions of the healthy population and HirD patients, and they do not therefore appear to be a susceptibility factor. There was also no correlation found between the number of copies of the SMN1 and SMN2 and the severity of the resulting phenotype.

CONCLUSION

Our results suggest that SMN1 and SMN2 are not predisposing factors for HirD and therefore support a lack of association between these genes and the resulting phenotype.

Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is an immune-mediated disorder characterised by slowly progressive, asymmetrical weakness of limbs without sensory loss. The clinical presentation of MMN mimics that of lower-motor-neuron disease, but in nerve-conduction studies of patients with MMN motor-conduction block has been found. By contrast with chronic inflammatory demyelinating polyneuropathy, treatment with prednisolone and plasma exchange is generally ineffective in MMN and even associated with clinical worsening in some patients. Of the immunosuppressants, cyclophosphamide has been reported as effective but only anecdotally. Various open trials and four placebo-controlled trials have shown that treatment with high-dose intravenous immunoglobulin leads to improvement of muscle strength in patients with MMN. Although clinical, pathological, imaging, immunological, and electrophysiological studies have improved our understanding of MMN over the past 15 years, further research is needed to elucidate pathogenetic disease mechanisms in the disorder.