Tremor in motor neuron disease may be central rather than peripheral in origin.

BACKGROUND AND PURPOSE: Motor neuron disease (MND) refers to a spectrum of degenerative diseases affecting motor neurons. Recent clinical and post-mortem observations have revealed considerable variability in the phenotype. Rhythmic involuntary oscillations of the hands during action, resembling tremor, can occur in MND, but their pathophysiology has not yet been investigated. METHODS: A total of 120 consecutive patients with MND were screened for tremor. Twelve patients with action tremor and no other movement disorders were found. Ten took part in the study. Tremor was recorded bilaterally using surface electromyography (EMG) and triaxial accelerometer, with and without a variable weight load. Power spectra of rectified EMG and accelerometric signal were calculated. To investigate a possible cerebellar involvement, eyeblink classic conditioning was performed in five patients. RESULTS: Action tremor was present in about 10% of our population. All patients showed distal postural tremor of low amplitude and constant frequency, bilateral with a small degree of asymmetry. Two also showed simple kinetic tremor. A peak at the EMG and accelerometric recordings ranging from 4 to 12 Hz was found in all patients. Loading did not change peak frequency in either the electromyographic or accelerometric power spectra. Compared with healthy volunteers, patients had a smaller number of conditioned responses during eyeblink classic conditioning. CONCLUSIONS: Our data suggest that patients with MND can present with action tremor of a central origin, possibly due to a cerebellar dysfunction. This evidence supports the novel idea of MND as a multisystem neurodegenerative disease and that action tremor can be part of this condition.

Lithium in patients with amyotrophic lateral sclerosis (LiCALS): a phase 3 multicentre, randomised, double-blind, placebo-controlled trial.

BACKGROUND: Lithium has neuroprotective effects in cell and animal models of amyotrophic lateral sclerosis (ALS), and a small pilot study in patients with ALS showed a significant effect of lithium on survival. We aimed to assess whether lithium improves survival in patients with ALS. METHODS: The lithium carbonate in amyotrophic lateral sclerosis (LiCALS) trial is a randomised, double-blind, placebo-controlled trial of oral lithium taken daily for 18 months in patients with ALS. Patients aged at least 18 years who had ALS according to the revised El Escorial criteria, had disease duration between 6 and 36 months, and were taking riluzole were recruited from ten centres in the UK. Patients were randomly assigned (1:1) to receive either lithium or matched placebo tablets. Randomisation was via an online system done at the level of the individual by block randomisation with randomly varying block sizes, stratified by study centre and site of disease onset (limb or bulbar). All patients and assessing study personnel were masked to treatment assignment. The primary endpoint was the rate of survival at 18 months and was analysed by intention to treat. This study is registered with Eudract, number 2008-006891-31. FINDINGS: Between May 26, 2009, and Nov 10, 2011, 243 patients were screened, 214 of whom were randomly assigned to receive lithium (107 patients) or placebo (107 patients). Two patients discontinued treatment and one died before the target therapeutic lithium concentration could be achieved. 63 (59%) of 107 patients in the placebo group and 54 (50%) of 107 patients in the lithium group were alive at 18 months. The survival functions did not differ significantly between groups (Mantel-Cox log-rank χ(2) on 1 df=1·64; p=0·20). After adjusting for study centre and site of onset using logistic regression, the relative odds of survival at 18 months (lithium vs placebo) was 0·71 (95% CI 0·40-1·24). 56 patients in the placebo group and 61 in the lithium group had at least one serious adverse event. INTERPRETATION: We found no evidence of benefit of lithium on survival in patients with ALS, but nor were there safety concerns, which had been identified in previous studies with less conventional designs. This finding emphasises the importance of pursuing adequately powered trials with clear endpoints when testing new treatments. FUNDING: The Motor Neurone Disease Association of Great Britain and Northern Ireland.

Myasthenia gravis and neuromyelitis opica: A causal link.

Neuromyelitis Optica (NMO) and Myasthenia Gravis (MG) are rare antibody mediated disorders of the central nervous system (CNS) and neuromuscular junction (NMJ) respectively. Both diseases are predominantly mediated by IgG1 antibodies that activate complement. There have been increasing reports of patients who develop both disorders. Given the rarity of both diseases it would seem that these occurrences are not purely coincidental. There is heterogeneity between the cases described in the literature but common trends are observed in patients who develop both disorders. Most patients described are female. Typically the MG precedes the NMO and the majority of patients have undergone thymectomy. Generally, the symptoms of MG are mild but the NMO tends to follow a more aggressive clinical course. The pathogenesis of NMO in combination with MG is unknown, but thymectomy has been implicated in a subset of patients. We present the case of a female patient who developed NMO on a background of sero-positive MG and discuss the relevant literature.

Fatal familial insomnia: a new Austrian family.

We present clinical, pathological and molecular features of the first Austrian family with fatal familial insomnia. Detailed clinical data are available in five patients and autopsy in four patients. Age at onset of disease ranged between 20 and 60 years, and disease duration between 8 and 20 months. Severe loss of weight was an early symptom in all five patients. Four patients developed insomnia and/or autonomic dysfunction, and all five patients developed motor abnormalities. Analysis of the prion protein (PrP) gene revealed the codon 178 point mutation and methionine homozygosity at position 129. In all brains, neuropathology showed widespread cortical astrogliosis, widespread brainstem nuclei and tract degeneration, and olivary 'pseudohypertrophy' with vacuolated neurons, in addition to neuropathological features described previously, such as thalamic and olivary degeneration. Western blotting of one brain and immunocytochemistry in four brains revealed quantitative and regional dissociation between PrP(res)(the protease resistant form of PrP) deposition and histopathology. In the cerebellar cortex of one patient, PrP(res) deposits were prominent in the molecular layer and displayed a peculiar patchy and strip-like pattern with perpendicular orientation to the surface. In another patient, a single vacuolated neuron in the inferior olivary nuclei contained prominent intravacuolar granular PrP(res) deposits, resembling changes of brainstem neurons in bovine spongiform encephalopathy.

Molecular screening of sheep for bovine spongiform encephalopathy.

Bovine spongiform encephalopathy (BSE) may have transmitted to sheep through feed and pose a risk to human health. Sheep BSE cannot be clinically distinguished from scrapie, and conventional strain typing would be impractical on a significant scale. As human prion strains can be distinguished by differences in prion protein (PrPsc) conformation and glycosylation we have applied PrP(Sc) typing to sheep. We found multiple Western blot patterns of PrP(Sc) in scrapie, consistent with the known scrapie strain diversity in sheep. Sheep passaged BSE showed a PrP(Sc) banding pattern similar to BSE passaged in other species [Collinge, J., Sidle, K.C.L., Meads, J., Ironside, J. and Hill, A.F., Nature, 383 (1996) 685-690], both in terms of fragment size following proteinase K cleavage and abundance of diglycosylated PrP. However, none of the historical or contemporary scrapie cases studied had a PrP(Sc) type identical to sheep BSE. While more extensive studies, including sheep of all PrP genotypes, will be required to fully evaluate these findings, these results suggest that large scale screening of sheep for BSE may be possible.

Molecular analysis of prion strain variation and the aetiology of 'new variant' CJD.

Strains of transmissible spongiform encephalopathies are distinguished by differing physicochemical properties of PrPSc, the disease-related isoform of prion protein, which can be maintained on transmission to transgenic mice. 'New variant' Creutzfeldt-Jakob disease (CJD) has strain characteristics distinct from other types of CJD and which resemble those of BSE transmitted to mice, domestic cat and macaque, consistent with BSE being the source of this new disease. Strain characteristics revealed here suggest that the prion protein may itself encode disease phenotype.

Genetic basis of Creutzfeldt-Jakob disease in the United Kingdom: a systematic analysis of predisposing mutations and allelic variation in the PRNP gene.

Creutzfeldt-Jakob disease (CJD) is a transmissible neurodegenerative disorder characterized by the accumulation of aggregates of a cellular protein, PrP, in the brain. In both human and animals, genetic alterations to the gene encoding PrP (PRNP in human) modulate susceptibility to CJD. The recent epidemic of bovine spongi-form encephalopathy in the UK has raised the possibility of transmission from animal produce to humans. To provide a baseline against which to assess possible risk factors, we have determined the frequencies of predisposing mutations and allelic variants in PRNP and their relative contributions to disease. Systematic PRNP genotype analysis was performed on suspected CJD cases referred to the National Surveillance Unit in the UK over the period 1990-1993. Inspection of 120 candidate cases revealed 67 patients with definite and probable CJD, based on clinical and neuropathological criteria. No PRNP mutations were detected in any of the remaining 53 patients assessed as "non-CJD". A disease-associated mutation in the PRNP gene was identified in nine (13.4%) definite and probable cases of CJD, a reliable estimate of the incidence of PRNP-related inherited CJD based on a prospective epidemiological series. Within the group of sporadic CJD patients (lacking PRNP mutations), we confirmed that the genotype distribution with respect to the common methionine/valine (Met/Val) polymorphism at codon 129 within PRNP was significantly different from the normal Caucasian population. The incidence of Met homozygosity at this site was more than doubled and correlated with increased susceptibility to the development of sporadic CJD. Unlike other recent studies, Val homozygosity was also confirmed to be a significant risk factor in sporadic CJD, with the relative risks for the three genotypes Met/Met: Val/Val:Met/Val being 11:4:1.

Unaltered susceptibility to BSE in transgenic mice expressing human prion protein.

Prion diseases are transmissible neurodegenerative conditions of humans and animals. Prions consist principally of a post-translationally modified form of prion protein (PrP), PrP(Sc), which is partly protease resistant. Transmission of prion diseases between species is limited by a 'species barrier' determined in part by the degree of sequence homology between host PrP and inoculated PrP(Sc) (ref.3) and by prion strain type. The epidemic of bovine spongiform encephalopathy (BSE) in the United Kingdom and other countries has led to concerns that transmission to humans may occur by dietary exposure. BSE appears to be caused by a single strain, distinct from those of natural or experimental scrapie, which is also seen in the new prion diseases of cats and ruminants that have presumably arisen from dietary BSE exposure. Here we show that transgenic mice expressing human PrP in addition to mouse PrP can generate human PrP(Sc) and 'human' prions. These mice therefore provide a model to study experimentally the species barrier limiting BSE transmission to humans. Incubation periods to BSE in transgenic mice are not shortened by expression of human PrP, and only mouse PrP(Sc) is produced in response to such challenge.

Rescue of neurophysiological phenotype seen in PrP null mice by transgene encoding human prion protein.

The prion protein (PrP) is central to the aetiology of the prion diseases, transmissible neurodegenerative conditions of humans and animals. PrP null mice show abnormalities of synaptic neurophysiology, in particular weakened GABAA receptor-mediated fast inhibition and impaired long-term potentiation in the hippocampus. Here we demonstrate that this PrP null phenotype is rescued in mice with a high copy number of a transgene encoding human PrP but not in low copy number mice, confirming the specificity of the phenotype for loss of function of PrP. The ability of human PrP to compensate for loss of murine PrP will allow direct study of the functional consequences of the 18 human PrP mutations, which cause the inherited prion diseases; this phenotype can now form the basis of the first functional assay for PrP.

Transmission of Creutzfeldt-Jakob disease from humans to transgenic mice expressing chimeric human-mouse prion protein.

Transgenic (Tg) mice were constructed that express a chimeric prion protein (PrP) in which a segment of mouse (Mo) PrP was replaced with the corresponding human (Hu) PrP sequence. The chimeric PrP, designated MHu2MPrP, differs from MoPrP by 9 amino acids between residues 96 and 167. All of the Tg(MHu2M) mice developed neurologic disease approximately 200 days after inoculation with brain homogenates from three patients dying of Creutzfeldt-Jakob disease (CJD). Inoculation of Tg(MHu2M) mice with CJD prions produced MHu2MPrPSc (where PrPSc is the scrapie isoform of PrP); inoculation with Mo prions produced Mo-PrPSc. The patterns of MHu2MPrPSc and MoPrPSc accumulation in the brains of Tg(MHu2M) mice were different. About 10% of Tg(HuPrP) mice expressing HuPrP and non-Tg mice developed neurologic disease > 500 days after inoculation with CJD prions. The different susceptibilities of Tg(HuPrP) and Tg(MHu2M) mice to Hu prions indicate that additional species-specific factors are involved in prion replication. Diagnosis, prevention, and treatment of Hu prion diseases should be facilitated by Tg(MHu2M) mice.

Prion protein is necessary for normal synaptic function.

The prion diseases are neurodegenerative conditions, transmissible by inoculation, and in some cases inherited as an autosomal dominant disorder. They include Creutzfeldt-Jakob disease in humans and scrapie and bovine spongiform encephalopathy in animals. The prion consists principally of a post-translationally modified form of a host-encoded glycoprotein (PrPC), designated PrPSc (ref. 1); the normal cellular function of PrPC is, however, unknown. Although PrP is highly conserved among mammals and widely expressed in early embryogenesis, mice homozygous for disrupted PrP genes appear developmentally and behaviourally normal. PrP is a protein anchored to the neuronal surface by glycosylphosphatidylinositol, suggesting a role in cell signalling or adhesion. Here we report that hippocampal slices from PrP null mice have weakened GABAA (gamma-aminobutyric acid type A) receptor-mediated fast inhibition and impaired long-term potentiation. This impaired synaptic inhibition may be involved in the epileptiform activity seen in Creutzfeldt-Jakob disease and we argue that loss of function of PrPC may contribute to the early synaptic loss and neuronal degeneration seen in these diseases.

Deletions in the prion protein gene are not associated with CJD.

The human prion diseases (spongiform encephalopathies) Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler syndrome (GSS), are neurodegenerative disorders characterised by the accumulation of an abnormal isoform of the prion protein. The normal prion protein is a phosphatidyl inositol anchored, membrane bound sialoglycoprotein of widespread tissue distribution but expressed predominantly in the brain. 15% of prion diseases are autosomal dominant genetic disorders associated with mutations in the gene encoding the prion protein. To date six pathogenic amino acid substitutions have been identified in affected family members, in addition to five distinct insertional events which occur within a region of the protein comprising four tandem octapeptide repeats. We have investigated deletions within this region and have identified three specific deletions. We report here that these deletions are not associated with CJD and represent a new class of polymorphism within the prion protein gene.

Inherited prion disease (PrP lysine 200) in Britain: two case reports.

OBJECTIVE: To identify cases of inherited prion diseases in Britain and to assess their phenotypic features. DESIGN: Screening study of patients suspected clinically to have Creutzfeldt-Jakob disease and other neurodegenerative diseases by prion protein gene analysis. SETTING: Biochemical research department. SUBJECTS: Patients suspected to have Creutzfeldt-Jakob disease and other neurodegenerative diseases. RESULTS: Two patients with symptoms characteristic of sporadic Creutzfeldt-Jakob disease were found to have inherited prion protein disease (PrP lysine 200), with a mutation at codon 200 of the prion protein gene. Both were homozygous at codon 129 of the gene. One patient was a man aged 58 of British descent while the other was of Libyan Jewish origin. CONCLUSION: Two foci of inherited prion disease are known, among Libyan Jews and in Slovakia. A separate British focus of the disease may also exist. Heterozygosity at codon 129 may lead to reduced penetrance of the mutation.