Multidisciplinary Clinics in Neuromuscular Medicine

ABSTRACT

Multidisciplinary care is comprehensive, coordinated clinical care across medical disciplines and allied health professions. Neuromuscular disorders, such as amyotrophic lateral sclerosis and muscular dystrophies, are often associated with disabling weakness and extramuscular symptoms and may benefit from care in a model that consolidates numerous clinic visits into a single more efficient multidisciplinary clinic visit. The goal of the neuromuscular multidisciplinary care model is to improve patient outcomes, patient satisfaction, quality of life, access to medications and equipment, and survival. Although the costs of running a multidisciplinary clinic are high, they are likely associated with cost savings from the patient's perspective. Several barriers to acceptance of multidisciplinary clinics include the distance needed to travel to the clinic and the duration of the clinic visit. Telehealth multidisciplinary clinic visits may address some of these concerns. Further study is needed to understand the value of multidisciplinary clinics and is a necessary step toward creating a sustainable model.

Identification of quantitative trait loci for survival in the mutant dynactin p150Glued mouse model of motor neuron disease

Amyotrophic lateral sclerosis (ALS) is the most common degenerative motor neuron disorder. Although most cases of ALS are sporadic, 5-10% of cases are familial, with mutations associated with over 40 genes. There is variation of ALS symptoms within families carrying the same mutation; the disease may develop in one sibling and not in another despite the presence of the mutation in both. Although the cause of this phenotypic variation is unknown, it is likely related to genetic modifiers of disease expression. The identification of ALS causing genes has led to the development of transgenic mouse models of motor neuron disease. Similar to families with familial ALS, there are background-dependent differences in disease phenotype in transgenic mouse models of ALS suggesting that, as in human ALS, differences in phenotype may be ascribed to genetic modifiers. These genetic modifiers may not cause ALS rather their expression either exacerbates or ameliorates the effect of the mutant ALS causing genes. We have reported that in both the G93A-hSOD1 and G59S-hDCTN1 mouse models, SJL mice demonstrated a more severe phenotype than C57BL6 mice. From reciprocal intercrosses between G93A-hSOD1 transgenic mice on SJL and C57BL6 strains, we identified a major quantitative trait locus (QTL) on mouse chromosome 17 that results in a significant shift in lifespan. In this study we generated reciprocal intercrosses between transgenic G59S-hDCTN1 mice on SJL and C57BL6 strains and identified survival QTLs on mouse chromosomes 17 and 18. The chromosome 17 survival QTL on G93A-hSOD1 and G59S-hDCTN1 mice partly overlap, suggesting that the genetic modifiers located in this region may be shared by these two ALS models despite the fact that motor neuron degeneration is caused by mutations in different proteins. The overlapping region contains eighty-seven genes with non-synonymous variations predicted to be deleterious and/or damaging. Two genes in this segment, NOTCH3 and Safb/SAFB1, have been associated with motor neuron disease. The identification of genetic modifiers of motor neuron disease, especially those modifiers that are shared by SOD1 and dynactin-1 transgenic mice, may result in the identification of novel targets for therapies that can alter the course of this devastating illness.

Effect of sodium phenylbutyrate/taurursodiol on tracheostomy/ventilation-free survival and hospitalisation in amyotrophic lateral sclerosis: long-term results from the CENTAUR trial

BACKGROUND

Coformulated sodium phenylbutyrate/taurursodiol (PB/TURSO) was shown to prolong survival and slow functional decline in amyotrophic lateral sclerosis (ALS).

OBJECTIVE

Determine whether PB/TURSO prolonged tracheostomy/ventilation-free survival and/or reduced first hospitalisation in participants with ALS in the CENTAUR trial.

METHODS

Adults with El Escorial Definite ALS ≤18 months from symptom onset were randomised to PB/ TURSO or placebo for 6 months. Those completing randomised treatment could enrol in an open-label extension (OLE) phase and receive PB/TURSO for ≤30 months. Times to the following individual or combined key events were compared in the originally randomised treatment groups over a period spanning trial start through July 2020 (longest postrandomisation follow-up, 35 months): death, tracheostomy, permanent assisted ventilation (PAV) and first hospitalisation.

RESULTS

Risk of any key event was 47% lower in those originally randomised to PB/TURSO (n=87) versus placebo (n=48, 71% of whom received delayed-start PB/TURSO in the OLE phase) (HR=0.53; 95% CI 0.35 to 0.81; p=0.003). Risks of death or tracheostomy/PAV (HR=0.51; 95% CI 0.32 to 0.84; p=0.007) and first hospitalisation (HR=0.56; 95% CI 0.34 to 0.95; p=0.03) were also decreased in those originally randomised to PB/TURSO.

CONCLUSIONS

Early PB/TURSO prolonged tracheostomy/PAV-free survival and delayed first hospitalisation in ALS.

TRIAL REGISTRATION NUMBER

NCT03127514; NCT03488524.

Factors associated with Noninvasive ventilation compliance in patients with ALS/MND

Background: Although noninvasive ventilation (NIV) improves survival and quality of life (QOL) in ALS, use of NIV is suboptimal. Objective: To determine compliance with "early" NIV initiation, requisite for the feasibility of a large study of early NIV initiation, and examine factors impacting compliance. Methods: Seventy-three ALS participants with forced vital capacities (FVC) >50% were enrolled. Participants with FVC over 80% (Group 1) were initiated on NIV early (FVC between 80 and 85%). Participants with FVC between 50 and 80% (Group 2) started NIV at FVC between 50 and 55%. Symptom surveys, QOL scores, and NIV compliance (machine download documenting use ≥4 hours/night >60% of time) were collected following NIV initiation. Results: 53.6% of Group 1 and 50% of Group 2 were compliant 28 days following NIV initiation, with increased compliance over time. Participants who were unmarried, had lower income, lower educational attainment, or limited caregiver availability were less likely to be compliant. Bothersome symptoms in non-compliant participants included facial air pressure, frequent arousals with difficulty returning to sleep, and claustrophobia. Both compliant and noncompliant participants felt improved QOL with NIV; improvement was significantly greater in compliant participants. Conclusions: These data suggest ALS patients can comply with NIV early in their disease, and potentially benefit as evidenced by improved QOL scores, supporting both feasibility and need for a study comparing early versus late NIV initiation. Moreover, modifiable symptoms were identified that could be optimized to improve compliance. Further studies are needed to determine the impact of "early" intervention on survival and QOL.

Pulmonary function decline in amyotrophic lateral sclerosis

Background: There has been no comprehensive longitudinal study of pulmonary functions (PFTS) in ALS determining which measure is most sensitive to declines in respiratory muscle strength. Objective: To determine the longitudinal decline of PFTS in ALS and which measure supports Medicare criteria for NIV initiation first. Methods: Serial PFTs (maximum voluntary ventilation (MVV), maximum inspiratory pressure measured by mouth (MIP) or nasal sniff pressure (SNIP), maximum expiratory pressure (MEP), and Forced Vital Capacity (FVC)) were performed over 12 months on 73 ALS subjects to determine which measure showed the sentinel decline in pulmonary function. The rate of decline for each measure was determined as the median slope of the decrease over time. Medicare-based NIV initiation criteria were met if %FVC was ≤ 50% predicted or MIP was ≤ 60 cMH₂O. Results: 65 subjects with at least 3 visits were included for analyses. All median slopes were significantly different than zero. MEP and sitting FVC demonstrated the largest rate of decline. Seventy subjects were analyzed for NIV initiation criteria, 69 met MIP criteria first; 11 FVC and MIP criteria simultaneously and none FVC criteria first. Conclusions: MEP demonstrated a steeper decline compared to other measures suggesting expiratory muscle strength declines earliest and faster and the use of airway clearance interventions should be initiated early. When Medicare criteria for NIV initiation are considered, MIP criteria are met earliest. These results suggest that pressure-based measurements are important in assessing the timing of NIV and the use of pulmonary clearance interventions.

Use of a new ALS specific respiratory questionnaire: the ARES score

Objective: To develop an ALS respiratory symptom scale (ARES) and evaluate how ARES compares to Medical Research Council Modified Dyspnea Scale (MRC), Borg dyspnea scale, and respiratory subscores from ALSFRS-R (ALSFRS-Resp) in detecting respiratory symptoms, correlation with pulmonary function and ALSFRS-R, and deterioration of pulmonary function and ALSFRS-R over time.Methods: The ARES scale consists of 9 questions addressing dyspnea during activities and 3 questions addressing symptoms of worsening pulmonary function. 153 subjects with ALS completed MRC, Borg, ALSFRS-R, and ARES questionnaires at baseline, 16, 32, and 48 weeks, and spirometry at baseline. 73 of these subjects had spirometry, maximum inspiratory (MIP) and expiratory pressures (MEP), nasal inspiratory pressure (SNIP), and maximum voluntary ventilation (MVV) measured at each visit. Sensitivity of each scale and correlations between symptom scores, pulmonary function, and ALSFRS-R were evaluated at baseline and over the study duration.Results and conclusions: ARES was more sensitive than MRC, Borg and ALSFRS-Resp scales at baseline and for detecting changes at 16 and 32 weeks. ARES and ALSFRS-Resp correlated significantly with vital capacity at baseline, but Borg and MRC did not. Only ALSFRS-Resp correlated with respiratory pressures. Changes in ALSFRS-Resp and ARES both correlated with vital capacity decline; however, changes in ARES had superior correlation with respiratory pressure decline. Comparisons between telephone and in-person administration of ARES met criteria for satisfactory test-retest correlation in different settings one week apart. These findings suggest that the ARES may be more useful in monitoring symptom progression in ALS than other available scales.

Long-term survival of participants in the CENTAUR trial of sodium phenylbutyrate-taurursodiol in amyotrophic lateral sclerosis

An orally administered, fixed‐dose coformulation of sodium phenylbutyrate‐taurursodiol (PB‐TURSO) significantly slowed functional decline in a randomized, placebo‐controlled, phase 2 trial in ALS (CENTAUR). Herein we report results of a long‐term survival analysis of participants in CENTAUR. In CENTAUR, adults with ALS were randomized 2:1 to PB‐TURSO or placebo. Participants completing the 6‐month (24‐week) randomized phase were eligible to receive PB‐TURSO in the open‐label extension. An all‐cause mortality analysis (35‐month maximum follow‐up post‐randomization) incorporated all randomized participants. Participants and site investigators were blinded to treatment assignments through the duration of follow‐up of this analysis. Vital status was obtained for 135 of 137 participants originally randomized in CENTAUR. Median overall survival was 25.0 months among participants originally randomized to PB‐TURSO and 18.5 months among those originally randomized to placebo (hazard ratio, 0.56; 95% confidence interval, 0.34‐0.92; P = .023). Initiation of PB‐TURSO treatment at baseline resulted in a 6.5‐month longer median survival as compared with placebo. Combined with results from CENTAUR, these results suggest that PB‐TURSO has both functional and survival benefits in ALS.

Real-world evidence of riluzole effectiveness in treating amyotrophic lateral sclerosis

OBJECTIVE

To compare the effect of riluzole on median survival in population studies of patients with amyotrophic lateral sclerosis (ALS) with that observed in clinical trials. Methods: Two independent PubMed searches were conducted, to identify population studies that reported median survival for ALS patients who were either treated with riluzole or remained riluzole-free. Results: We identified 14 studies that met the inclusion criteria of reporting median survival and an additional study that reported mean survival of both riluzole and riluzole-free patients. Analysis of the 15 studies found that a majority reported increased survival of riluzole vs. riluzole-free patients. In 8 studies, the median survival for patients treated with riluzole was 6-19 months longer compared with patients not treated with riluzole (p < 0.05). Three additional studies reported a clinically meaningful treatment effect (range 3-5.9 months) but did not meet statistical significance. The remaining 4 studies did not show a meaningful treatment effect between riluzole and riluzole-free groups (<3 months), and differences among the groups were not significant. Also, 5 of the studies used multivariate regression analysis to investigate the level of association between treatment with riluzole and survival; these analyses supported the positive effect of riluzole on survival. Conclusions: A majority of population studies that compared riluzole vs. riluzole-free ALS patients found significant differences in median survival between the two groups, ranging from 6 to 19 months. This is substantially longer than the 2- to 3-month survival benefit observed in the pivotal clinical trials of riluzole.

Hereditary spastic paraplegia: gain-of-function mechanisms revealed by new transgenic mouse

Mutations of the SPAST gene, which encodes the microtubule-severing protein spastin, are the most common cause of hereditary spastic paraplegia (HSP). Haploinsufficiency is the prevalent opinion as to the mechanism of the disease, but gain-of-function toxicity of the mutant proteins is another possibility. Here, we report a new transgenic mouse (termed SPASTC448Y mouse) that is not haploinsufficient but expresses human spastin bearing the HSP pathogenic C448Y mutation. Expression of the mutant spastin was documented from fetus to adult, but gait defects reminiscent of HSP (not observed in spastin knockout mice) were adult onset, as is typical of human patients. Results of histological and tracer studies on the mouse are consistent with progressive dying back of corticospinal axons, which is characteristic of the disease. The C448Y-mutated spastin alters microtubule stability in a manner that is opposite to the expectations of haploinsufficiency. Neurons cultured from the mouse display deficits in organelle transport typical of axonal degenerative diseases, and these deficits were worsened by depletion of endogenous mouse spastin. These results on the SPASTC448Y mouse are consistent with a gain-of-function mechanism underlying HSP, with spastin haploinsufficiency exacerbating the toxicity of the mutant spastin proteins. These findings reveal the need for a different therapeutic approach than indicated by haploinsufficiency alone.

Genome-wide Analyses Identify KIF5A as a Novel ALS Gene

To identify novel genes associated with ALS, we undertook two lines of investigation. We carried out a genome-wide association study comparing 20,806 ALS cases and 59,804 controls. Independently, we performed a rare variant burden analysis comparing 1,138 index familial ALS cases and 19,494 controls. Through both approaches, we identified kinesin family member 5A (KIF5A) as a novel gene associated with ALS. Interestingly, mutations predominantly in the N-terminal motor domain of KIF5A are causative for two neurodegenerative diseases: hereditary spastic paraplegia (SPG10) and Charcot-Marie-Tooth type 2 (CMT2). In contrast, ALS-associated mutations are primarily located at the C-terminal cargo-binding tail domain and patients harboring loss-of-function mutations displayed an extended survival relative to typical ALS cases. Taken together, these results broaden the phenotype spectrum resulting from mutations in KIF5A and strengthen the role of cytoskeletal defects in the pathogenesis of ALS.

Genetic background effects on disease onset and lifespan of the mutant dynactin p150Glued mouse model of motor neuron disease

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease primarily affecting motor neurons in the central nervous system. Although most cases of ALS are sporadic, about 5–10% of cases are familial (FALS) with approximately 20% of FALS caused by mutations in the Cu/Zn superoxide dismutase (SOD1) gene. We have reported that hSOD1-G93A transgenic mice modeling this disease show a more severe phenotype when the transgene is bred on a pure SJL background and a milder phenotype when bred on a pure B6 background and that these phenotype differences link to a region on mouse Chromosome 17.To examine whether other models of motor neuron degeneration are affected by genetic background, we bred the mutant human dynactin p150^Glued (G59S-hDCTN1) transgene onto inbred SJL and B6 congenic lines. This model is based on an autosomal dominant lower motor neuron disease in humans linked to a mutation in the p150^Glued subunit of the dynactin complex. As seen in hSOD1-G93A mice, we observed a more severe phenotype with earlier disease onset (p<0.001) and decreased survival (p<0.00001) when the G59S-hDCTN1 transgene was bred onto the SJL background and delayed onset (p<0.0001) with increased survival (p<0.00001) when bred onto the B6 background. Furthermore, B6 mice with an SJL derived chromosome 17 interval previously shown to delay disease onset in hSOD1-G93A mice also showed delays onset in G59S-hDCTN1 mice suggesting that at least some genetic modifiers are shared. We have shown that genetic background influences phenotype in G59S-hDCTN1 mice, in part through a region of chromosome 17 similar to the G93-hSOD1 ALS mouse model. These results support the presence of genetic modifiers in both these models some of which may be shared. Identification of these modifiers will highlight intracellular pathways involved in motor neuron disease and provide new therapeutic targets that may be applicable to motor neuron degeneration.

Mutation in the novel nuclear-encoded mitochondrial protein CHCHD10 in a family with autosomal dominant mitochondrial myopathy

Mitochondrial myopathies belong to a larger group of systemic diseases caused by morphological or biochemical abnormalities of mitochondria. Mitochondrial disorders can be caused by mutations in either the mitochondrial or nuclear genome. Only 5% of all mitochondrial disorders are autosomal dominant. We analyzed DNA from members of the previously reported Puerto Rican kindred with an autosomal dominant mitochondrial myopathy (Heimann-Patterson et al. 1997). Linkage analysis suggested a putative locus on the pericentric region of the long arm of chromosome 22 (22q11). Using the tools of integrative genomics, we established chromosome 22 open reading frame 16 (C22orf16) (later designated as CHCHD10) as the only high-scoring mitochondrial candidate gene in our minimal candidate region. Sequence analysis revealed a double-missense mutation (R15S and G58R) in cis in CHCHD10 which encodes a coiled coil-helix-coiled coil-helix protein of unknown function. These two mutations completely co-segregated with the disease phenotype and were absent in 1,481 Caucasian and 80 Hispanic (including 32 Puerto Rican) controls. Expression profiling showed that CHCHD10 is enriched in skeletal muscle. Mitochondrial localization of the CHCHD10 protein was confirmed using immunofluorescence in cells expressing either wild-type or mutant CHCHD10. We found that the expression of the G58R, but not the R15S, mutation induced mitochondrial fragmentation. Our findings identify a novel gene causing mitochondrial myopathy, thereby expanding the spectrum of mitochondrial myopathies caused by nuclear genes. Our findings also suggest a role for CHCHD10 in the morphologic remodeling of the mitochondria.

A major QTL on mouse chromosome 17 resulting in lifespan variability in SOD1-G93A transgenic mouse models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a late-onset degenerative disease affecting motor neurons in the spinal cord, brainstem, and motor cortex. There is great variation in the expression of ALS symptoms even between siblings who both carry the same Cu/Zn superoxide dismutase (SOD1) mutations. One important use of transgenic mouse models of SOD1-ALS is the study of genetic influences on ALS severity. We utilized multiple inbred mouse strains containing the SOD1-G93A transgene to demonstrate a major quantitative trait locus (QTL) on mouse chromosome 17 resulting in a significant shift in lifespan. Reciprocal crosses between long- and short-lived strains identified critical regions, and we have narrowed the area for potential genetic modifier(s) to < 2Mb of the genome. Results showed that resequencing of this region resulted in 28 candidate genes with potentially functional differences between strains. In conclusion, these studies provide the first major modifier locus affecting lifespan in this model of FALS and, once identified, these candidate modifier genes may provide insight into modifiers of human disease and, most importantly, define new targets for the development of therapies.

Phenotype of transgenic mice carrying a very low copy number of the mutant human G93A superoxide dismutase-1 gene associated with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease of the motor neuron. While most cases of ALS are sporadic, 10% are familial (FALS) with 20% of FALS caused by a mutation in the gene that codes for the enzyme Cu/Zn superoxide dismutase (SOD1). There is variability in sporadic ALS as well as FALS where even within the same family some siblings with the same mutation do not manifest disease. A transgenic (Tg) mouse model of FALS containing 25 copies of the mutant human SOD1 gene demonstrates motor neuron pathology and progressive weakness similar to ALS patients, leading to death at approximately 130 days. The onset of symptoms and survival of these transgenic mice are directly related to the number of copies of the mutant gene. We report the phenotype of a very low expressing (VLE) G93A SOD1 Tg carrying only 4 copies of the mutant G93ASOD1 gene. While weakness can start at 9 months, only 74% of mice 18 months or older demonstrate disease. The VLE mice show decreased motor neurons compared to wild-type mice as well as increased cytoplasmic translocation of TDP-43. In contrast to the standard G93A SOD1 Tg mouse which always develops motor weakness leading to death, not all VLE animals manifested clinical disease or shortened life span. In fact, approximately 20% of mice older than 24 months had no motor symptoms and only 18% of VLE mice older than 22 months reached end stage. Given the variable penetrance of clinical phenotype, prolonged survival, and protracted loss of motor neurons the VLE mouse provides a new tool that closely mimics human ALS. This tool will allow the study of pathologic events over time as well as the study of genetic and environmental modifiers that may not be causative, but can exacerbate or accelerate motor neuron disease.

Effect of genetic background on phenotype variability in transgenic mouse models of amyotrophic lateral sclerosis: a window of opportunity in the search for genetic modifiers

Transgenic (Tg) mouse models of FALS containing mutant human SOD1 genes (G37R, G85R, D90A, or G93A missense mutations or truncated SOD1) exhibit progressive neurodegeneration of the motor system that bears a striking resemblance to ALS, both clinically and pathologically. The most utilized and best characterized Tg mice are the G93A mutant hSOD1 (Tg(hSOD1-G93A)1GUR mice), abbreviated G93A. In this review we highlight what is known about background-dependent differences in disease phenotype in transgenic mice that carry mutated human or mouse SOD1. Expression of G93A-hSOD1Tg in congenic lines with ALR, NOD.Rag1KO, SJL or C3H backgrounds show a more severe phenotype than in the mixed (B6xSJL) hSOD1Tg mice, whereas a milder phenotype is observed in B6, B10, BALB/c and DBA inbred lines. We hypothesize that the background differences are due to disease-modifying genes. Identification of modifier genes can highlight intracellular pathways already suspected to be involved in motor neuron degeneration; it may also point to new pathways and processes that have not yet been considered. Most importantly, identified modifier genes provide new targets for the development of therapies.

The ALSSQOL: balancing physical and nonphysical factors in assessing quality of life in ALS

BACKGROUND

There is no generally accepted instrument for measuring quality of life (QOL) in patients with ALS. Current instruments are either too heavily weighted toward strength and physical function or useful for the evaluation of individuals but of less utility in assessing large samples.

OBJECTIVE

To develop and evaluate the psychometric properties of an ALS-specific QOL instrument (the ALSSQOL) that would reflect overall QOL as assessed by the patient and would be valid and reliable across large samples.

METHODS

The ALSSQOL is based on the McGill Quality of Life Questionnaire (MQOL), modified by changes in format and by adding questions on religiousness and spirituality, items derived from interviews with ALS patients, and items identified from open-ended questions administered during the MQOL. The psychometric properties of the ALSSQOL were assessed by a prospective multicenter study in which participants completed the ALSSQOL, other instruments measuring overall QOL, and instruments assessing religiousness, spirituality, and psychological distress.

RESULTS

A 59-item ALSSQOL was developed; 342 patients evaluated its psychometric properties. Completion time averaged 15 minutes. Forty-six items loaded on six factors. The ALSSQOL demonstrated concurrent, convergent, and discriminant validity for the overall instrument and convergent validity for its subscales. Analysis of individual items permitted insight into variables of clinical importance.

CONCLUSIONS

This new ALS-specific quality of life instrument is a practical tool for the assessment of overall quality of life in individuals with ALS and appears to be valid and useful across large samples. Validation studies of a shortened version are now under way.

Background and gender effects on survival in the TgN(SOD1-G93A)1Gur mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is a progressive neuromuscular disorder. While most cases of ALS are sporadic, 10-15% are familial, and of these 15-20% possess a mutation in the gene that codes for the enzyme Cu/Zn superoxide dismutase (SOD1). In families of ALS patients with specific SOD1 mutations, affected members demonstrate significant heterogeneity of disease and a large variation in age of onset and severity, suggesting that there are genetic modifiers of disease expression. Transgenic mice expressing mutant forms of SOD1 demonstrate symptoms similar to those seen in patients with ALS. We have observed in our colony of G93A SOD1 transgenic mice a milder phenotype in mice in a C57BL/6J background than the C57BL/6JxSJL/J hybrid background used by Jackson Laboratories to maintain their colony. To investigate the effect of genetic background on phenotype, we have constructed congenic lines on two genetic backgrounds, C57BL/6J (B6) and SJL/J (SJL). We report the influence of background and gender on the survival of these congenic lines compared to the hybrid C57BL/6JxSJL/J background. The mean survival of G93A SOD1 mice in the hybrid B6/SJL background was 130 days, with females surviving significantly longer than males. When compared to the hybrid B6/SJL background, the survival of mice in the SJL background significantly decreased, and the gender difference in survival was maintained. On the other hand, mean survival in the B6 background significantly increased, and in contrast to the B6/SJL and SJL backgrounds, there was no difference in survival between males and females. Transgene copy numbers were verified in all animals to ensure that any phenotypic differences observed were not due to alterations in copy number. This is the first report of a shortened lifespan when the G93A SOD1 transgene is placed on the SJL/J background and an increased survival with the loss of gender influences when the transgene is placed on the C57BL/6J background.

Effect of transgene copy number on survival in the G93A SOD1 transgenic mouse model of ALS

Transgenic mice expressing multiple copies of the G93A mutant form of SOD1 develop motor neuron pathology and clinical symptoms similar to those seen in patients with amyotrophic lateral sclerosis (ALS). The phenotype of these mice is dependent on the number of transgene copies in their genome. Changes in transgene copy number, although rare, can sometimes occur while mating due to intra locus recombination events during meiosis. The objective of this study was to develop a real time quantitative PCR method to determine changes in transgene copy number in these mice and to evaluate the effect of transgene copy number on the phenotype of the G93A SOD1 mouse model of ALS.

A randomized, placebo-controlled trial of topiramate in amyotrophic lateral sclerosis

OBJECTIVE

To determine if long-term topiramate therapy is safe and slows disease progression in patients with ALS.

METHODS

A double-blind, placebo-controlled, multicenter randomized clinical trial was conducted. Participants with ALS (n = 296) were randomized (2:1) to receive topiramate (maximum tolerated dose up to 800 mg/day) or placebo for 12 months. The primary outcome measure was the rate of change in upper extremity motor function as measured by the maximum voluntary isometric contraction (MVIC) strength of eight arm muscle groups. Secondary endpoints included safety and the rate of decline of forced vital capacity (FVC), grip strength, ALS functional rating scale (ALSFRS), and survival.

RESULTS

Patients treated with topiramate showed a faster decrease in arm strength (33.3%) during 12 months (0.0997 vs 0.0748 unit decline/month, p = 0.012). Topiramate did not significantly alter the decline in FVC and ALSFRS or affect survival. Topiramate was associated with an increased frequency of anorexia, depression, diarrhea, ecchymosis, nausea, kidney calculus, paresthesia, taste perversion, thinking abnormalities, weight loss, and abnormal blood clotting (pulmonary embolism and deep venous thrombosis).

CONCLUSIONS

At the dose studied, topiramate did not have a beneficial effect for patients with ALS. High-dose topiramate treatment was associated with a faster rate of decline in muscle strength as measured by MVIC and with an increased risk for several adverse events in patients with ALS. Given the lack of efficacy and large number of adverse effects, further studies of topiramate at a dose of 800 mg or maximum tolerated dose up to 800 mg/day are not warranted.

GLT-1 glutamate transporter levels are unchanged in mice expressing G93A human mutant SOD1

A decrease in expression of the glutamate transporter GLT-1 is thought to be responsible for the increase in extracellular glutamate observed in patients with amyotrophic lateral sclerosis (ALS) and in a transgenic mouse model of ALS. We examined protein levels of the glutamate transporters GLT-1, GLAST and EAAC1 in the G93A (SOD1) transgenic mouse model of ALS. GLT-1 was detected in two bands (72 and 150 kD). Semi-quantitative analysis of Western blots showed that GLT-1 levels in sensorimotor cortex, brain stem, and cervical and lumbar spinal cord of G93A mice did not differ significantly from controls, either at end stage or at 60- or 90-days old. Nevertheless, other differences were found in GLT-1 at end stage. The percentage of total GLT-1 in the 150 kD band increased significantly (p<0.05) in the spinal cord and was elevated in the brain stem and cortex. Furthermore, brain stem and spinal cord GLT-1 from G93A mice showed retarded mobility on gels compared to controls (M(r) approximately equal to 77.3+/-2.3 and 164.3+/-3.1 vs. 72.2+/-2.4 and 153.6+/-4.7, respectively). GLAST and EAAC1 were unchanged in both amount and mobility. These results show that a loss of GLT-1 protein is not necessary for ALS-like neurodegeneration in G93A mice. However, the changes in GLT-1 mobility and distribution indicate that GLT-1 is altered in mice with the SOD1 mutation.

Patch clamp studies of the thr1313met mutant sodium channel causing paramyotonia congenita

Paramyotonia congenita (PC) is an autosomal-dominant disorder due to a point mutation in the adult skeletal muscle Na channel gene. Muscle fibers from PC patients have normal membrane properties at 32 degrees C. At 27 degrees C, they are inexcitable, have increased Na conductance, and have a reduced resting membrane potential of -40 mV. To define the biophysical basis for the muscle membrane abnormalities, we performed patch clamp whole-cell and outside-out single Na channel studies at 22 degrees C on cultured human muscle cells from 4 control patients and 2 sisters with PC and the thr1313met mutant Na channel. The whole-cell studies showed no difference in window currents. Unlike cells transfected with the thr1313met mutant Na channel, the inactivation time constant, tau(h), for PC cells was similar to control cells. For PC recordings containing long-duration single Na channel openings, mean open time was prolonged at -60, -40, and -20 mV. The long-duration Na channel openings occurred randomly with no evidence of modal gating. The number of channel openings, occurrence of late openings, and the prolonged mean open time resulted in a sustained inward Na current at -40 mV. We suggest that the biophysical marker of the thr1313met mutant Na channel is a voltage- and temperature-dependent abnormality in mutant single Na channel behavior.

Elevated cortical extracellular fluid glutamate in transgenic mice expressing human mutant (G93A) Cu/Zn superoxide dismutase

Transgenic mice expressing a mutated (G93A) human Cu/Zn superoxide dismutase (SOD1) develop motor neuron pathology and clinical symptoms similar to those seen in patients with amyotrophic lateral sclerosis. Loss of motor neurons is most prominent in lumbar, followed by cervical cord and then brainstem. No significant cell death has been reported in motor cortex. The integrity of the cortical glutamate reuptake systems was evaluated using intracerebral microdialysis and western immunoblot assays for the glutamate transporters GLT-1, GLAST, and EAAC1. The basal extracellular fluid levels of aspartate, glutamate, glutamine, 3,4-dihydroxyphenylacetic acid, and 5-hydroxyindole-3-acetic acid were evaluated by HPLC. The extraction fraction of L-3H]glutamate, corrected with [14C]mannitol, was also evaluated. GLT-1, EAAC1, and GLAST protein levels were determined by semiquantitative chemiluminescence immunoblot of proteins from membrane-enriched fractions. The relative optical density of film was translated into relative protein level by comparison with a standard control mouse. The SOD1 mutant mice demonstrated a significant (p < 0.05) increase in basal levels of extracellular aspartate and glutamate. In addition, when the glutamate extraction fraction was challenged with exogenous unlabeled glutamate (500 microM) by reversed microdialysis, the glutamate extraction fraction in the mutant SOD1 mice was decreased significantly from control levels. The SOD1 mutant mice demonstrated no difference in the cortical protein levels of the glutamate transporter subtypes. This study demonstrates that in areas of no visible pathology and no loss of glutamate transporter proteins, SOD1 mutant mice have elevated extracellular fluid aspartate and glutamate levels and a decreased capacity to clear glutamate from the extracellular space.

Biochemical and genetic studies in a family with mitochondrial myopathy

We present a family with severe exercise intolerance, progressive proximal weakness, and lactic acidemia. Fifteen of 24 family members in five generations were affected. Since the affected males do not have offspring at this time, the family pedigree is consistent with either maternal or autosomal dominant inheritance. Muscle histochemistry showed ragged-red fibers and electron microscopy showed globular mitochondrial inclusions. Biochemical analysis showed reduced muscle activities of mitochondrial NADH-cytochrome c reductase (1 of 2 patients), succinate-cytochrome c reductase (2 patients), and cytochrome c oxidase (2 patients). For 1 patient, sequence analysis of 44% of the muscle mitochondrial DNA including all 22 transfer RNA regions showed no point mutation with pathogenic significance. Southern blot analysis showed no deletion. Six affected members of the family were treated with methylprednisolone (0.25 mg/kg) for 3 months. Muscle strength, serum lactate, and energy metabolism at rest (measured by 31P magnetic resonance spectroscopy) significantly improved with treatment.

Neuroleptic malignant syndrome and malignant hyperthermia. Important issues for the medical consultant

Neuroleptic malignant syndrome and malignant hyperthermia share two cardinal clinical features: hypothermia and rigidity. Both syndromes can result in rhabdomyolysis and have high mortality rates if left untreated. This article reviews each syndrome and its pathogenesis and treatment.

Modulation of Ca2+ release and Na+ channel function in skeletal muscle by fatty acids

Ca(2+)- and halothane-induced Ca(2+) release and Na+ currents are modulated by free fatty acids (FAs). FA modulation of ion currents may have important implications for general muscle physiology and skeletal muscle disorders, including malignant hyperthermia (MH).

Clinical and electrophysiological assessments in ALS patients

Since the relationships between traditional assessments in ALS patients have not been defined, three clinical and four electrophysiological assessments were performed in a cross-sectional study of 87 ALS patients. The clinical assessments produced Norris ALS scores, muscle strength scores and illness durations (DUR). The electrophysiological assessments produced scores for motor unit interference pattern, denervation potentials, compound muscle action potential, and fasciculations. The individual muscle scores were averaged to produce mean scores, and Spearman rank correlations were performed on the mean scores. The association between Norris ALS and mean muscle strength (MMS) scores is significant (p less than .001, rs = 0.84), and these scores are significantly correlated with mean interference pattern (0.77, 0.82), mean denervation potential (-0.63, -0.70), and mean compound muscle action potential scores (0.55, 0.60), respectively. Correlations between IP and DP scores (-0.71), IP and CMAP scores (0.62), and DP and CMAP (-0.56) scores are also significant. Scatterplots of the data and regression lines suggest linear relationships between each of these assessments. Illness duration and fasciculation scores are not strongly correlated (rs less than 0.55) with any of the other clinical or electrophysiological assessments.

Cramp-fasciculation syndrome: a treatable hyperexcitable peripheral nerve disorder

We report nine patients with muscle aching, cramps, stiffness, exercise intolerance, and peripheral nerve hyperexcitability. Neurologic examination showed calf fasciculations in seven, quadriceps myokymia in two, and deltoid myokymia in one patient. Two patients had mild increase in serum creatine kinase. Muscle biopsy showed either no abnormality (three patients) or mild neurogenic changes (four patients). Fasciculations were the only abnormality on routine electrodiagnostic studies. Supramaximal stimulation of the median, ulnar, peroneal, and posterior tibial nerves at frequencies of 0.5, 1, 2, and 5 Hz produced showers of electrical potentials following the M response in at least one nerve. In three patients, the fasciculations and evoked electrical potentials were abolished by regional application of curare but not nerve block. Carbamazepine therapy caused moderate-to-marked reduction of symptoms and nerve hyperexcitability. We designate this hyperexcitable peripheral nerve disorder as the "cramp-fasciculation syndrome."

Factors influencing outcome of prednisone dose reduction in myasthenia gravis

We reviewed retrospectively 114 prednisone dose reduction attempts in 63 myasthenic patients. Dose reduction was considered successful if a patient remained asymptomatic for more than 1 year on no prednisone or a stable low dose of prednisone. Successful dose reduction attempts were more common in patients taking azathioprine, but thymectomy did not influence taper outcome. Slower rate of dose reduction and higher ending dose of prednisone improved the chance of success.

Peripheral neuropathy associated with eosinophilia-myalgia syndrome

In 1989, the Centers for Disease Control recognized the existence of an epidemic illness characterized by myalgia and eosinophilia in individuals taking preparations containing L-tryptophan. We evaluated 3 patients with eosinophilia-myalgia syndrome who presented with subacute progressive neuropathies. The neuropathies were predominantly motor and maximal in the lower extremities. Two patients were confined to a wheelchair and one was ventilator-dependent and bedridden. Sensory loss predominantly involved small fiber modalities. Electrophysiological studies showed multifocal marked conduction slowing and conduction block indicating segmental demyelination, with associated axonal degeneration that was accentuated distally. Examination of sural nerve biopsy specimens demonstrated axonal degeneration in all 3 patients and perivascular infiltrates in 2. Levels of quinolinic acid, a neurotoxic metabolite of L-tryptophan, were elevated in the cerebrospinal fluid in the 2 patients in whom it was measured. The cause of the neuropathy is unknown but may include immune mechanisms or toxicity of eosinophils, L-tryptophan, its metabolic products, or contaminants within L-tryptophan preparations.

Halothane-caffeine contracture testing in neuromuscular diseases

The association of malignant hyperthermia (MH) with neuromuscular disorders has been recognized since 1970. These disorders include central core disease, Duchenne muscular dystrophy, myotonia congenita, myotonic dystrophy, nonspecific myopathies, and King-Denborough syndrome. In order to assess the anesthetic risk of MH in the neuromuscular population, we performed halothane and caffeine contracture testing for MH susceptibility on biopsied muscle removed from 25 consecutive neuromuscular patients during diagnostic evaluation. Positive contracture tests were found in 7 of 18 patients with myopathic disorders and 3 of 7 patients with neurogenic disorders. Two of our patients had anesthetic events suggesting MH. These findings suggest that myopathic and neuropathic disorders share pathogenic mechanisms with MH, resulting in positive contracture tests and possibly leading to clinical events during anesthesia. Although there is controversy regarding the interpretation of a positive contracture test, contracture testing remains the most widely accepted test for MH susceptibility. Thus, a variety of neuromuscular disorders may be associated with MH susceptibility, and caution should be exercised during anesthesia in this group of patients.

Malignant hyperthermia susceptibility in neuroleptic malignant syndrome

The relationship between neuroleptic malignant syndrome (NMS) and malignant hyperthermia (MH) was investigated using the in vitro skeletal muscle contracture test to screen for MH-susceptibility in NMS patients. The maximum contracture tension which developed following exposure to halothane (1-3%), and incremental doses of fluphenazine (0.2-25.6 mM) was measured in muscle obtained from seven NMS, six MH, and six control patients. Comparison of the cumulative responses to fluphenazine revealed no significant differences among the groups. However, the response (mean +/- SEM) to halothane in the NMS group (1.7 +/- 0.7 g), which was similar to the response in the MH group (1.5 +/- 0.2 g), was significantly greater than the response found in controls (0.2 +/- 0.1 g). In addition, five of seven NMS patients could be diagnosed as MH-susceptible, based on the development of muscle contractures greater than 0.7 g in response to 1-3% halothane. In contrast, none of the controls were MH-susceptible. These findings appear to correlate with clinical evidence suggesting an association between NMS and MH.

Malignant hyperthermia susceptibility in X-linked muscle dystrophies

To evaluate malignant hyperthermia (MH) susceptibility in X-linked muscular dystrophies, halothane and caffeine contracture tests were performed on muscle fiber bundles from five patients with Duchenne muscular dystrophy (DMD) and two patients with Becker muscular dystrophy (BMD). Two DMD patients and one BMD patient had positive contracture tests. Since a positive contracture test is currently the best indicator of anesthetic susceptibility in the MH population, and episodes of MH in dystrophic patients have been reported, patients with DMD and BMD may be at risk for developing similar anesthetic complications. Awareness of this potential anesthetic risk is of importance because orthopedic interventions are increasingly more common in these patients.

King-Denborough syndrome: contracture testing and literature review

The King-Denborough syndrome (KDS) is characterized by dysmorphic features, myopathy, and malignant hyperthermia (MH). Physiologic contracture testing for MH susceptibility has not been reported in KDS. A young boy with KDS underwent muscle biopsy evaluation at age 3 years that documented an abnormal contracture response to halothane, indicating MH susceptibility. Histopathology demonstrated small type II fibers associated with type I hypertrophy. Contracture testing of muscle obtained from the patient's mother was positive, while a sibling's test was negative. This case is the first to demonstrate susceptibility to MH with KDS by using physiologic contracture testing. The presence of positive MH results in both the patient and his mother suggest one of the following: (1) KDS may be part of the spectrum of autosomal dominantly inherited MH; (2) the locus for MH and for KDS may be linked closely and inherited concurrently, or; (3) the association of MH and KDS may be coincidental.

Morphological changes in the cochlear nuclear complex in primate phylogeny and development

The primate cochlear nuclear complex exhibits several characteristic morphological differences in the various primate families from Lorisidae through Hominidae. The most striking differences occur in the organization of the dorsal cochlear nucleus in which the laminar pattern becomes progressively obscured. Granule cells form an external granular layer as well as being intermixed within the molecular and pyramidal layers in slow lorises and squirrel and rhesus monkeys. Whereas a prominent external granular layer remains in chimpanzees, granule cells are scant in other portions of the nucleus. Human adults lack an external granular layer. A small number of granule cells occur but with inconstant distribution. Primates lack the linear array of pyramidal cells oriented perpendicularly to the epithelial surface as seen in cats. The granule cell layer exhibits similar regression in development of the human cochlear complex. The external granular layer is prominent in the fetus but rapidly decreases in size after birth. It achieves its adult form prior to 18 months. The data suggest that neuronal attrition, or programmed cell death, may be the major mechanism accounting for the alterations that occur in the human granule cell layer. Other differences in cytoarchitecture, within the great apes and humans, include decreases in the small and giant cell populations of the cochlear complex. These changes, in consort with the organizational changes and reduction of granule cells as noted above, suggest a trend towards reduced intranuclear integration at the level of the cochlear nucleus coupled with encephalization of the auditory system.

Neuroleptic malignant syndrome. Patient with unique clinical and physiologic features

Lethargy, marked muscle weakness and rigidity, a maximal temperature of 40 degrees C, and a maximal creatine kinase value of 17,240 IU/liter developed in a 36-year-old woman following treatment with several neuroleptics. Initial treatment with dantrolene was unsuccessful. The patient's condition improved gradually over a 10-day period with no specific therapy. Muscle biopsy revealed a contracture pattern diagnostic of malignant hyperthermia susceptibility, as well as abnormal sensitivity to fluphenazine. This report may be the first description of a patient with neuroleptic malignant syndrome in whom muscle biopsy response similar to that seen in malignant hyperthermia occurred and documents that dantrolene is not uniformly successful therapy for this syndrome.