Motoneuron-specific NR3B gene: no association with ALS and evidence for a common null allele

OBJECTIVE

The GRIN3B gene encodes NR3B, a motoneuron-specific member of the NMDA type of ionotropic glutamate receptors. NR3B reduces the Ca(2+)-permeability as well as the overall current of the receptor response and may thereby protect motoneurons against glutamate-mediated excitotoxicity. We tested whether genetic dysfunction of GRIN3B is implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS).

METHODS

We searched for mutations in the GRIN3B coding region (3.1 kb) in 117 individuals with familial ALS and in 46 individuals with sporadic ALS. We genotyped the newly identified GRIN3B null allele and four "tag single nucleotide polymorphisms (SNPs)" at the GRIN3B locus in 342 individuals with sporadic ALS and in 374 matched controls. The GRIN3B null allele frequency was determined in 2,128 individuals from a worldwide panel of 42 populations. We furthermore compared the GRIN3B coding sequence in primates (human-macaque) and rodents (rat-mouse) to evaluate the molecular evolution of GRIN3B.

RESULTS

Thirty-two SNPs, including 16 previously unreported SNPs, one 27-bp deletion, a polymorphic CAG repeat, and a 4-bp insertion (insCGTT), were identified. Mutational and case-control studies did not reveal variants that cause or modify disease in ALS. Intriguing is an insCGTT variant that truncates the protein at its amino terminus and results in a GRIN3B null allele. We demonstrated a global distribution of the null allele with allele frequencies ranging between 0 and 0.38, and we delineated a null allele specific haplotype of 9.89 kb. Comparative genomic analysis across four taxa demonstrated accelerated evolution of NR3B in primates.

CONCLUSIONS

Our study supports the conclusions that 1) GRIN3B does not seem to be associated with familial or sporadic ALS, 2) the GRIN3B null allele is a common polymorphism, 3) the GRIN3B null allele has arisen once and early in human evolution, and 4) the GRIN3B gene belongs to a group of nervous system-related genes that have been subjected to faster evolution during evolution.

Progressive apraxia of speech as a sign of motor neuron disease

PURPOSE

To document and describe in detail the occurrence of apraxia of speech (AOS) in a group of individuals with a diagnosis of motor neuron disease (MND).

METHOD

Seven individuals with MND and AOS were identified from among 80 patients with a variety of neurodegenerative diseases and AOS (J. R. Duffy, 2006). The history, presenting complaints, neurological findings, and speech-language findings were documented for each case.

RESULTS

Spastic or mixed spastic-flaccid dysarthria was present in all 7 cases. The AOS was judged as worse than the dysarthria in 4 cases. Nonverbal oral apraxia was eventually present in all cases. Aphasia was present in 2 cases and equivocally present in another 2. Dementia was present in 1 case and equivocally present in 2.

CONCLUSIONS

AOS can occur in MND, typically also with dysarthria, but not invariably with aphasia or other cognitive deficits. Thus, a diagnosis of MND does not preclude the presence of AOS. More importantly, MND should be a diagnostic consideration when AOS is a prominent sign of degenerative disease.

Monomelic neurogenic syndromes: a prospective study

Monomelic neurogenic syndromes are rare. Their classification and prognostic features have not been addressed in the European population. A prospective study of 17 patients with monomelic neurogenic amyotrophy, of upper or lower limb onset, with progression limited to one limb for three or more years. Clinical and neurophysiological studies were performed in the subsequent 3 or more years. Fifteen patients were of European origin and two were Asian. Those presenting with proximal monomelic weakness or with involvement of the posterior compartment of the lower leg showed no further progression after the initial period of development of the syndrome. Brisk reflexes in wasted muscles did not predict progression. Electromyographic signs of denervation in the opposite limb at presentation did not predict later progression. Transcranial magnetic stimulation (TMS) features of corticospinal dysfunction were a useful predictor of subsequent progression (p=0.01). One patient with lower limb onset developed conduction block with weakness in an upper limb nine years after presentation, and this upper limb weakness responded to IVIg therapy. This adult-onset European group of patients is different as compared with juvenile-onset Asian cases. The clinical syndromes appear heterogeneous, but neurophysiological investigations, in particular TMS, can be helpful in determining prognosis. Multifocal motor neuropathy should be considered when there is progression, even years after onset.

TDP-43 proteinopathy: the neuropathology underlying major forms of sporadic and familial frontotemporal lobar degeneration and motor neuron disease

The rapid confirmation of the initial report by Neumann et al. (Science 314:130-133, 2006) that transactive response (TAR)-DNA-binding protein 43 (TDP-43) is the major disease protein linking frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) with and without motor neuron disease (MND) as well as amyotrophic lateral sclerosis (ALS) implies that TDP-43 proteinopathy underlies major forms of sporadic as well as familial FTLD and ALS. Not only was the identity of the ubiquitinated proteins that accumulate in neurons and glia of these disorders finally resolved, but it also was shown that pathologic TDP-43 was hyperphosphorylated, ubiquitinated and cleaved to generate C-terminal fragments in affected brain and spinal cord of FTLD-U and ALS. This review summarizes the growing evidence that TDP-43 proteinopathy is the common pathologic substrate linking FTLD and ALS, and it considers the implications of these findings for developing better strategies to diagnose and treat these neurodegenerative disorders.

TDP-43 in differential diagnosis of motor neuron disorders

Motor neuron disorders are clinically and pathologically heterogeneous. They can be classified into those that affect primarily upper motor neurons, lower motor neurons or both. The most common disorder to affect both upper and lower motor neurons is amyotrophic lateral sclerosis (ALS). Some forms of motor neuron disease (MND) affect primarily motor neurons in the spinal cord or brainstem, while others affect motor neurons at all levels of the neuraxis. A number of genetic loci have been identified for the various motor neuron disorders. Several of the MND genes encode for proteins important for cytoskeletal stability and axoplasmic transport. Despite these genetic advances, the relationship of the various motor neuron disorders to each other is unclear. Except for rare familial forms of ALS associated with mutations in superoxide dismutase type 1 (SOD1), which are associated with neuronal inclusions that contain SOD1, specific molecular or cellular markers that differentiate ALS from other motor neuron disorders have not been available. Recently, the TAR DNA binding protein 43 (TDP-43) has been shown to be present in neuronal inclusions in ALS, and it has been suggested that TDP-43 may be a specific marker for ALS. This pilot study aimed to determine the value of TDP-43 in the differential diagnosis of MND. Immunohistochemistry for TDP-43 was used to detect neuronal inclusions in the medulla of disorders affecting upper motor neurons, lower motor neurons or both. Medullary motor neuron pathology also was assessed in frontotemporal lobar degeneration (FTLD) that had no evidence of MND. TDP-43 immunoreactivity was detected in the hypoglossal nucleus in all cases of ALS, all cases of FTLD-MND and some of cases of primary lateral sclerosis (PLS). It was not detected in FTLD-PLS. Surprisingly, sparse TDP-43 immunoreactivity was detected in motor neurons in about 10% of FTLD that did not have clinical or pathologic features of MND. The results suggest that TDP-43 immunoreactivity is useful in differentiating FTLD-MND and ALS from other disorders associated with upper or lower motor neuron pathology. It also reveals subclinical MND in a subset of cases of FTLD without clinical or pathologic evidence of MND.

[Pronostic factors and survival in motor neuron disease]

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is the most common adult motor neuron disease (MND), presenting with a combination of upper (UMN) and lower (lmn) motor neuron signs, with high mortality. other less frequent mnd are progressive muscular atrophy (pma) and primary lateral sclerosis (pls).

OBJECTIVES

To describe demographic data, clinical forms of presentation and evolution of patients with MND, looking for prognostic indicators factors.

METHODS

Retrospective study of a series of patients with MND, registering demographic data, clinical variables and mortality-survival, analyzed by means of statistical package SPSS 6.1.2.

RESULTS

They are 54 patients with MND (50 ALS, 3 PMA and 1 PLS), 30 (55.6%) men and 24 (44.4%) women, bulbar beginning forms in 13 cases (24.1%) and spinal in 41 (75.9%). Average age at beginning 60+/-14 (29-82 years), more delayed in women (p<0.05), and in patients with bulbar form (p<0.05) with clear predominance of female sex (p<0.03). There are 31 dead patients (57.4%) and 23 alive ones (42.6%), with average survival from the beginning symptoms of 46.51+/-40.9 months. Nine months (11-209), observing inversely proportional relation with the age of beginning of the disease (p<0.02). Bulbar beginning forms (p<0.01) and LMN affectation signs, specially bulbar and cervical levels (p<0,005), are associated with a greater probability of dying while the existence of UMN affectation signs on imaging techniques 362 ques has a greater probability of survival (p<0,05).

CONCLUSIONS

The advanced age and the bulbar beginning forms are factors of bad prognosis, specially the predominant affectation of LMN over UMN.

Celiac disease presenting with motor neuropathy: effect of gluten free-diet

Celiac disease is a rare cause of neuropathy that most commonly presents with symmetric distal sensory disturbances. We describe two patients with celiac disease in whom neuropathy presented unusually with progressive weakness of the limbs. In both patients a gluten-free diet induced a significant improvement of muscle strength and neurophysiological abnormalities, suggesting a direct pathogenetic role of sensitivity to gluten. Celiac disease should be considered in patients with idiopathic neuropathy even when gastrointestinal symptoms are absent.

Vasculitic neuropathy--electrodiagnostic findings and association with malignancies

BACKGROUND

Vasculitic neuropathies occur in the context of systemic disorders or in isolation. Histopathologic evaluation remains the gold standard for diagnosis, but certain electrodiagnostic findings may heighten suspicion of vasculitic neuropathy and improve the yield of nerve and muscle biopsy.

AIM OF THE STUDY

Description of electrodiagnostic patterns associated with vasculitic neuropathies, and a report of a possible association with malignancies.

METHODS

Retrospective review of medical records of patients with histopathologically proven vasculitic and non-vasculitic axonal neuropathies evaluated at the University of Pittsburgh Medical Center from November 1995 to November 2003.

RESULTS

The most distinctive electrodiagnostic patterns associated with vasculitic neuropathy were mononeuritis multiplex (27.5% vs 4% in controls; P = 0.003) and axonal sensorimotor polyneuropathy with side-to-side amplitude asymmetry (50% vs 32%, P > 0.05). Additionally, six patients (15% vs 2%; P = 0.034) developed various malignancies within 2 years of onset of vasculitic neuropathy.

CONCLUSIONS

While generalized polyneuropathy was the most common presentation of nerve vasculitis, our study affirms side-to-side amplitude asymmetry and mononeuritis multiplex as the most distinctive electrodiagnostic features. The frequent occurrence of malignancies suggests a possible association with the vasculitic neuropathy and warrants additional investigation.

[Mills' syndrome: a rare clinical entity]

INTRODUCTION

Mills' syndrome is a rare motor neuron disease, initially described by Mills in 1900 as a progressive ascending or descending hemiplegia without significant sensory involvement. This syndrome is of uncertain nosological status, and is supposedly due to unilateral primary degeneration of corticospinal pathway. Some authors have suggested that it could represent a variant of primary lateral sclerosis.

METHODS

We retrospectively studied the clinical and paraclinical data from eight patients with suspected Mills' syndrome hospitalized for diagnosis.

RESULTS

For all patients, the clinical course was slowly progressive, with motor deficiency, unilateral pyramidal signs (or bilateral with asymmetry), without bulbar signs, fasciculations or sensory deficit. Final diagnosis was Mills' syndrome (n=3), primary lateral sclerosis (n=1), myelitis of unknown origin (n=2), progressive primary multiple sclerosis (n=1), and antiphospholipid syndrome (n=1). The main arguments for final diagnosis were brought by electrophysiology and brain and spinal MRI.

CONCLUSION

Mills' syndrome is a rare clinical diagnosis, requiring exhaustive investigations.

Motor neuron disease associated with copper deficiency

Copper deficiency in humans is a rare cause of myeloneuropathy that usually presents with a spastic ataxic gait, hyperreflexia, and distal sensory loss similar to that seen in patients with subacute combined degeneration. We describe three copper-deficient patients, two of whom were referred with a presumptive diagnosis of amyotrophic lateral sclerosis, who had progressive asymmetric weakness or electrodiagnostic findings of proximal and distal denervation suggestive of lower motor neuron disease. Copper replacement resulted in stabilization or mild improvement in weakness. The clinical spectrum of human copper deficiency should include lower motor neuron disease in addition to a syndrome of spastic ataxia.

[Clinico-pathological investigation of two patients with dementia with motor neuron disease]

Dementia with motor neuron disease (D-MND) is characterized clinically by frontal and neurological signs, and pathologically by localized atrophy of the fronto-temporal lobes and neuronal ubiquitin(Ub)-positive inclusions. In this study, we compared the clinico-pathological findings of two patients with D-MND. Case 1 (55-year-old male): At the age of 51, he developed personality change and disinhibition, lacking neurological signs. Brain MRI exhibited localized atrophy of the frontal lobes. At the age of 54, he showed dysphagia and died after a disease duration of 4 years. Neuropathologically, the cerebrum showed localized atrophy of the dorsal area of the frontal lobes. The atrophied cerebral cortex demonstrated moderate neuronal loss with spongy change and gliosis in the superficial layers. The brainstem and spinal cord revealed moderate neuronal loss in the substantia nigra, severe neuronal loss with Bunina bodies in the hypoglossal nucleus, and moderate neuronal loss in the cervical anterior horn. There were some Ub-positive neuronal inclusions in the atrophied cortex and many in the dentate gyrus. Case 2 (68-year-old female): At the age of 64, she developed personality change, and then gait disturbance and dysarthria. Brain MRI exhibited localized atrophy of the fronto-temporal lobes. At the age of 67, she showed dysphagia with Babinski signs and died after a disease duration of 4 years. Neuropathologically, the cerebrum showed localized atrophy of the basal area of the temporal lobes, especially on the right side. The atrophied cerebral cortex demonstrated moderated neuronal loss with spongy change and gliosis in the superficial layers. The pre-central cortex revealed severe loss of Betz cells. The brainstem and spinal cord showed mild neuronal loss without Bunina bodies in the hypoglossal nucleus and cervical anterior horn, accompanied by severe degeneration of the bilateral pyramidal tracts. There were many Ub-positive neuronal inclusions with a few neurites in the atrophied cortex and some in the dentate gyrus. Cases 1 and 2 were clinically diagnosed as Pick's disease (PiD) and D-MND, respectively, although pathological diagnoses were both D-MND. Case 1 showed neuropathological findings typical to D-MND, whereas case 2 showed neuropathological findings common to atypical Pick's disease (aPiD). D-MND and aPiD are should be clinico-pathologically differentiated, although they are included in the frontotemporal lobar degeneration with motor neuron disease-type inclusions.

F-waves--physiology and clinical uses

F-waves are low amplitude responses produced by antidromic activation of motoneurons. They may not appear after each stimulus and are inherently variable in latency, amplitude, and configuration. Meaningful analysis of F-waves requires an appreciation of these characteristics of F-waves as well as an understanding of their physiology. These features of F-waves as well as their physiology are reviewed. This is important since F-waves are one of the most frequently used studies in clinical neurophysiology and much of the controversies surrounding the use of F-waves relates to a failure to adequately consider the requirements of F-wave analysis. These requirements include the number of F-waves that need to be recorded, the parameters that should be evaluated, and the muscle from which the F-waves are recorded. If analyzed correctly, current reports would indicate that F-waves are the most sensitive and reliable nerve conduction study for evaluating polyneuropathies, can be abnormal in focal proximal nerve dysfunction, can be at least as sensitive as needle electromyography for defining lumbosacral radiculopathies, and can provide a meaningful physiological window into disorders of the central nervous system. Reports supporting these statements and their clinical relevance are discussed.

Differentiation Between Primary Lateral Sclerosis and Amyotrophic Lateral Sclerosis

BACKGROUND

Motor neuron diseases can affect the upper motor neuron and/or the lower motor neuron. Both amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS) are motor neuron diseases, and there is much debate as to whether these are 2 separate disorders or simply 2 points on a continuum.

OBJECTIVE

To determine which clinical features at onset and during follow-up could help differentiate between PLS and ALS.

DESIGN

Retrospective study comparing patients with a diagnosis of PLS or ALS for differences in symptoms or signs at disease onset and during follow-up.

SETTING

Tertiary referral center. Patients Six hundred sixty-one patients with ALS and 43 patients with PLS were included in the study.

RESULTS

At presentation, stiffness was the only symptom that was significantly different between patients with PLS and patients with ALS (observed in 47% and 4% of patients, respectively; P<.001). During follow-up, limb wasting was rare in patients with PLS (2%, compared with 100% in patients with ALS; P<.001). Disease duration was significantly longer in patients with PLS compared with patients with ALS (mean +/- SD, 11.2 +/- 6.1 vs 3.8 +/- 4.2 years, respectively; P<.001). During the 16 years of follow-up, the mortality rate was significantly lower in patients with PLS compared with patients with ALS (only 33% vs 89%, respectively; P<.001).

CONCLUSION

Our findings suggest that a patient presenting with spasticity who does not develop wasting within 3 years most likely has PLS.

The value of interictal diffusion-weighted imaging in lateralizing temporal lobe epilepsy

BACKGROUND

A subgroup of patients with nonlesional temporal lobe epilepsy (TLE) has no evidence of hippocampal sclerosis on standard temporal lobe protocol MRI.

OBJECTIVE

To investigate whether interictal diffusion-weighted imaging adds lateralizing information in patients with TLE with and without lateralizing conventional MRI.

METHODS

We studied 22 patients (9 right, 13 left TLE) who had undergone temporal lobectomy and 18 control subjects. We measured hippocampal volumes on high- resolution coronal magnetization-prepared rapid gradient echo scans. Apparent diffusion coefficients (ADCs) for the entire hippocampus and three arbitrarily defined areas of interest within the hippocampal head, body, and tail were measured from the coregistered ADC map. Pathology was reviewed and correlated with imaging findings.

RESULTS

Fourteen of 22 patients had hippocampal atrophy on MRI (defined as volume asymmetry greater than 2 SDs compared with asymmetry in the control group). Overall, resected hippocampi (n = 22) were significantly smaller than contralateral hippocampi as well as ipsilateral hippocampi in controls. ADCs were significantly higher in resected hippocampi than contralateral hippocampi as well as ipsilateral hippocampi in controls. These differences were also observed within the three areas of interest. ADCs in the hippocampi contralateral to the epileptogenic zone (n = 22) were also higher than in ipsilateral hippocampi in controls. In the subgroup of eight patients with nonlateralizing conventional MRIs, ADCs of resected hippocampi were not significantly different compared with the contralateral side. Pathology in these patients revealed gliosis only without apparent neuron loss.

CONCLUSION

Interictal apparent diffusion coefficients confirm lateralization in patients with hippocampal atrophy on standard temporal lobe protocol MRI. However, they do not provide lateralizing information in patients with nonlateralizing conventional MRI.

Decreased thickness of primary motor cortex in primary lateral sclerosis

BACKGROUND AND PURPOSE

Primary lateral sclerosis (PLS) is a rare form of motor neuron disease characterized by upper motor neuron dysfunction. Because pathologic examination has revealed a loss of neurons in the motor cortex of patients with PLS, we sought to confirm and extend this finding by using MR imaging to measure cortical thickness.

METHODS

Seven patients with PLS and 7 age-matched neurologically normal control subjects were examined with heavily T1-weighted short-tau inversion recovery (STIR) MR imaging performed at 3T. Cortical thickness in the anterior and posterior banks of both the central and precentral sulci were measured.

RESULTS

Primary motor cortex (M1) was significantly thinner in patients with PLS than M1 in healthy control subjects, measuring 2.32 +/- 0.21 mm compared with 2.79 +/- 0.18 mm (P = .0008). Cortical thickness did not differ between the 2 groups for primary sensory cortex or for the anterior or posterior banks of the precentral sulcus. Therefore, loss of gray matter was specific to motor cortex. Although this difference was modest, cortical thickness discriminated between the 2 groups; only 1 PLS case was within the range of normal measurements.

CONCLUSION

Decreased thickness of M1 on the anterior bank of the precentral sulcus in patients with PLS, demonstrable by MR imaging, indicates a selective loss of upper motor neurons in this disease. Measurements of cortical thickness by MR imaging may provide a useful biomarker for diagnosis and study of upper motor neuron diseases.

Triple-stimulation technique in multifocal neuropathy with conduction block

In patients with multifocal neuropathy with conduction block (CB), CBs located between the root and Erb's point are not detected in nerve conduction studies. We therefore examined whether the triple-stimulation technique (TST) might provide a useful means of detecting CB proximal to Erb's point. Clinical assessments, extensive nerve conduction studies (NCS), conventional transcranial magnetic stimulation, and TST were performed on 10 patients with multifocal motor neuropathy with CB (MMNCB) and 6 patients with Lewis-Sumner syndrome. Conduction blocks located proximal to Erb's point were detected in 9 patients. Of the CBs, 58% were associated with muscle weakness. The use of TST to detect proximal CB improved the sensitivity of the American Association of Neuromuscular and Electrodiagnostic Medicine criteria for definite or probable MMNCB from 60% to 90%. Thus, the TST is a useful means for detection of proximal CB and gives NCS considerable additional diagnostic power.

Statins, Neuromuscular Degenerative Disease and an Amyotrophic Lateral Sclerosis-Like Syndrome

BACKGROUND

The WHO Foundation Collaborating Centre for International Drug Monitoring (Uppsala Monitoring Centre [UMC]) has received many individual case safety reports (ICSRs) associating HMG-CoA reductase inhibitor drug (statin) use with the occurrence of muscle damage, including rhabdomyolysis, and also peripheral neuropathy. A new signal has now appeared of disproportionally high reporting of upper motor neurone lesions.

AIM AND SCOPE

The aim of this paper is to present the upper motor neurone lesion cases, with other evidence, as a signal of a relationship between statins and an amyotrophic lateral sclerosis (ALS)-like syndrome. The paper also presents some arguments for considering that a spectrum of severe neuromuscular damage may be associated with statin use, albeit rarely. The paper does not do more than raise the signal for further work and analysis of what must be regarded as a potentially very serious and perhaps avoidable or reversible adverse reaction, though it also suggests action to be taken if an ALS-like syndrome should occur in a patient using statins.

METHODS

The 43 reports accounting for the disproportional reports in Vigibase (the database of the WHO Programme for International Drug Monitoring) are summarised and analysed for the diagnosis of an ALS-like syndrome. The issues of data quality and potential reporting bias are considered.

RESULTS

'Upper motor neurone lesion' is a rare adverse event reported in relationship to drugs in Vigibase (a database containing nearly 4 million ICSRs). Of the total of 172 ICSRs on this reported term, 43 were related to statins, of which 40 were considered further: all but one case was reported as ALS. In 34/40 reports a statin was the sole reported suspected drug. The diagnostic criteria were variable, and seven of the statin cases also had features of peripheral neuropathy. Of a total of 5534 ICSRs of peripheral neuropathy related to any drug in Vigibase, 547 were on statins. The disproportional reporting of statins and upper motor neurone lesion persisted after age stratification, and such disproportionality was not seen for statins and Parkinson's disease, Alzheimer's disease, extrapyramidal disorders, or multiple sclerosis-like syndromes.

DISCUSSION

Because the cases were sometimes atypical we propose the use of the term 'ALS-like syndrome' and speculate whether this is part of a spectrum of rare neuromuscular damage. The diagnosis of ALS is often problematic, and the insidiousness and chronicity of the disease make causality with a drug difficult to assess. The disproportionally high reporting makes this an important signal nevertheless, since ALS is serious clinically and statins are so widely used. Wide use of the statins also makes a chance finding more probable, but is unlikely to cause disproportional reporting when there are no obvious biases identified.

CONCLUSION

We emphasise the rarity of this possible association, and also the need for further study to establish whether a causal relationship exists. We do advocate that trial discontinuation of a statin should be considered in patients with serious neuromuscular disease such as the ALS-like syndrome, given the poor prognosis and a possibility that progression of the disease may be halted or even reversed.

Two cases of spinocerebellar ataxia accompanied by involvement of the skeletal motor neuron system and bulbar palsy

We report two patients with spinocerebellar ataxia (SCA) with cranial and spinal motor neuron involvement. They initially presented with cerebellar ataxia, followed by bulbar palsy and limb motor neuron sign. One of the patients had a brother with allied disorder. SCA type 1 (SCA1), SCA3 and SCA6 have been reported to involve the motor neuron system, but they were excluded by DNA analyses in the present two patients. These two patients may form a distinct disease entity among SCAs.

Updating motor unit number estimation (MUNE)

Motor unit number estimation (MUNE) is a unique electrophysiologic technique that can provide a numeric estimate of the number of axons innervating a muscle or group of muscles. The first technique was first described in 1971, and since then different techniques have been developed to address specific methodologic issues. The field was reviewed in this journal in 2001, and this update covers new information and uses of MUNE over the past five years. These include models of muscles that allow evaluation of MUNE techniques and comparisons between techniques. There have been further investigations of specific technical aspects of MUNE. Modifications to MUNE techniques have been offered that permit more rapid acquisition of data. MUNE has been used in clinical situations to elucidate the pathophysiology features of axonal loss in a number of disorders. There is now more experience with MUNE as endpoint measures in clinical trials.

Primary lateral sclerosis

The spectrum of motor neuron diseases ranges from disorders that clinically are limited to lower motor neurons to those that exclusively affect upper motor neurons. Primary lateral sclerosis (PLS) is the designation for the syndrome of progressive upper motor neuron dysfunction when no other etiology is identified. Distinction between PLS and the more common amyotrophic lateral sclerosis (ALS) relies primarily on recognition of their symptoms and signs, as well as on ancillary, although non-specific, laboratory data. In this review, we survey the history of PLS from the initial descriptions to the present. We discuss the role of laboratory, electrodiagnostic, and imaging studies in excluding other diagnoses; the findings from major case series of PLS patients; and proposed diagnostic criteria. Consistent differences are evident in patients classified as PLS compared to those with ALS, indicating that, despite its limitations, this clinical designation retains important utility.

Frequent atrophic groups with mixed-type myofibers is distinctive to motor neuron syndromes

This study was performed to determine whether there are distinctive features to the pattern of muscle denervation in motor neuron disease. We first compared muscle biopsies from patients with amyotrophic lateral sclerosis (ALS) or Kennedy's disease with other causes of denervation. Groups of atrophic muscle fibers, with individual groups containing both fiber types I and II, occurred frequently in motor neuron disease but not other causes of denervation. We then identified 11 additional muscle biopsies with frequent atrophic groups containing mixed fiber types. Chart review revealed that 10 patients had a final diagnosis of motor neuron disease or ALS and one had multifocal motor neuropathy. We conclude that muscle biopsy may have diagnostic utility early in the course of motor neuron disease. The muscle biopsy pattern of frequent atrophic groups containing mixed fiber types should suggest a diagnosis of a motor neuron syndrome or motor neuropathy.

Transcallosal inhibition in amyotrophic lateral sclerosis

OBJECTIVE

Assessment of upper motor neuron (UMN) involvement is essential for the diagnosis of amyotrophic lateral sclerosis (ALS). In a number of ALS cases, mirror movements (MM) suggest an involvement of transcallosal fibre tracts in conjunction with UMN involvement. The present study analysed whether deficient transcallosal inhibition (TI) tested by TMS enables detection of cortical affection in ALS, even at early stages of the disease.

METHODS

In three patients with definite ALS and 12 patients with early ALS (aged 64.1+/-7.8 years) TMS investigation included analysis of contralateral (cMEP) and ipsilateral (iMEP) motor evoked potentials as well as measurement of TI (latency, duration) with recording from both first dorsal interosseus muscles.

RESULTS

Clinical UMN signs were present in four patients. 83.3% of patients showed a pathological TI (prolongation or loss of TI). Five out of eight ALS patients showing a pathological TI had no clinical UMN signs. Two of these patients showed MM. One patient displayed also pathological findings in TI investigation.

CONCLUSIONS

Our findings suggest a functional deficit of transcallosal fibre tracts even at early stages of the disease still lacking clinical UMN signs.

SIGNIFICANCE

Measurement of TI tested by TMS can detect an involvement of the cortical output system in ALS and may be helpful in an early assessment of the diagnosis.

Upper motor neuron involvement in X-linked recessive bulbospinal muscular atrophy

OBJECTIVE

Clinicopathological findings of X-linked recessive bulbospinal muscular atrophy (SBMA) are indicative of lower motor neuron and primary sensory neuron involvement. The aim of our study was to investigate the presence of subclinical upper motor neuron (UMN) dysfunction in this disease.

METHODS

Two siblings with clinical presentation, routine electrophysiological tests, histopathological features of muscle and nerve biopsies and genetic testing consistent with diagnosis of SBMA underwent transcranial magnetic stimulation (TMS). The analysed parameters were motor evoked potential (MEP) threshold, silent period (SP) and central motor conduction time. Intracortical inhibition with paired pulses from 1 to 6ms interstimulus intervals (ISIs) was evaluated in the older brother.

RESULTS

MEP parameters were significantly altered in limb and cranial muscles and MEP suppression after paired stimulation significantly reduced in the older brother. MEP abnormalities were present in one lower limb, but SP abolished in all limbs, in the younger brother.

CONCLUSIONS

Subclinical involvement of UMNs may be present in patients affected by SBMA. This finding suggests that the array of neuronal systems whose function may be affected by the pathogenic process of SBMA is larger than it was considered so far.

SIGNIFICANCE

TMS is a sensitive diagnostic tool for the identification of UMN dysfunction and should be included in the diagnostic evaluation of patients with SBMA.

Long-term neurodevelopmental outcome of preterm children with unilateral cerebral lesions diagnosed by neonatal ultrasound

OBJECTIVE

Little information is available on long-term neurodevelopmental outcome of preterm infants with unilateral cerebral lesions detected by neonatal cranial ultrasound. This study aims to investigate the long-term outcome in a cohort of very preterm infants with unilateral cerebral lesions acquired in the perinatal period.

METHODS

A prospective cohort study of 668 preterm infants (<33 weeks gestation; birth years 1985-1991) at a single tertiary perinatal centre in the UK. All infants had serial cranial ultrasound examination in the neonatal period. Outcome was assessed at age 8 years with the Wechsler Intelligence Scales for Children (WISC-R), Test of Visuo-motor Integration (VMI) and the Test of Motor Impairment (TOMI).

RESULTS

Of the 668 infants, 369 infants had normal ultrasound scans. Two hundred and ninety nine children had bilateral parenchymal or non-parenchymal lesions (57 left-sided, 41 right-sided, 201 bilateral). Five hundred and thirty four (79%) children attended follow-up at age 8 years. Mean Full Scale IQ (FSIQ) was 101 (SD+/-16), 93 (SD+/-17), 102 (SD+/-17) and 91 (SD+/-21) for normal, left-sided, right-sided and bilateral lesion groups respectively. In all groups verbal IQ (VIQ) was higher than performance IQ (PIQ). Scores of FSIQ, VIQ and PIQ, VMI and TOMI were significantly different between the groups. After exclusion of children with parenchymal lesions, however, the difference was only significant for the TOMI scores. In all tests, children with left-sided lesions performed poorer than children with right-sided lesions.

CONCLUSIONS

In this cohort of preterm infants with unilateral cerebral lesions, verbal function was preserved over non-verbal function independently of the side of lesion. Furthermore, the results suggest that the neurodevelopmental outcome of children with left-sided lesions is less favourable than that of children with right-sided lesions.

Children with congenital spastic hemiplegia obey Fitts' Law in a visually guided tapping task

Fitts' Law is commonly found to apply to motor tasks involving precise aiming movements. Children with cerebral palsy (CP) have severe difficulties in such tasks and it is unknown whether they obey Fitts' Law despite their motor difficulties. If Fitts' Law still does apply to these children, this would indicate that this law is extremely robust and that even performance of children with damaged central nervous systems can adhere to it. The integrity of motor control processes in spastic CP is usually tested in complex motor tasks, making it difficult to determine whether poor performance is due to a motor output deficit or to problems related to cognitive processes since both affect movement precision. In the present study a simple task was designed to evaluate Fitts' Law. Tapping movements were evaluated in 22 children with congenital spastic hemiplegia (CSH) and 22 typically developing children. Targets (2.5 and 5 cm in width) were placed at distances of 10 and 20 cm from each other in order to provide Indices of Difficulty (ID) of 2-4 bits. Using this Fitts' aiming task, prolonged reaction and movement time (MT) were found in the affected hand under all conditions in children with CSH as compared to controls. Like in the control group, MT in children with CSH was related to ID. The intercept 'a', corresponding to the time required to realize a tapping movement, was higher in the affected hand of the children in the CSH group. Although, the slope b (which reflects the sensitivity of the motor system to a change in difficulty of the task) and the reciprocal of slope (that represents the cognitive information processing capacity, expressed in bits/s) were similar in both groups. In conclusion, children with CSH obey Fitts' Law despite very obvious limitations in fine motor control.

Multifocal motor neuropathy with and without conduction block: a single entity?

OBJECTIVE

To assess if multifocal motor neuropathy (MMN) with and MMN without conduction block (CB) are similar or distinct diseases.

METHODS

The authors reviewed the clinical features and responses to IV immunoglobulin (IVIg) treatment of patients with MMN with and without CB at diagnosis, after 4 years of follow-up and at the last examination. They included all patients showing clinical features of MMN who had been followed for at least 4 years: All had asymmetric purely motor weakness with a peripheral nerve distribution, without any sensory, bulbar, or respiratory signs and without any upper motor neuron involvement.

RESULTS

Twenty patients had CB and 13 had no CB. Median follow-up time was 7 years. There were no differences between the two groups in term of age, sex, time from onset to diagnosis, anti-GM1 antibody titers, or CSF data. Nerve distribution, number of affected limb regions, predominant weakness in distal upper extremities, asymmetric weakness, cramps, fasciculations, and Medical Research Council sum-scores in upper and lower limbs were comparable at diagnosis, 4 years of follow-up, and last examination. Few significant differences were observed. Involvement of median nerve was less frequent at 4 years of follow-up (14/20 vs 4/13; p = 0.027) and at the last examination (17/20 vs 5/13; p = 0.009) in patients without CB. Proximal weakness was less frequent in patients with MMN without CB at the last examination (7/20 vs 0/13; p = 0.027). Fewer nerves were involved in patients without CB at the last examination (4.5 vs 2; p = 0.04). Efficacy of IVIg was similar in MNN patients without CB (8/13) and with CB (14/20; p > 0.05).

CONCLUSION

After a median follow-up time of 7 years, patients with and without conduction block showed similar clinical features and a similar response to IV immunoglobulin treatment.

Criteria for conduction block based on computer simulation studies of nerve conduction with human data obtained in the forearm segment of the median nerve

The finding of conduction block (CB) on nerve conduction studies supports the diagnosis of potentially treatable immune-mediated neuropathies. CB in a number of axons may result in reduction of the compound muscle action potential (CMAP) on proximal versus distal stimulation (decrement). Decrement may also result from increased temporal dispersion (TD) as this leads to desynchronization and phase cancellation of the motor unit action potentials (MUAPs) out of which the CMAP is built up; polyphasia of MUAPs possibly yields additional decrement. To prove the occurrence of CB, decrement has to be larger than can be explained by increased TD or increased phase cancellation. This was established previously by simulations using MUAPs recorded in rats assuming maximal TD. Unfortunately, criteria based on human data and criteria for nerves with limited TD are not available. In the present study, criteria for CB were derived using simulations with thenar surface recorded MUAPs affected by collateral reinnervation that were obtained in patients with lower motor neurone disease (LMND). The effect of TD on decrement was determined for a wide range of TDs in the forearm segment of the median nerve and the segment distal to this. Our criteria for CB were based on area decrement because this was less influenced by TD and more by CB than amplitude decrement. The maximal area decrement in the forearm segment increased as TD in the forearm segment increased but decreased as TD in the distal segment increased. This suggests that, when desynchronization and phase cancellation occur in the distal segment due to TD, less phase cancellation and, therefore, less decrement can occur due to TD in the forearm. The finding that duration prolongation on proximal versus distal stimulation reflected TD within the forearm segment and that distal duration reflected TD in the distal segment allowed proposal of a more flexible set of criteria for forearm segments when TD in the forearm segment is limited or TD in the distal segment is pronounced. A separate investigation showed that the maximal TD in chronic inflammatory demyelinating polyneuropathy was within the range of our simulations, indicating that these were realistic. Our criteria were validated retrospectively in patients with multifocal motor neuropathy and patients with LMND. In the forearm segment of the median nerve, our criteria were more sensitive and equally specific for CB as compared with criteria for CB based on the study using rats. Our criteria have to be evaluated prospectively.

Activity-dependent conduction block in multifocal motor neuropathy: Magnetic fatigue test

BACKGROUND

Multifocal motor neuropathy (MMN) is often misdiagnosed as motor neuron disease, especially when overt evidence of conduction block (CB) is lacking. Activity-dependent CB (ADCB), defined as transient CB induced by brief exercise, has been recently found in MMN but not in ALS.

METHODS

To test the diagnostic utility of ADCB for differentiating MMN from ALS, the authors recorded the compound muscle action potentials (CMAPs) from small hand muscles by magnetically stimulating nerve roots before and after 1 minute of maximal voluntary contraction (magnetic fatigue test). They examined nine patients with MMN with unequivocal clinical responses to IV immunoglobulins (IVIgs), yet lacked CB according to the conventional criteria.

RESULTS

Six MMN patients had postexercise CB/temporal dispersion maximum in the immediate postexercise period. ADCB in an MMN patient improved after IVIg. Further analysis revealed that prolongation of the duration from the onset to the positive peak of the CMAP was the most sensitive indicator for MMN, presumably because the phase cancellation obscures the abnormalities of the other parameters.

CONCLUSION

The magnetic fatigue test is useful in detecting mild conduction block presumably located in a proximal nerve segment in patients with multifocal motor neuropathy who do not fulfill its conventional electrodiagnostic criteria.

Anti-tissue transglutaminase IgA antibodies in peripheral neuropathy and motor neuronopathy

OBJECTIVES

The aim of the study was to investigate the occurence of anti-tissue transglutaminase antibodies (tTGA) in peripheral nerve disorders, and to correlate them with neurophysiologic findings and anti-glycolipid antibodies.

MATERIALS AND METHODS

We examined tTGA immunoglobulin-A serum level from 220 patients with polyneuropathy (acute inflammatory: n=90; chronic inflammatory: n=56; non-inflammatory: n=74) and 110 with motor neuron disease (MND).

RESULTS

Seven of the 330 neurologic patients (2.1%, six with polyneuropathy and one with MND) were positive for tTGA. Sixty-one of the 330 neurologic patients (18.4%) had slightly increased tTGA values compared with healthy controls. Increased tTGA values were associated with greater impairment of neurophysiologic findings, but not with the presence of anti-glycolipid antibodies.

CONCLUSIONS

We found a high prevalence of tTGA reactivity in patients with peripheral nerve disorders or MND. However, we were unable to demonstrate an increased risk of celiac disease in these diseases.

Clinical signs of accessory nerve palsy

BACKGROUND

Injury to the spinal accessory nerve causes paralysis of the trapezius muscle, which is a painful and disabling condition. Many injuries are iatrogenic. Diagnosis is often made after a long delay, suggesting that current clinical signs are inadequate.

METHODS

Accessory nerve palsy is known to be a cause of winging of the scapula. Observation of six patients with accessory nerve palsy has shown that winging of the scapula is most prominent when the patient actively externally rotates the shoulder against resistance.

RESULTS

This is in contrast to the other causes of winging of the scapula including long thoracic nerve palsy and muscular dystrophy, where the scapula is most prominent on flexion or abduction of the shoulder.

CONCLUSION

We propose that the resisted active external rotation test should be regarded as the key clinical sign for accessory nerve palsy.

[Differential diagnosis and atypical subsets of amyotrophic lateral sclerosis]

Amyotrophic lateral sclerosis (ALS) is a progressive degeneration of upper and lower motor neurons. In the absence of any validated biological marker, the diagnosis of ALS depends upon recognition of characteristic symptoms and signs together with supportive electrophysiological findings. The diagnosis of ALS is easy to recognize in its fully developed form but during the early stages both false positive and false negative diagnoses are common. In clinical practice, diagnostic difficulties mostly arise with patients who present either with only upper motor neuron, or with only lower motor neuron signs. It may be difficult to distinguish ALS with clinically predominant lower motor neuron involvement from alternative diagnoses including spinal atrophies of adult onset, Kennedy's disease, inclusion body myositis and motor neuropathies with conduction blocks. The diagnosis of ALS related syndromes (progressive muscular atrophy, primary lateral sclerosis and progressive bulbar palsy) requires the elimination of alternate diagnoses. This paper reviews the main characteristics of diseases mimicking ALS and the atypical subsets of ALS.

Amyotrophic Lateral Sclerosis: Diffusion-Tensor and Chemical Shift MR Imaging at 3.0 T

PURPOSE

To prospectively determine whether diffusion-tensor magnetic resonance (MR) imaging in conjunction with two-dimensional chemical shift imaging can assist in identifying upper motor neuron involvement and whether disease severity and duration can be predicted based on imaging parameters in patients with amyotrophic lateral sclerosis (ALS).

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. Fifteen patients with ALS (12 men, three women; mean age, 57.3 years) with clinical evidence of upper motor neuron involvement and 10 healthy control subjects (five men and five women; mean age, 49.4 years) were studied. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were measured from the corticospinal tracts at the level of the internal capsule. Average N-acetylaspartate (NAA)/creatine-phosphocreatine (Cr) and NAA/choline-containing compounds (Cho) ratios were calculated from the precentral gyrus. Student t test, multiple linear regression analysis, and Spearman correlation coefficients were employed to quantify relationships between imaging and clinical parameters.

RESULTS

Patients with ALS exhibited significantly reduced FA values and NAA/Cr and NAA/Cho ratios compared with values in control subjects (P<.05) for both affected and nonaffected sides of the brain. ADC was elevated significantly in the affected side (P<.05) and was an independent predictor of disease duration after adjusting for age; however, FA values and NAA/Cr ratios for the affected side were even stronger predictors of disease duration. Moderate but statistically significant correlation was found between the FA values for the affected side and the ALS Functional Rating Scale Revised (ALSFRS-R) score (r=0.51, P<.05). The NAA/Cr ratio also correlated with both the ALSFRS-R and upper motor neuron scores (r=0.50 and 0.54, respectively; P<.05).

CONCLUSION

Diffusion-tensor and two-dimensional chemical shift MR imaging spectroscopy can be used to identify upper motor neuron involvement and predict disease duration in patients with ALS.

[Amyotrophic lateral sclerosis: differential diagnosis and frontier forms]

Amyotrophic lateral sclerosis (ALS) may be mimicked by disorders affecting the different levels of the motor system from cortex to muscle. Clinical heterogeneity is a feature of both ALS and related syndromes allowing for a large differential diagnosis. During the initial stage of a motor disorder false positive and false negative diagnoses of ALS are possible. Examples of disorders that should not be misdiagnosed as ALS, because their prognosis and treatment differ, are multifocal motor neuropathy, Kennedy's bulbospinal atrophy, cervical myelopathy, hyperthyroidism and hyperparathyroidism. Syndromes remote from polio and radiation treatments should be recognised. Eventually, frontier forms of ALS with signs restricted to either the upper or lower motor neurons deserve particular attention. Electrodiagnosis is pivotal to disclose signs and extension of the peripheral motor neuron, to detect and quantify cortico-spinal involvement, to search for specific signs of conditions that mimic ALS. Until specific markers become available, clinical evaluation supported by electrodiagnosis and other ancillary tests are crucial to provide with the correct diagnosis, prognosis and treatment.

The molecular genetics of non-ALS motor neuron diseases

Hereditary disorders of voluntary motor neurons are individually relatively uncommon, but have the potential to provide significant insights into motor neuron function in general and into the mechanisms underlying the more common form of sporadic Amyotrophic Lateral Sclerosis. Recently, mutations in a number of novel genes have been associated with Lower Motor Neuron (HSPB1, HSPB8, GARS, Dynactin), Upper Motor Neuron (Spastin, Atlastin, Paraplegin, HSP60, KIF5A, NIPA1) or mixed ALS-like phenotypes (Alsin, Senataxin, VAPB, BSCL2). In comparison to sporadic ALS these conditions are usually associated with slow progression, but as experience increases, a wide variation in clinical phenotype has become apparent. At the molecular level common themes are emerging that point to areas of specific vulnerability for motor neurons such as axonal transport, endosomal trafficking and RNA processing. We review the clinical and molecular features of this diverse group of genetically determined conditions and consider the implications for the broad group of motor neuron diseases in general.