A novel phenotype of AChR-deficiency syndrome with predominant facial and distal weakness resulting from the inclusion of an evolutionary alternatively-spliced exon in CHRNA1

Primary acetylcholine receptor deficiency is the most common subtype of congenital myasthenic syndrome, resulting in reduced amount of acetylcholine receptors expressed at the muscle endplate and impaired neuromuscular transmission. AChR deficiency is caused mainly by pathogenic variants in the ε-subunit of the acetylcholine receptor encoded by CHRNE, although pathogenic variants in other subunits are also seen. We report the clinical and molecular features of 13 patients from nine unrelated kinships with acetylcholine receptor deficiency harbouring the CHRNA1 variant NM_001039523.3:c.257G>A (p.Arg86His) in homozygosity or compound heterozygosity. This variant results in the inclusion of an alternatively-spliced evolutionary exon (P3A) that causes expression of a non-functional acetylcholine receptor α-subunit. We compare the clinical findings of this group to the other cases of acetylcholine receptor deficiency within our cohort. We report differences in phenotype, highlighting a predominant pattern of facial and distal weakness in adulthood, predominantly in the upper limbs, which is unusual for acetylcholine receptor deficiency syndromes, and more in keeping with slow-channel syndrome or distal myopathy. Finally, we stress the importance of including alternative exons in variant analysis to increase the probability of achieving a molecular diagnosis.

MuSK not MNGIE: Atypical MuSK-antibody myasthenia presenting as a genetic disorder

Myasthenia gravis is a treatable autoimmune disease caused by autoantibodies directed against membrane proteins at the neuromuscular junction. While acetylcholine receptor antibodies are most common, a minority of patients have antibodies directed against muscle-specific kinase (MuSK-antibody). Differentiating features often include subacute onset and rapid progression of bulbar, respiratory and neck extensor muscles, with sparing of distal appendicular muscles, most commonly in middle-aged females. Here we present an atypical presentation of MuSK-antibody myasthenic syndrome in a young male consisting of a gradual-onset, insidiously-progressive, non-fatigable and non-fluctuating ocular, bulbar and oesophageal weakness, with a normal frontalis single fibre EMG. This case clinically resembled a mitochondrial myopathy (Mitochondrial Neurogastrointestinal Encephalopathy-MNGIE) with a poor prognosis. Because of the atypical presentation, MuSK antibodies were identified very late in the disease course, at which point the patient responded very well to immunotherapy. We report an unusual presentation of an uncommon but treatable condition, illustrating significant phenotypic heterogeneity possible in MuSK-antibody myasthenic syndrome.

Prediction of Cognitive Status and 5-Year Survival Rate for Elderly with Cardiovascular Diseases: A Canadian Study of Health and Aging Secondary Data Analysis

BACKGROUND

Given the important association between cardiovascular disease and cognitive decline, and their significant implications on frailty status, the contribution of neurocognitive frailty measure helping with the assessment of patient outcomes is dearly needed.

OBJECTIVES

The present study examines the prognostic value of the Neurocognitive Frailty Index (NFI) in the elderly with cardiovascular disease.

DESIGN

Secondary analysis of the Canadian Study of Health and Aging (CSHA) dataset was used for prediction of 5-year cognitive changes.

SETTING

Community and institutional sample.

PARTICIPANTS

Canadians aged 65 and over [Mean age: 80.4 years (SD=6.9; Range of 66-100)].

MEASUREMENT

Neurocognitive Frailty Index (NFI) and Modified Mini-Mental State (3MS) scores for cognitive functioning of all subjects at follow-up and mortality rate were measured.

RESULTS

The NFI mean score was 9.63 (SD = 6.04) and ranged from 0 to 33. This study demonstrated that the NFI was significantly associated with cognitive changes for subjects with heart disease and this correlation was a stronger predictor than age.

CONCLUSION

The clinical relevance of this study is that our result supports the prognostic utility of the NFI tool in treatment planning for those with modifiable cardiovascular disease risk factors in the development of dementia.

Dying of amyotrophic lateral sclerosis

Objective

To describe health care service utilization and cost for decedents with and without amyotrophic lateral sclerosis (ALS) in the last year of life.

Methods

Using linked health administrative data, we conducted a retrospective, population-based cohort study of Ontario, Canada, decedents from 2013 to 2015. We examined demographic data, rate of utilization, and cost of health care services in the last year of life.

Results

We identified 283,096 decedents in Ontario, of whom 1,212 (0.42%) had ALS. Decedents with ALS spent 3 times as many days in an intensive care unit (ICU) (mean 6.3 vs 2.1, p < 0.001), and twice as many days using complex continuing care (mean 12.7 vs 6.0, p < 0.001) and home care (mean 99.1 vs 41.3, p < 0.001). A greater percentage of decedents with ALS received palliative home care (44% vs 20%, p < 0.001) and palliative physician home visits (40% vs 18%, p < 0.001) than decedents without ALS. Among decedents with ALS, a palliative physician home visit in the last year of life was associated with reduced adjusted odds of dying in hospital (odds ratio 0.65, 95% confidence interval 0.48–0.89) and fewer days spent in the ICU. Mean cost of care in the last year of life was greater for those with ALS ($68,311.98 vs $55,773.48, p < 0.001).

Conclusions

In this large population-based cohort of decedents, individuals with ALS spent more days in the ICU, received more community-based services, and incurred higher costs of care in the last year of life. A palliative care physician home visit was associated with improved end of life outcomes; however, the majority of patients with ALS did not access such services.

PDXK mutations cause polyneuropathy responsive to pyridoxal 5'-phosphate supplementation

OBJECTIVE

To identify disease-causing variants in autosomal recessive axonal polyneuropathy with optic atrophy and provide targeted replacement therapy.

METHODS

We performed genome-wide sequencing, homozygosity mapping, and segregation analysis for novel disease-causing gene discovery. We used circular dichroism to show secondary structure changes and isothermal titration calorimetry to investigate the impact of variants on adenosine triphosphate (ATP) binding. Pathogenicity was further supported by enzymatic assays and mass spectroscopy on recombinant protein, patient-derived fibroblasts, plasma, and erythrocytes. Response to supplementation was measured with clinical validated rating scales, electrophysiology, and biochemical quantification.

RESULTS

We identified biallelic mutations in PDXK in 5 individuals from 2 unrelated families with primary axonal polyneuropathy and optic atrophy. The natural history of this disorder suggests that untreated, affected individuals become wheelchair-bound and blind. We identified conformational rearrangement in the mutant enzyme around the ATP-binding pocket. Low PDXK ATP binding resulted in decreased erythrocyte PDXK activity and low pyridoxal 5'-phosphate (PLP) concentrations. We rescued the clinical and biochemical profile with PLP supplementation in 1 family, improvement in power, pain, and fatigue contributing to patients regaining their ability to walk independently during the first year of PLP normalization.

INTERPRETATION

We show that mutations in PDXK cause autosomal recessive axonal peripheral polyneuropathy leading to disease via reduced PDXK enzymatic activity and low PLP. We show that the biochemical profile can be rescued with PLP supplementation associated with clinical improvement. As B6 is a cofactor in diverse essential biological pathways, our findings may have direct implications for neuropathies of unknown etiology characterized by reduced PLP levels. ANN NEUROL 2019;86:225-240.

Intraoperative flash VEPs are reproducible in the presence of low amplitude EEG

Flash visual evoked potentials (FVEPs) are often irreproducible during surgery. We assessed the relationship between intraoperative FVEP reproducibility and EEG amplitude. Left then right eyes were stimulated by goggle light emitting diodes, and FVEPs were recorded from Oz–Fz′ (International 10-20 system) in 12 patients. Low cut filters were ≤5 Hz in all patients; two patients also had recordings using 10 and 30 Hz. The reproducibility of FVEP and the amplitude of the concomitant EEG from C4′–Fz were measured. Nine patients had low amplitude EEG (<30 μV); reproducible FVEPs were obtained from all eyes with normal pre-operative vision. The other three patients had high amplitude EEG (>50 μV); FVEPs were absent from three of four eyes with normal pre-operative vision (the other normal eye had a present but irreproducible FVEP). Raising the low cut filter to 10 and 30 Hz (in two patients) progressively reduced EEG and FVEP amplitude, reduced amplifier blocking time and improved FVEP reproducibility. FVEPs were more reproducible in the presence of low amplitude EEG than high amplitude EEG. This is the first report describing the effect of EEG amplitude on FVEP reproducibility during surgery

Microvessel basement membrane reduplication is not associated with repeated nerve fiber degeneration and regeneration

To determine whether repeated nerve fiber degeneration and regeneration can induce reduplication of endoneurial microvessel basement membranes (BMs), typical of such conditions as diabetic polyneuropathy, electronmicrographs of endoneurial microvessels of rat peroneal and tibial nerves were studied in repeatedly crushed (10 x) sciatic nerves and compared to microvessels of sham-operated uncrushed nerves. On average, crushed nerves had 2.6, SE +/- 0.1 BMs, whereas control nerves had 2.7, SE +/- 0.1 (P > 0.05). Microvessel cellular components were significantly increased in both number and size in the crushed nerves. These nerves also demonstrated a trend to increased vessel numbers and density. These results are not in keeping with the hypothesis that BM reduplication of endoneurial microvessels is simply due to repeated fiber degeneration and regeneration.

{The perception of mental health professionals of barriers to the delivery of mental health services for the aged in New Brunswick}

The present survey examines the barriers associated with the delivery of mental health services to the elderly as perceived by mental health professionals. The sample consisted of 139 professionals of the New Brunswick Mental Health Commission. The results reveal that the mean percentage of elderly clients in the practice of mental health professionals is low. The percentage of elderly clients in the practice of mental health professionals was positively correlated with training in gerontology. The attitudes of the respondents toward the elderly were either positive or neutral rather than negative. In addition, the results show that the barriers perceived by the professionals to explain the low utilization rates differ in order of importance from those acknowledged by the elderly. The lack of human resources was identified as the major barrier to the development of specific consultation services to the elderly. Finally, the implications of these results for the development of mental health consultation services for the elderly are examined.

Time estimation and concurrent nontemporal processing: specific interference from short-term-memory demands

Previous studies have shown that the effect of concurrent nontemporal processing on time estimation may vary depending on the level of difficulty of the nontemporal task. This is commonly interpreted within the context of so-called distraction/interruption models of temporal processing, which propose that as concurrent task difficulty or complexity is increased, temporal processing receives less attention. We hypothesize that the effect of nontemporal processing does not depend on the level of difficulty as such, but rather on the extent to which the concurrent nontemporal task specifically involves processing in short-term memory. Four experiments were run in which the short-term memory requirements of concurrent tasks were systematically varied, although all of the tasks were of comparable levels of difficulty. In the first experiment, the effect of memory search on simultaneous temporal productions was proportional to the number of items to search. As with reaction time, produced intervals were shown to increase linearly with the number of items in the memorized set. In Experiment 2, a visual search involving some load on short-term memory interfered in the same way with time production, although to a lesser extent. The last two experiments showed that performing attention-demanding visual search tasks that did not involve short-term memory did not lengthen simultaneously produced time intervals. This suggests that interference of nontemporal processing on time processing may not be a matter of nonspecific general purpose attentional resources, but rather of concurrent short-term-memory processing demands.

Plasma exchange in polyneuropathy associated with monoclonal gammopathy of undetermined significance

BACKGROUND

Polyneuropathy associated with monoclonal gammopathy of undetermined significance (MGUS) has been treated with plasma exchange, intravenous immune globulin, and chemotherapy, but the effectiveness of these treatments remains uncertain.

METHODS

We randomly assigned 39 patients with stable or worsening neuropathy and MGUS of the IgG, IgA, or IgM type to receive either plasma exchange twice weekly for three weeks or sham plasma exchange, in a double-blind trial. The patients who initially underwent sham plasma exchange subsequently underwent plasma exchange in an open trial.

RESULTS

In the double-blind trial, the average neuropathy disability score improved by 2 points from base line (from 62.5 to 60.5) in the sham-exchange group and by 12 points (from 58.3 to 46.3) in the plasma-exchange group (P = 0.06). A similar difference was observed in the weakness score, a component of the neuropathy disability score (improvement, 1 and 10 points, respectively; P = 0.07). After treatment the summed compound muscle action potentials of motor nerves were 1.2 mV lower (worse) than at base line in the sham-exchange group and 0.4 mV higher (better) in the plasma-exchange group (P = 0.07). The greater degree of improvement with plasma exchange was equal in magnitude to or greater than the difference between not being able to walk on the heels or toes and being able to perform these activities. Changes in the vibratory detection threshold, summed motor-nerve conduction velocity, and sensory-nerve action potentials did not differ significantly between the treatment groups. In the open trial, in which patients who initially underwent sham exchange were treated with plasma exchange, the neuropathy disability score (P = 0.04), weakness score (P = 0.07), and summed compound muscle action potentials (P = 0.07) improved more with plasma exchange than they had with sham exchange. In both the double-blind and the open trial, those with IgG or IgA gammopathy had a better response to plasma exchange than those with IgM gammopathy.

CONCLUSIONS

Plasma exchange appears to be efficacious in neuropathy associated with MGUS, especially of the IgG or IgA type.

Effect of functional appliances on jaw muscle activity

The electromyographic (EMG) activity of masticatory muscles was monitored longitudinally with chronically implanted EMG electrodes to determine whether functional appliances produce a change in postural EMG activity of the muscles. Preappliance and postappliance EMG levels in four experimentals that had been fitted with functional appliances were compared against the background of EMG levels in controls without appliances. The insertion of two types of functional appliance to induce mandibular protrusion was associated with a decrease in postural EMG activity of the superior and inferior heads of the lateral pterygoid, superficial masseter, and anterior digastric muscles; the decrease in the first three muscles was statistically significant. This decreased postural EMG activity persisted for approximately 6 weeks, with a gradual return toward preappliance levels during a subsequent 6-week period of observation. Progressive mandibular advancement of 1.5 to 2 mm every 10 to 15 days did not prevent the decrease in postural EMG activity.