Natural history of MELAS associated with mitochondrial DNA m.3243A>G genotype

OBJECTIVE

To describe the natural history of clinical and laboratory features associated with the m.3243A>G mitochondrial DNA point mutation. Natural history data are needed to obtain prognostic information and for clinical trial planning.

METHODS

We included 85 matrilineal relatives from 35 families with at least 2 visits in this prospective cohort study. Thirty-one were fully symptomatic with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), and 54 were carrier relatives. Evaluations included standardized questionnaires (medical history and daily living functioning), physical examination, neuropsychological testing, and a battery of imaging and laboratory tests. We evaluated changes in clinical and laboratory features over time and survival. Outcomes are reported over a follow-up period of up to 10.6 years (mean 3.8 ± 2.2 years for patients and 5.5 ± 3.0 for carrier relatives).

RESULTS

Neurologic examination, neuropsychological testing, and daily living scores significantly declined in all patients with MELAS, whereas no significant deterioration occurred in carrier relatives. Cerebral MRI scores declined significantly in patients with MELAS. Magnetic resonance spectroscopy estimates of lactate in the lateral ventricles increased over time, and high lactate was associated with increased mortality. Symptom onset in childhood often was associated with worse outcome. Patients with MELAS had a greater death rate than carrier relatives.

CONCLUSIONS

Patients with MELAS carrying the m.3243A>G mutation show a measurable decline in clinical and imaging outcomes. It is hoped that these data will be helpful in anticipating the disease course and in planning clinical trials for MELAS.

Six-Minute Walk Test demonstrates motor fatigue in spinal muscular atrophy

BACKGROUND

In spinal muscular atrophy (SMA), weakness, decreased endurance, and fatigue limit mobility. Scales have been developed to measure function across the wide spectrum of disease severity. However, these scales typically are observer dependent, and scores are based on sums across Likert-scaled items. The Six-Minute Walk Test (6MWT) is an objective, easily administered, and standardized evaluation of functional exercise capacity that has been proven reliable in other neurologic disorders and in children.

METHODS

To study the performance of the 6MWT in SMA, 18 ambulatory participants were evaluated in a cross-sectional study. Clinical measures were 6MWT, 10-m walk/run, Hammersmith Functional Motor Scale-Expanded (HFMSE), forced vital capacity, and handheld dynamometry. Associations between the 6MWT total distance and other outcomes were analyzed using Spearman correlation coefficients. A paired t test was used to compare the mean distance walked in the first and sixth minutes.

RESULTS

The 6MWT was associated with the HFMSE score (r = 0.83, p < 0.0001), 10-m walk/run (r = -0.87, p < 0.0001), and knee flexor strength (r = 0.62, p = 0.01). Gait velocity decreased during successive minutes in nearly all participants. The average first minute distance (57.5 m) was significantly more than the sixth minute distance (48 m) (p = 0.0003).

CONCLUSION

The Six-Minute Walk Test (6MWT) can be safely performed in ambulatory patients with spinal muscular atrophy (SMA), correlates with established outcome measures, and is sensitive to fatigue-related changes. The 6MWT is a promising candidate outcome measure for clinical trials in ambulatory subjects with SMA.

Placental structure: in a comparative aspect

The outstanding structural diversity of the placenta among mammals, i.e. horse, pig, domestic ruminants, cat. Guinea pig and human, has been studied in a comparative manner using terms of classification such as: type of placental membranes, placental shape, placental maternofetal interdigitation, layers of the placental interhemal barrier, trophoblast invasiveness and decidual cell reaction, formation of syncytiotrophoblast, maternofetal blood flow interrelationships, and placental separation at birth. These terms, originating partly from classical acquirements of knowledge and partly from recent research, are presented and new aspects discussed; thus helping towards a better understanding of the structure and function of the different placental types.

Deriving turbulence characteristics from the COSMO numerical weather prediction model for dispersion applications

Abstract. At MeteoSwiss an integrated modelling system is used to simulate the dispersion of radioactive material in emergency situations. For the prediction of the atmospheric flow, the COSMO numerical weather prediction model is used. The model is run operationally at 6.6 and 2.2 km horizontal resolution, respectively and uses a 1.5 order turbulence closure with a prognostic equation for turbulent kinetic energy. Both versions of the COSMO model are coupled off-line with a Lagrangian particle dispersion model (LPDM). The aim of this study is to investigate the sensitivity of the dispersion model to different interfacing approaches between LPDM and the COSMO model. The diagnosed turbulence variables are validated on an ideal convective case and two measurement campaigns. Simulations of hypothetical pollutant releases show that the different interfacing approaches can lead to substantial changes in the forecasted concentrations.

Hyperbaric Oxygenation in the Treatment of Life-Threatening Isobutyl Nitrite-Induced Methemoglobinemia—A Case Report

Methemoglobinemia usually results from exposure to oxidizing substances such as nitrates or nitrites. Iron within hemoglobin is oxidized from the ferrous (Fe2+) state to the ferric (Fe3+) state, resulting in the inability to transport oxygen and carbon dioxide. Clinically, this condition causes functional cyanosis. As methemoglobin levels increase, patients show evidence of cellular hypoxia in all tissues. Death usually occurs when methemoglobin fractions approach 70% of total hemoglobin. We describe the case of a 35-year-old female patient with severe life-threatening isobutyl nitrite-induced methemoglobinemia of 75% of total hemoglobin. Toluidine-blue was administered as first-line antidotal therapy immediately, followed by hyperbaric oxygenation. The patient recovered uneventfully and could be discharged 3 days later.

Historical underpinnings of the term essential tremor in the late 19th century

BACKGROUND

The term essential tremor has been in regular use since the second half of the 20th century. To modern neurologists, the word "essential" may seem cryptic. The historical underpinnings of this term have not been examined.

OBJECTIVES

To bring to attention early medical reports using the term essential tremor and examine the characteristics of the disorder that contributed to the proposed use of the term.

METHODS

Review of 19th and early 20th century medical literature on essential tremor.

RESULTS

The term tremore semplice essenziale (simple essential tremor) was first used by Burresi (Italy, 1874) to describe an 18-year-old man with severe, isolated action tremor. Several years later, Maragliano (Italy, 1879), Nagy (Austria, 1890), and Raymond (France, 1892) described similar cases and proposed the terms tremore essenziale congenito (essential congenital tremor), essentieller Tremor (essential tremor), and tremblement essentiel héréditaire (hereditary essential tremor) to define the illness. Mirroring contemporaneous views of constitutional and inherited disease, the key ingredients of the disorder were viewed as the constant presence of tremor in the absence of other neurologic signs and its heritable nature. By the early 20th century, the term began to appear in the medical literature with greater frequency.

CONCLUSIONS

Toward the end of the 19th century, several clinicians attempted to provide a nosologic separation for a tremor diathesis that was often familial and occurred in isolation of other neurologic signs. This disorder, which was termed essential tremor, was later recognized as one of the most common neurologic disorders.

The changing natural history of spinal muscular atrophy type 1

BACKGROUND

Noninvasive ventilation has become increasingly available to spinal muscular atrophy (SMA) patients since the early 1990 s. This is expected to have improved survival for SMA type 1 patients.

OBJECTIVE

To assess whether there has been a change in survival in patients with SMA type 1 between 1980 and 2006.

METHODS

We used deidentified, family-reported data from participants in the International Spinal Muscular Atrophy Patient Registry and obtained additional clinical information through a mail-in questionnaire. One hundred forty-three patients with SMA type 1 were included in the analysis. Survival of patients born in 1995-2006 (n = 78) was compared with that of patients born in 1980-1994 (n = 65), using the Kaplan-Meier method and Cox proportional hazards models with age at death as the outcome.

RESULTS

Patients born in 1995 though 2006 had significantly increased survival compared with those born in 1980-1994 (log-rank test, p < 0.001). In a Cox model, patients born in 1995-2006 had a 70% reduction in the risk of death compared with those born in 1980-1994 (hazard ratio [HR] 0.3, 95% CI 0.2-0.5, p < 0.001) over a mean follow-up of 49.9 months (SD 61.1, median 22.0). However, when controlling for demographic and clinical care variables, year of birth was no longer significantly associated with age at death (HR 1.0, 95% CI 0.6-1.8, p = 0.9), whereas ventilation for more than 16 h/d, use of a mechanical insufflation-exsufflation device, and gastrostomy tube feeding showed a significant effect in reducing the risk of death.

CONCLUSION

Survival in spinal muscular atrophy type 1 patients has increased in recent years, in relation to the growing trend toward more proactive clinical care.

Caviomorph placentation as a model for trophoblast invasion

The guinea pig and its relatives are promising candidates as animal models for studying trophoblast invasion. The origin, migration routes and kinetics of invasive trophoblast cells were examined in two caviomorph species. Histology and immunohistochemistry were done on placentas from 38 guinea pigs of days 20-47 and 13 degus of days 25-51 of gestation. BrdU was used as an in vivo marker for proliferation and for tracing of migration routes in the placenta; it was injected 24h to 15 days before collecting the material. In both species extravillous-like trophoblast cells are derived from proliferating stem cell aggregations in the subplacenta, which are comparable to the cell columns in humans. Migration routes and kinetics under in vivo conditions revealed a mean invasive depth of 300-350 microm/day and a mean life span of the extravillous-like trophoblast of 30 days. The patterns of trophoblast invasion in caviomorphs are analogous to the situation in humans, suggesting that these rodents are appropriate animal models for the study of the dynamics of trophoblast invasion.