Long-term follow-up, quality of life, and survival of patients with Lambert-Eaton myasthenic syndrome

Objective

To study survival and to characterize long-term functional impairments and health-related quality of life (HRQOL) of patients with Lambert-Eaton myasthenic syndrome (LEMS).

Methods

In this observational study, survival of patients with LEMS, separately for nontumor (NT) and small cell lung cancer (SCLC), was compared to that of the Dutch general population and patients with SCLC. Disease course in patients with LEMS was recorded retrospectively. Several scales for functional impairments and health-related quality of life were assessed.

Results

We included 150 patients with LEMS. Survival was similar to that of the general population in 65 patients with NT-LEMS. Tumor survival was significantly longer in 81 patients with SCLC-LEMS compared to patients with non-LEMS SCLC (overall median survival 17 vs 7.0 months, p < 0.0001). At diagnosis, 39 (62%) of 63 patients with complete follow-up data were independent for activities of daily living, improving to 85% at the 1-year follow-up. The physical HRQOL composite score (55.9) was significantly lower than in the general population (76.3, p < 0.0001) and comparable to that of patients with myasthenia gravis (60.5). The mental HRQOL composite score was 71.8 in patients with LEMS, comparable to that of the general population (77.9, p = 0.19) and patients with myasthenia gravis (70.3).

Conclusions

This study shows that patients with NT-LEMS have normal survival. Patients with SCLC-LEMS have an improved tumor survival, even after correction for tumor stage. A majority of patients with LEMS report a stable disease course and remain or become independent for self-care after treatment.

Novel UCHL1 mutations reveal new insights into ubiquitin processing

Recessive loss of function of the neuronal ubiquitin hydrolase UCHL1 has been implicated in early-onset progressive neurodegeneration (MIM no. 615491), so far only in one family. In this study a second family is characterized, and the functional consequences of the identified mutations in UCHL1 are explored. Three siblings developed childhood-onset optic atrophy, followed by spasticity and ataxia. Whole exome sequencing identified compound heterozygous variants in UCHL1, c.533G > A (p.Arg178Gln) and c.647C > A (p.Ala216Asp), cosegregating with the phenotype. Enzymatic activity of purified recombinant proteins analysed by ubiquitin hydrolase assays showed a 4-fold increased hydrolytic activity of the recombinant UCHL1 mutant Arg178Gln compared to wild type, whereas the Ala216Asp protein was insoluble. Structural 3D analysis of UCHL1 by computer modelling suggests that Arg178 is a rate-controlling residue in catalysis which is partly abolished in the Arg178Gln mutant and, consequently, the Arg178Gln mutant increases the enzymatic turnover. UCHL1 protein levels in fibroblasts measured by targeted mass spectrometry showed a total amount of UCHL1 in control fibroblasts about 4-fold higher than in the patients. Hence, studies of the identified missense variants reveal surprisingly different functional consequences as the insoluble Ala216Asp variant leads to loss of function, whereas the Arg178Gln leads to increased enzyme activity. The reported patients have remarkably preserved cognition, and we propose that the increased enzyme activity of the Arg178Gln variant offers a protective effect on cognitive function. This study establishes the importance of UCHL1 in neurodegeneration, provides new mechanistic insight about ubiquitin processing, and underlines the complexity of the different roles of UCHL1.

A polymorphic Alu insertion that mediates distinct disease-associated deletions

Large deletions that are associated with insertions of Alu-derived sequence represent a rare, but potentially unique class of alterations. Whether they form by a one-step mechanism or by a primary insertion step followed by an independent secondary deletion step is not clear. We resolved two disease-associated SPAST deletions, which involve distinct exons by long range PCR. Alu-derived sequence was observed between the breakpoints in both cases. The intronic regions that represent the targets of potentially involved Alu retrotransposition events overlapped. Microsatellite- and SNP-based haplotyping indicated that both deletions originated on one and the same founder allele. Our data suggest that the deletions are best explained by two-step insertion-deletion scenarios for which a single Alu retrotransposition event represents the shared primary step. This Alu then mediated one of the deletions by non-homologous end joining and the other by non-allelic homologous recombination. Our findings thus strongly argue for temporal separation of insertion and deletion in Alu insertion-associated deletions. They also suggest that certain Alu integrations confer a general increase in local genomic instability, and that this explains why they are usually not detected during the probably short time that precedes the rearrangements they mediate.

Multi-system neurological disease is common in patients with OPA1 mutations

Additional neurological features have recently been described in seven families transmitting pathogenic mutations in OPA1, the most common cause of autosomal dominant optic atrophy. However, the frequency of these syndromal 'dominant optic atrophy plus' variants and the extent of neurological involvement have not been established. In this large multi-centre study of 104 patients from 45 independent families, including 60 new cases, we show that extra-ocular neurological complications are common in OPA1 disease, and affect up to 20% of all mutational carriers. Bilateral sensorineural deafness beginning in late childhood and early adulthood was a prominent manifestation, followed by a combination of ataxia, myopathy, peripheral neuropathy and progressive external ophthalmoplegia from the third decade of life onwards. We also identified novel clinical presentations with spastic paraparesis mimicking hereditary spastic paraplegia, and a multiple sclerosis-like illness. In contrast to initial reports, multi-system neurological disease was associated with all mutational subtypes, although there was an increased risk with missense mutations [odds ratio = 3.06, 95% confidence interval = 1.44-6.49; P = 0.0027], and mutations located within the guanosine triphosphate-ase region (odds ratio = 2.29, 95% confidence interval = 1.08-4.82; P = 0.0271). Histochemical and molecular characterization of skeletal muscle biopsies revealed the presence of cytochrome c oxidase-deficient fibres and multiple mitochondrial DNA deletions in the majority of patients harbouring OPA1 mutations, even in those with isolated optic nerve involvement. However, the cytochrome c oxidase-deficient load was over four times higher in the dominant optic atrophy + group compared to the pure optic neuropathy group, implicating a causal role for these secondary mitochondrial DNA defects in disease pathophysiology. Individuals with dominant optic atrophy plus phenotypes also had significantly worse visual outcomes, and careful surveillance is therefore mandatory to optimize the detection and management of neurological disability in a group of patients who already have significant visual impairment.

Recent advances in hereditary spastic paraplegia

The hereditary spastic paraplegias are a group of rare disorders that are characterized by great clinical and genetic heterogeneity. There has been an exponential increase in the number of HSP loci mapped in recent years, with nine out of the 17 loci reported during the past 2 years. Eight loci have now been identified for the autosomal-dominant form, and seven of these are associated with pure HSP. Spastic paraplegia-4 remains the most frequent locus, and is usually associated with a pure phenotype. Although the corresponding spastin gene was only recently identified, over 50 mutations have been described to date, which renders molecular diagnosis difficult. Five loci are known for autosomal-recessive HSP, and four of these are associated with complex forms, all with different phenotypes. Two genes have been identified: paraplegin and sacsin. Finally, three loci have been identified in X-linked HSP, two of which are complex forms. The genes that encode L1 and PLP were the first to be identified in HSP disorders. Surprisingly, the five genes encode proteins of different families, making understanding and diagnosis of HSP even more difficult. The discovery of new genes should hopefully help to clarify the pathophysiology of these disorders.

Excitatory effect of thiamin on CA1 pyramidal neurones in rat hippocampal slices in vitro

Clinically, acute thiamin deficiency may lead to Wernicke encephalopathy and fulminant cardial beriberi. Both diseases respond to high parenteral doses of thiamin. The cofactor role of intracellular thiamin diphosphate has been thoroughly investigated, but an additional acute effect of unphosphorylated extracellular thiamin has been postulated but not elucidated. In order to investigate the role of thiamin at the membrane level in the central nervous system, a study using a well-established in vitro rat hippocampal slice model was designed. Hippocampal slices were perfused with 0.5, 0.75 and 1 mM thiamin solutions for 30 min and the pre-synaptic volley, field excitatory post-synaptic potential and population spike amplitudes were recorded continuously. The results showed an acute, excitatory effect of high-dose thiamin on hippocampal neurones by significantly increasing the number of repetitive afterdischarges. Additional experiments with low concentrations of the potassium channel blocker 4-aminopyridine showed similar findings. The results support previous evidence of thiamin affecting membrane ion channel activity, probably involving potassium channels, although the precise mechanisms of action are still unclear.

[Normal pressure hydrocephalus--evaluation of investigation procedures]

58 patients were investigated with a lumbar infusion test for normal pressure hydrocephalus in the department of neurology of the National Hospital between January 1991 and December 1996. We present a retrospective evaluation of the investigation protocol for these patients with suspected normal pressure hydrocephalus. The aim of the study was to find out whether specific prognostic factors could be identified by routine investigations. 20 patients had been referred to the department of neurosurgery and were subsequently shunted. A critical review of the criteria leading to surgical treatment (clinical symptoms, cerebral CT scan, infusion test, cisternography) is presented. There was no single variable which alone could discriminate normal pressure hydrocephalus from other types of hydrocephalus, or predict the outcome of shunting. A more systematic referral and clinical assessment of the patients together with a more precise evaluation of the findings and improved follow-up procedures are necessary for optimal selection of patients for surgery. The study also shows the importance of diagnosing these patients early, as delay in treatment appeared to worsen prognosis after shunting.

Visual hallucinations in a case of reversible hypertension-induced brain oedema

Visual hallucinations are commonly associated with seizures, drug effects, psychiatric disorders, or visual loss as 'release' phenomena. We report the case of a previously healthy 65-year-old woman, who was admitted to hospital with intermittent headache episodes accompanied by complex visual hallucinations. During these episodes the patient's blood pressure was 220/120 mmHg. In between symptomatic episodes she had no complaints and felt healthy. The neurological and ophthalmological examinations were normal but cerebral magnetic resonance imaging (MRI) showed multiple white matter abnormalities in the parieto-occipital regions. Rapid reversal of the symptoms and imaging abnormalities occurred concurrently with lowering of blood pressure. The history and the findings were similar to those recently described in the clinicoradiological 'posterior leukoencephalopathy' syndrome. Different pathogenic mechanisms are discussed. Copyright 1998 Lippincott Williams & Wilkins

[Thiamine treatment today]

This article reviews some of the established data on thiamin and the most common symptoms of deficiency. Guidelines for appropriate therapy are offered. Thiamin or vitamin B1 was among the first vitamins to be discovered. Beriberi was the first disease to be associated with thiamin deficiency, and Wernicke's encephalopathy was shown to respond to thiamin treatment a few years later. However, thiamin treatment remains inadequate or delayed. Treatment is efficient in the early stages, but delays often causes permanent damage. It is important that all physicians are aware of what patients are susceptible to develop thiamin deficiency and that they recognize the symptoms as early as possible.

Carbohydrate-deficient transferrin and other markers of high alcohol consumption: a study of 502 patients admitted consecutively to a medical department

An isoform of transferrin, carbohydrate-deficient transferrin (CDT) is increased in a high percentage of abusing alcoholics and has been found superior in its specificity compared with other biological markers. We used serum CDT as a screening parameter in 502 patients consecutively admitted to our medical department during a 4-week period. The intake of ethanol during the last 4 weeks was registrated by personal interviews and the mean daily consumption calculated. Serum CDT was measured at admission (CDTect) and compared with gamma-glutamyltranspeptidase (GGT), AST, ALT, and mean corpuscular volume (MCV). Serum CDT detected 18 of 26 (69%) patients who consumed > 50 g ethanol daily. The clinical sensitivity of CDT of detection ethanol consumption > 50 g daily was 69%, compared with 73%, 50%, 35%, and 52% for increased values of GGT, AST, ALT, and MCV, respectively. Altogether, 38 of 476 patients (8%) with a daily ethanol consumption < 50 g also had increased serum CDT levels. The specificity of CDT was 92%, compared with 75%, 82%, 86%, and 85% for GGT, AST, ALT, and MCV, respectively. In the 60 patients who consumed > 10 g ethanol daily, we found a significantly positive correlation between CDT and ethanol consumption (r = 0.52, p < 0.001). A positive correlation was also found between serum transferrin and CDT (r = 0.51, p < 0.001). In conclusion, the specificity of CDT is much higher compared with GGT in detecting alcohol abuse. Some acute and chronic illnesses may increase the serum level of CDT. False-positive CDT levels may be caused by changes in serum transferrin concentration.

Thiamin and thiamin phosphate ester deficiency assessed by high performance liquid chromatography in four clinical cases of Wernicke encephalopathy

The concentrations of thiamin and thiamin phosphate esters were determined by high performance liquid chromatography in four patients with clinical Wernicke encephalopathy. Three were alcohol abusers, and one had prolonged vomiting and anorexia. Thiamin and thiamin monophosphate were assessed in plasma and whole blood (four patients) and in cerebrospinal fluid (two patients) before and during thiamin treatment. Thiamin diphosphate was also assessed in whole blood in the four patients. Before treatment, thiamin monophosphate was significantly decreased in all patients, and thiamin diphosphate in three. A poor increase in thiamin mono- and diphosphate was paralleled by a slow clinical improvement in one patient, while an increase in all thiamin compounds was observed in two patients with a rapid recovery. Thiamin monophosphate was a more sensitive marker of deficiency than thiamin diphosphate and unphosphorylated thiamin.

Kinetics of thiamin and thiamin phosphate esters in human blood, plasma and urine after 50 mg intravenously or orally

The concentrations of thiamin and thiamin monophosphate and diphosphate in plasma and whole blood samples were assessed in six healthy subjects for 12 h and in urine for 24 h following an IV and PO bolus dose of 50 mg thiamin HCl. Unphosphorylated thiamin increased rapidly in plasma after IV administration and then decreased to its initial value within 12 h in all but one subject; the half-life was 96 min. Thiamin mono and -diphosphate increased moderately (56%), and decreased slowly; the half-life of diphosphate was 664 min. Within 24 h, 53% of the administered dose was recovered in the urine, indicating a restricted distribution. After oral administration, the peak thiamin concentration in plasma was reached after 53 min and the concentration then had increased to 179% of its initial value. The elimination half-life was 154 min, and only 2.5% of the given dose was recovered in the urine. The relative bioavailability of thiamin was 5.3%. A moderate amount of the administered thiamin was stored in blood. Other body tissues must play an important part, therefore, in the distribution of thiamin.

Concentrations of the water-soluble vitamins thiamin, ascorbic acid, and folic acid in serum and cerebrospinal fluid of healthy individuals

Thiamin, thiamin monophosphate, ascorbic acid, and folic acid were determined in serum and cerebrospinal fluid (CSF) in 31 outpatients who underwent a myelography because of back-pain. All subjects were otherwise healthy. The CSF concentration (mean +/- SD) was 8.6 +/- 3.9 nmol thiamin/L, 16.9 +/- 8.3 nmol thiamin monophosphate/L, 133 +/- 58.8 mumol ascorbic acid/L, and 44.9 +/- 13.2 nmol folic acid/L. The CSF-serum ratio was 2.1 +/- 0.8 for thiamin, 8.3 +/- 4.3 for thiamin monophosphate, 3.0 +/- 1.4 for ascorbic acid, and 3.3 +/- 0.8 for folic acid; the amount in CSF was significantly higher than in serum for each compound. These results support the existence of a saturated transport mechanism of water-soluble vitamins from serum into CSF for thiamin monophosphate, ascorbic acid, and folic acid. However, low CSF concentrations are correlated with low serum concentrations for the three vitamins. High serum concentrations should therefore be advocated to ensure high CSF concentrations.

The concentration of thiamin and thiamin phosphate esters in patients with alcoholic liver cirrhosis

The blood and plasma concentrations of thiamin and thiamin phosphate esters were determined concomitantly by high-performance liquid chromatography (HPLC) in 22 patients with alcoholic liver cirrhosis, and also in 10 of them 24 hr after a 100 mg thiamin i.m. injection. Sixteen patients were abstaining from alcohol at the time of the study, 6 were currently misusing alcohol. The control group included 30 healthy volunteers, of whom 10 were given the same thiamin injection as the patients. Blood thiamin diphosphate was the only compound decreased in the abstaining patients compared to controls (70.9 +/- 21.9 nmol/l vs. 84.4 +/- 19.0 nmol/l), but all thiamin compounds in blood and plasma were decreased in the misusing patients. All thiamin compounds (except blood monophosphate) were also significantly lower in the misusing than in the abstaining patients (plasma thiamin: 5.3 +/- 1.3 vs. 11.7 +/- 8.3 nmol/l; plasma monophosphate: 1.0 +/- 1.1 vs. 4.1 +/- 2.9 nmol/l; blood diphosphate: 45.7 +/- 18.3 vs. 70.9 +/- 21.9 nmol/l). Thiamin phosphorylation ratio was decreased in the patients after thiamin administration compared to controls (2.83 +/- 0.74 vs. 3.68 +/- 0.58). Plasma thiamin was higher in the abstaining patients than in the controls (11.7 +/- 8.4 nmol/l vs. 7.3 +/- 2.5 nmol/l), and above the mean + 2 SD of the controls in 31% of the abstaining patients. In conclusion, current ethanol misuse is associated with low thiamin concentrations, and liver cirrhosis is associated with a decreased thiamin diphosphate concentration and thiamin phosphorylation.

Blood and serum thiamin and thiamin phosphate esters concentrations in patients with alcohol dependence syndrome before and after thiamin treatment

The blood and serum concentrations of free thiamin and its three phosphate esters were determined concomitantly by a new high-performance liquid chromatography (HPLC) method in 30 patients with alcohol dependence syndrome on admission to hospital and 24 hr after thiamin injection. We studied 24 men and 6 women; mean age, 50 years (range 21 to 69); mean ethanol consumption during the last 30 days, 164 +/- 119 g/day. A control group included 40 healthy volunteers (25 men, 15 women), of whom 10 were given the same thiamin injection as were the patients. Thiamin monophosphate was significantly reduced in the patients compared with controls before treatment (men 2.9 +/- 2.3 and 5.9 +/- 3.1 nmol/liter) and after (8.1 +/- 5.1 and 19.5 +/- 8.1 nmol/liter). On admission, free thiamin and thiamin diphosphate were similar in controls and in patients in whole blood (B) and serum (S) and increased similarly after treatment (mean B-thiamin diphosphate in male patients: 149 +/- 64 to 238 +/- 88 nmol/liter, in controls: 179 +/- 40 to 289 +/- 18 nmol/liter). However, seven patients had extremely high free thiamin values. The phosphorylation ratio was lower in patients than in controls (p less than 0.05), before and after treatment. Finally, the mean B-diphosphate was lower in patients not taking vitamins (116 +/- 48 nmol/liter and 172 +/- 57 nmol/liter) and in patients with polyneuropathy (118 +/- 54 nmol/liter and 173 +/- 52 nmol/liter), compared with the other patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Concomitant determination of thiamin and its phosphate esters in human blood and serum by high-performance liquid chromatography

A high-performance liquid chromatographic method for the simultaneous determination of thiamin and thiamin phosphate esters in human blood or serum has been developed. The eluent consists of acetonitrile and phosphate buffer, in the ratios 90:10 (v/v) for the elution of thiamine and 60:40 (v/v) for the phosphate esters. The four compounds are eluted within 15 min. The detection limit is 13-16 fmol. Between-assay variation is 5-11%. Samples of whole blood and serum from 30 healthy adults were analysed. The following reference values were obtained for 15 females 15 males (nM, mean +/- S.D.). In serum: thiamin, 10.9 +/- 2.9/16.9 +/- 3.3; thiamin monophosphate, 8.3 +/- 1.5/3.7 +/- 1.5. In whole blood: thiamin, 29.6 +/- 10.0/33.4 +/- 10.4; thiamin monophosphate, 9.7 +/- 2.3/10.9 +/- 5.1; thiamin diphosphate, 121 +/- 29.6/165 +/- 40.4.