Pharmacosafety of fluoroquinolone and macrolide antibiotics in the clinical care of patients with myasthenia gravis

INTRODUCTION/AIMS

Anecdotal case reports have suggested a potential association of fluoroquinolones and macrolides with myasthenia gravis (MG) exacerbation, prompting warnings against the use of these drugs in this population. However, large-scale and reliable population-based data that demonstrate this association are lacking. This study aims to examine the association between outpatient treatment with fluoroquinolones or macrolides and MG-related hospitalization.

METHODS

A retrospective cohort study consisting of adult MG patients was conducted using a large de-identified healthcare claims database. Antibiotic prescription claims were identified, and MG-related hospitalizations were assessed at 15, 30, and 90 days after the date of prescription. We used mixed effects survival regression with log-logistic distribution and independent covariance matrix to estimate odds ratios (ORs) of hospitalization for each potentially exacerbating antibiotic using beta-lactam as the reference and adjusting for covariates.

RESULTS

Among 1556 MG patients receiving 894 fluoroquinolone prescriptions, 729 macrolide prescriptions, and 1608 beta-lactam prescriptions during the study period, there was no difference in 15, 30, or 90-day odds of MG-related hospitalization between fluoroquinolone or macrolide users compared to prescribed beta-lactams. However, estimates were higher for fluoroquinolones than macrolides, even after covariate adjustment (adjusted OR [aOR] 4.60, 95% confidence interval [CI] 0.55-38.57 for fluoroquinolones and OR 0.56, 95% CI 0.32-0.97 for macrolides, respectively, at 15 days).

DISCUSSION

Fluoroquinolone and macrolide antibiotics are prescribed frequently to patients with MG. While statistical imprecision precludes a definitive conclusion, elevated ORs for fluoroquinolones raise the possibility of an underpowered association that merits further investigation.

Diagnosis and management of critical illness polyneuropathy and critical illness myopathy

Newly acquired neuromuscular weakness commonly develops in the setting of critical illness. This weakness delays recovery and often causes prolonged ventilator dependence. An axonal sensory-motor polyneuropathy, critical illness polyneuropathy (CIP), is seen in up to a third of critically ill patients with the systemic inflammatory response syndrome (usually due to sepsis). As frequently, or more so, an acute myopathy, critical illness myopathy (CIM), develops in a similar setting, often in association with the use of corticosteroids and/or nondepolarizing neuromuscular-blocking agents. This paper reviews the clinical features, diagnostic approach, and treatment of CIP and CIM. There are no specific pharmacologic treatments for CIP or CIM, but recognizing the presence of one of these disorders often improves management. Prevention of CIP and CIM is feasible in part by avoiding risk factors and by aggressive medical management of critically ill patients. Intensive insulin therapy in intensive care unit patients appears to reduce the likelihood of developing CIP and/or CIM. Future treatments of sepsis may further reduce the incidence of these neuromuscular consequences of critical illness.

Myasthenia gravis with presynaptic electrophysiologic abnormalities

OBJECTIVES

To describe the clinical, serologic, and electrophysiologic features of 2 patients with myasthenia gravis (MG), who also had presynaptic electrophysiologic abnormalities.

METHODS

Case reports.

RESULTS

Two patients developed clinical symptoms consistent with MG. They lacked autonomic symptoms or signs, and their reflexes were not absent. Acetylcholine receptor antibody studies were positive, but assays for voltage-gated calcium channel antibodies were negative. Low-amplitude baseline compound muscle action potentials combined with large incremental responses immediately after exercise were consistent with a presynaptic disorder. Thymic pathology in 1 patient was characteristic of autoimmune MG showing lymphoid follicular hyperplasia. No underlying malignancy was found in either patient.

CONCLUSIONS

Patients with MG may rarely have presynaptic electrophysiologic abnormalities. This may occur even in the absence of the typical clinical and serologic features of the Lambert-Eaton syndrome. It is possible that there is another antibody present that is modulating presynaptic acetylcholine release.

Value of repeated measures of nerve conduction and quantitative sensory testing in a diabetic neuropathy trial

Conduct of a large, multicenter trial of the aldose reductase inhibitor zenarestat provided data on the reproducibility of multiple electrophysiologic (nerve conduction studies, NCS) and quantitative sensory (QST) tests. Baseline and 12-month electrophysiologic data from approximately 1100 patients at multiple centers were available for analysis. Intersite variability contributed minimally to overall test variance. All NCS tests were highly reproducible. Cool thermal and vibration QST thresholds, as measured by CASE IV instrumentation, were also highly reproducible. Intersubject variance accounted for the majority of variance for all parameters measured. Repeating NCS and QST measures decreased sample sizes needed to show statistical significance. Consideration of these observations, particularly with regard to QST, should aid in the design of future clinical trials investigating neuropathy.

Encephalopathy and peripheral neuropathy following diethylene glycol ingestion

The authors report a 24-year-old man who developed encephalopathy and rapid quadriplegia following ingestion of a solution containing diethylene glycol (DEG). As quadriparesis evolved, motor response amplitudes were markedly reduced with preserved conduction velocities. Studies during clinical recovery revealed marked motor conduction velocity slowing and prolonged distal latencies. These data indicate that DEG intoxication may cause a primary acute axonal sensorimotor polyneuropathy with demyelinating physiology during recovery.

Involvement of skeletal muscle in dialysis-associated systemic fibrosis (nephrogenic fibrosing dermopathy)

Nephrogenic fibrosing dermopathy (NFD), a newly recognized scleroderma-like disease, was originally described as a purely cutaneous disorder. More widespread involvement, including fibrosis of pulmonary and cardiac tissues, has been documented only recently, and it has been suggested that a more appropriate designation is dialysis-associated systemic fibrosis. We report five cases of this novel disorder, spanning a spectrum of primarily skin to primarily muscle involvement. Clinical, radiological, electrophysiological, and pathological studies revealed moderate to severe fibrosis of striated muscles. All patients had end-stage renal failure on chronic dialysis, subacute to chronic hardening of the skin and muscles, restriction of limb movements with joint contractures, but normal to only mildly weak muscle strength. Limitation of movements was caused predominantly by skin tightness and induration, and by joint contractures rather than muscle weakness. Computerized tomography showed fibrosis of the fascia and muscles in the most severely affected patients, and electromyography showed mild to severe myopathic changes. Histopathology of affected muscles revealed a spectrum of mild to severe fibrosis, degenerating fibers, and chronic inflammatory cells. These results further support the contention that NFD is not a purely cutaneous disease, but is part of a larger systemic fibrotic process that may involve muscles.

Natural progression of diabetic peripheral neuropathy in the Zenarestat study population

OBJECTIVE

The aim of this study was to report the baseline and natural progression of diabetic peripheral neuropathy over 12 months in a large mild-to-moderate neuropathy population.

RESEARCH DESIGN AND METHODS

Patients from a multicentered trial of zenarestat, an aldose reductase inhibitor, had serial measures of neurologic function, including nerve conduction studies (NCSs), quantitative sensory testing (QST), and clinical neuropathy rating scores at baseline and at 12 months. Baseline population descriptors and changes in neurologic function in placebo-treated patients were analyzed.

RESULTS

Sural sensory velocity (P = 0.0008 [95% CI -1.04 to -0.27]), median sensory amplitude (P = 0.0021 [-1.3 to -0.29]), median distal motor latency (P = 0.002 [0.09-0.28]), cool thermal QST (P = 0.0005 [0.27-0.94]), and Michigan Neuropathy Screening Instrument results (P = 0.0087 [0.04-0.30]) declined significantly from baseline in the placebo population. NCS changes from baseline were independent of baseline HbA1c stratification.

CONCLUSIONS

The neurologic decline over 12 months is evident when measured by NCS and cool thermal QST. Other measures (vibration QST, neuropathy rating scores, monofilament examination) are insensitive to changes over 12 months in a mild-to-moderate affected population of this size.

Critical illness myopathy and polyneuropathy

Neuromuscular weakness commonly develops in the setting of critical illness. This weakness delays recovery and often causes prolonged ventilator dependence. An axonal sensory-motor polyneuropathy, critical illness polyneuropathy (CIP), is seen in up to one third of critically ill patients with the systemic inflammatory response syndrome (usually due to sepsis). An acute myopathy, critical illness myopathy (CIM), frequently develops in a similar setting, often in association with the use of corticosteroids and/or nondepolarizing neuromuscular blocking agents. These patients are often difficult to evaluate due to the limitations imposed by the critical care setting and may be further complicated by the presence of both CIP and CIM in varying degrees. This paper reviews the clinical and electrophysiologic features of these disorders, as well as the putative pathophysiology. In the case of CIM, an animal model has provided evidence that weakness in this disorder is caused by muscle membrane inexcitability due to altered membrane sodium currents and loss of myosin thick filaments.

Transcervical thymectomy for myasthenia gravis achieves results comparable to thymectomy by sternotomy

BACKGROUND

It remains controversial whether transcervical thymectomy offers results equivalent to thymectomy by way of a median sternotomy in the treatment of myasthenia gravis. Furthermore, preoperative prognostic factors have not been clearly defined.

METHODS

This study is a retrospective chart review and interview of 78 patients completing transcervical thymectomy for myasthenia gravis between 1992 and 1999.

RESULTS

There were 24 men and 54 women. Mean age was 40 years (range, 13 to 78 years). Twelve patients were in Osserman class 1, 25 in class 2, 30 in class 3, and 11 in class 4 (mean, 2.5). There was no perioperative mortality and 6 (7.7%) morbidities. Mean length of stay was 1.5 days and mean follow-up, 54.6 months. The crude cumulative complete remission (asymptomatic off medications for 6 months) rate was 39.7% (n = 31). Only 8 patients (10.3%) failed to improve after transcervical thymectomy. Kaplan-Meier estimates of complete remission were 31% and 43% at 2 and 5 years, respectively. Eight patients with thymoma had a 5-year estimated complete remission rate of 75% in contrast to 43% in 38 patients with thymic hyperplasia and 36% in 32 patients with neither thymoma nor hyperplasia (p = 0.01). Twelve patients with ocular myasthenia had a 5-year estimated complete remission rate of 57%, whereas patients with mild-to-moderate (n = 55) or severe (n = 11) generalized symptoms had 5-year complete remission rates of 43% and 30%, respectively (p = 0.21).

CONCLUSIONS

Overall, extended transcervical thymectomy offers results that are comparable to those published for the transsternal procedure. Patients with milder disease (including isolated ocular disease) and taking no preoperative immunosuppressive agents appear to experience higher remission rates. In contrast to previous studies, we also find that small thymomas predict better responses to thymectomy.

Mentors, advisors and supervisors: their role in teaching responsible research conduct

Although the terms mentor and thesis advisor (or research supervisor) are often used interchangeably, the responsibilities associated with these roles are distinct, even when they overlap. Neither are role models necessarily mentors, though mentors are role models: good examples are necessary but not sufficient. Mentorship is both a personal and a professional relationship. It has the potential for raising a number of ethical concerns, including issues of accuracy and reliability of the information conveyed, access, stereotyping and tracking of advises, and the abuse of power. Nevertheless, mentors can be critically important for professional success and are one of a number of elements that affect the responsible conduct of research. In addition, the community as a whole has a responsibility to mentor junior members.

Scientific certainty: research versus forensic perspectives

The scientific community and the judicial system are different components of society with different structures and functions. Nevertheless, science can contribute relevant and useful information to judicial deliberations if the inherent limitations of that information are understood. These limitations stem from the way the information is presented and perceived both by those who are providing it and those who are providing the context in which it is presented.

Acute axonal neuropathy in maple syrup urine disease

A 25-year-old woman with maple syrup urine disease (MSUD) developed generalized weakness over 1 week. She had severe leg and moderate arm weakness, areflexia, and distal sensory loss. Plasma branched-chain amino acid concentrations were elevated, reflecting an acute exacerbation of the disease. Electrodiagnostic studies indicated an acute axonal polyneuropathy and sural nerve biopsy revealed acute wallerian degeneration without inflammation. Peripheral neuropathy, although not identified previously as a clinical feature of MSUD, may become more common as chronic dietary restrictions and improved management of the disease allow survival into adulthood.

Ross syndrome plus: beyond horner, Holmes-Adie, and harlequin

BACKGROUND

Ross syndrome is an uncommon disorder characterized by the triad of segmental anhidrosis, hyporeflexia, and tonic pupils.

METHODS

The authors describe the clinical findings of five patients with Ross syndrome and detail the results of their pharmacologic and autonomic testing.

RESULTS

In four patients, the classic findings of Ross syndrome were accompanied by Horner's syndrome. Other symptoms of dysautonomia were also common.

CONCLUSIONS

These findings suggest that Ross syndrome is a dysautonomic condition of varying expression resulting from a generalized injury to ganglion cells or their projections.

Chronic multiple paraneoplastic syndromes

A patient presented with symptoms of limbic and brainstem encephalitis, motor and sensory neuronopathy, cerebellar dysfunction, and highly positive anti-Hu antibodies. He also harbored P/Q-type calcium channel antibodies and manifested the Lambert-Eaton myasthenic syndrome (LEMS). Small-cell lung cancer was found, and he received both antineoplastic therapy and intravenous immunoglobulin (IVIg). Remission of the malignancy was achieved. Although the anti-Hu-related manifestations improved after therapy, LEMS has persisted, leading to IVIg dependency.

Of mice and men (and women and children): scientific and ethical implications of animal models

1. Animal models of human behavior and disease are commonly used and have contributed significantly to progress in understanding the physiological mechanisms of both normal function and disease, and in the development of effective therapies. 2. Little attention has been given, however, to the scientific and ethical implications of choosing a particular animal model. 3. This paper discusses the rationale for the selection of particular animal models that have been chosen to study certain human diseases or behaviors, and provides examples to illustrate how underlying assumptions about methods and about physiological mechanisms and other relevant features of the disease or behavior of interest are embedded in the choice of an animal model. 4. Although these assumptions influence the direction of research, they are rarely analyzed explicitly, or evaluated empirically. The authors recommend that assumptions should be clearly stated and that, whenever possible, they be specifically and thoroughly evaluated empirically.

Ethical issues in communicating science

Most of the publicized work on scientific ethics concentrates on establishing professional norms and avoiding misconduct. The successful communication of science is the responsibility of all involved in the process. In one study, the increased incidence of autism and other social developmental disorders in males was investigated by examining individuals with Turner's syndrome (XO females). In the national newspaper this became "Genetic X-factor explains why boys will always be boys". The steps by which a study on developmental disorders, published in a highly prestigious journal, was transformed into an article in the science section which 'explained' the socially expected gender-based behavior of genetically normal children are fascinating and, unfortunately far too typical. The scientists wrote an excellent article that has just one sentence at the end that hesitantly suggests that the findings might, with further study, have some relevance to understanding normal behavior. The general interest article in the front of the journal gave a good account of the research, but suggested more strongly that there could be an in-built biological dimorphism in social cognition. This was misrepresented in the press as proof of gender differences that "undermines the trend towards sexual equality", and both illustrates cultural bias and provides fodder for feminist critiques of science. The study has been made to appear to be biased in favor of justifying the social structure of society, and yet it was the translation from the scientific study to national news that produced this transformation to biased genetic determinism. It is poor communication of the actual science, coupled with a lack of skepticism on the part of the public, that contributes to such a misapplication of science. Scientists should resist the urge to generalize their results to make them more compelling. The science community should not allow misconstructions of scientific facts to go unchallenged. Journalists, for both the scientific publication and the newspaper, should resist the inclination to embellish the finding with social significance that is not present. For their part, readers must be doubly skeptical of any finding that appears to underwrite any current social hierarchy. We are all responsible for a communication and interpretation of science that is as accurate and socially responsible as possible.

Serial evoked potential studies and MRI imaging in chronic progressive multiple sclerosis

Measurements of serial evoked potential latencies and plaque burden on MRI scans are often obtained during clinical studies of multiple sclerosis patients to provide additional information to the disability-based primary endpoints. The ideal laboratory-based marker of progression would be expected to significantly change over the time period of study. Serial visual (VEP) and brainstem auditory evoked potentials (BAEP) and MRI scans of 11 chronic progressive MS patients were obtained over a 1.5 year period in a clinical study. Over this period, there was no significant change in disability as measured by the Kurtzke EDSS, Ambulation Index or Neurological Rating Score. The VEP P100 significantly progressed over the period of study. However, the MRI T(2) plaque burden and BAEP I-V intrapeak latency did not significantly progress over the 1.5 years. We conclude that, in chronic progressive MS, serial visual evoked potential tests may complement standard disability-based endpoints to assess disease progression.

A double-blind, placebo-controlled trial of extracorporeal photopheresis in chronic progressive multiple sclerosis

Extracorporeal photopheresis is a safe therapy for cutaneous T-cell lymphoma and may have efficacy in certain autoimmune disorders. We performed a randomized, double-blinded, placebo-controlled trial of monthly photopheresis therapy in 16 patients with clinically definite multiple sclerosis (MS). All patients had progressed during the preceding year with entry Expanded Disability Status Scale (EDSS) scores between 3.0 and 7.0. Patients received photopheresis or sham therapy for 1 year and were followed for an additional 6 to 12 months. Patients were clinically evaluated by three disability scales: (1) EDSS; (2) Ambulation index and (3) Scripp's quantitative neurologic assessment. No serious side effects occurred in either group. There were no differences between the photopheresis and sham therapy groups by the disability measures. Additionally, there were no differences in progression of MRI plaque burden or evoked potential latencies. In this limited study, photopheresis was found to be safe but did not significantly alter the course of chronic progressive MS.

Iatrogenic superior gluteal mononeuropathy

Injuries to the superior gluteal nerve (SGN) have been reported as a result of trauma, pyriformis muscle entrapment, injections, and lumbar lordosis and inadequate back stabilization. We report 3 patients who developed isolated SGN injuries, 1 after a partial nephrectomy and 2 following revision of a total hip arthroplasty. SGN should be suspected in anyone developing an abnormal gait after hip or pelvic surgery or after prolonged lateral decubitus positioning.

Bulbocavernosus reflex studies and autonomic testing in the diagnosis of erectile dysfunction

The electrophysiologic evaluation of patients with erectile dysfunction presents an important diagnostic challenge. The bulbocavernosus reflex (BCR) latency has been commonly used to evaluate these disorders. However, it is a measure of somatic penile innervation, whereas erection is primarily dependent on autonomic function. We evaluated 195 men with erectile dysfunction over a 3 year period. Each had electrophysiologic studies, nerve conduction studies and a BCR. BCR studies were abnormal in only 7%, of which most had diabetes or pelvic trauma. The BCR was the sole electrophysiologic abnormality in only 2%. Autonomic testing (AT) was additionally performed in 19 diabetic and 23 non-diabetic patients. This included sympathetic skin responses and measurement of the Valsalva ratio and heart rate variability with 6/min breathing. In the diabetic group, AT was positive in 63%, and most often was the sole abnormality. The bulbocavernosus reflex is relatively insensitive in the diagnosis of erectile dysfunction. Brief autonomic testing may provide valuable additional data, particularly in diabetics.

Autosomal dominant transmission of Dejerine-Sottas disease (HMSN III)

Hereditary motor-sensory neuropathy type III (HMSN III) (Dejerine-Sottas disease) is a severe demyelinating neuropathy that is traditionally considered autosomal recessive. We report a father and daughter diagnosed with HMSN III by clinical, electrophysiologic, and pathologic criteria, thus showing that it may be transmitted in an autosomal dominant fashion in selected families.

Direct muscle stimulation in acute quadriplegic myopathy

We have previously found that muscle is electrically inexcitable in severe acute quadriplegic myopathy (AQM). In contrast, muscle retains normal electrical excitability in peripheral neuropathy. To study the relationship between muscle electrical excitability and all types of flaccid weakness occurring in the intensive care unit, we identified 14 critically ill, weak patients and measured the amplitude of compound muscle action potentials (CMAPs) obtained with direct muscle stimulation (dmCMAP) and with nerve stimulation (neCMAP). In 11 of 14 patients dmCMAP amplitudes were reduced and the ratio of the neCMAP amplitude to the dmCMAP amplitude (nerve/muscle ratio) was indicative of loss of muscle electrical excitability. In 2 other patients, the nerve/muscle ratio indicated neuropathy. Direct muscle stimulation may allow differentiation of AQM from neuropathy even in comatose or encephalopathic critically ill patients. AQM may be more common than has previously been appreciated.

Posterior cervical spinal cord infarction following vertebral artery dissection

There are only two reported cases of unilateral posterior cervical spinal cord infarction as a result of vertebral artery dissection. We describe the first reported case of bilateral posterior spinal cord infarction caused by vertebral artery dissection.

Chronic inflammatory demyelinating polyneuropathy associated with malignant melanoma

We report three patients who developed chronic inflammatory demyelinating polyneuropathy (CIDP) in association with malignant melanoma. In two cases, melanoma was discovered during the initial evaluation for neuropathy. Two patients also had vitiligo, an antibody-mediated disorder that may complicate melanoma. Melanoma cells and Schwann cells are both of neuroectodermal cell origin, with shared surface antigens. Shared immunoreactivity may account for the association between melanoma and CIDP, as with vitiligo.

Muscle is electrically inexcitable in acute quadriplegic myopathy

We directly stimulated muscle in three patients with acute quadriplegic myopathy to determine whether paralyzed muscle in this syndrome is electrically excitable. Two of the patients had been treated with neuromuscular blocking agents and corticosteroids, and one patient had been treated with corticosteroids alone. We found that paralyzed muscle is electrically inexcitable in affected patients. Muscle regained electrical excitability over weeks to months. The recovery of muscle excitability paralleled the clinical recovery of patients, suggesting that paralysis in this syndrome is secondary to electrical inexcitability of muscle membrane.

Site of autonomic dysfunction in a patient with Ross' syndrome and postganglionic Horner's syndrome

Ross' syndrome is a rare peripheral nervous system disorder defined by Adie's tonic pupil, hyporeflexia, and segmental anhidrosis. Injury to postganglionic cholinergic fibers is believed to account for the tonic pupil and sweating disturbance. We report a 47-year-old man found to have Ross' syndrome in combination with a complete postganglionic Horner's syndrome. Pharmacologic and sudomotor tests in this unique patient provide further evidence that Ross' syndrome results from injury to sympathetic and parasympathetic ganglion cells or to their postganglionic projections.

Mechanism of lysosome rupture by dipeptides

Low concentrations of some neutral dipeptides, such as L-Ala-L-Ala, rapidly disrupt rat liver lysosomes. The phenomenon has been attributed to an osmotic imbalance generated by the production of amino acids in the lysosome by lysosomal dipeptidase activity. This hypothesis is challenged by testing several pairs of dipeptides available in both D- and L-forms and a range of dipeptides whose susceptibility to lysosomal dipeptidase activity is known. A good correlation was found between the lytic ability of dipeptides and their capacity to cross the lysosome membrane and be hydrolysed by lysosomal dipeptidase. The osmotic-imbalance hypothesis is critically evaluated in the light of the results and of recent information concerning the carrier-mediated transport of amino acids and dipeptides across the lysosome membrane. It is concluded that intralysosomal generation of amino acids remains the most plausible explanation of the lytic activity of dipeptides, and that the dipeptide porter(s) in the lysosome membrane must have higher Km than the amino acid porters.

Prolonged muscle weakness after neuromuscular blockade in the intensive care unit

As noted, quadriparesis with reduced reflexes and difficulty with ventilator weaning may be seen as a result of a number of neuromuscular disorders. The clinical approach relies on exclusion of a central cause first, followed by careful examination of peripheral nerve and muscle function. Persistent neuromuscular blockade should be excluded initially because it is a readily reversible condition. Use of a train of four stimulation with a peripheral twitch monitor can quickly establish integrity of conduction across the neuromuscular junction. If necessary, further electrophysiologic studies allow differentiation among the relevant diagnostic possibilities. CIP is characterized by nerve conduction and EMG findings consistent with axonal degeneration of sensory and motor fibers. GBS is distinguished by evidence of demyelination on nerve conduction studies, in addition to elevated spinal fluid protein. Persistent neuromuscular blockade is identified by a decremental response on repetitive stimulation studies of neuromuscular transmission. The acute myopathy following neuromuscular blockage does not involve sensory responses. Needle EMG examination reflects a myopathic pattern, rather than a neurogenic one as seen in CIP or GBS. In myopathic patients who are unable to move their limbs at all (precluding a full EMG examination), a muscle biopsy identifies muscle as the site of involvement.

Spontaneous remission of a third-nerve palsy in meningeal lymphoma

We report on a patient with spontaneous remission of a third-nerve palsy who was subsequently found to have meningeal lymphoma. Initial magnetic resonance images (MRI) showed bilateral enhancement of the third nerves. Follow-up MRI 7 months later, without treatment, showed complete resolution. One year after initial presentation, the patient developed multiple lumbosacral radiculopathies and examination of a nerve root biopsy specimen disclosed a B-cell lymphoma. Serial cerebrospinal fluid analyses over the previous year showed occasional atypical cells, later found to resemble closely the biopsy cell type. We conclude that meningeal lymphoma may have a protracted course, with spontaneous remission of both clinical and neuroimaging findings.

Stimulated single-fiber electromyography in Lambert-Eaton myasthenic syndrome

The Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of neuromuscular transmission. Electrodiagnosis is confirmed by an increase in compound muscle action potential amplitude during high-frequency repetitive nerve stimulation or following brief exercise. We describe the results of stimulated single-fiber electromyography in 4 patients with disorders of neuromuscular transmission: LEMS (2), LEMS/myasthenia gravis (MG) overlap (1), and MG (1). Stimulated SFEMG was performed in the extensor digitorum communis muscle with axonal intramuscular suprathreshold stimulation at low and high rates. In all 4 patients, a rate dependence of jitter was found. In LEMS and LEMS/MG, jitter and blocking improved with high stimulation rates, as compared with the opposite effect in MG. We conclude that stimulated SFEMG is a valuable technique in the diagnosis of LEMS.