Autonomic dysfunction in the Lambert-Eaton myasthenic syndrome: serologic and clinical correlates

Autonomic nervous system involvement in autoimmune encephalitis and paraneoplastic neurological syndromes

In autoimmune neurological diseases, the autonomic nervous system can be the primary target of autoimmunity (e.g. autoimmune autonomic ganglionopathy), or, more frequently, be damaged together with other areas of the nervous system (e.g. Guillain-Barré syndrome). Patients with autoimmune encephalitis and paraneoplastic neurological syndromes (PNS) often develop dysautonomia; however, the frequency and spectrum of autonomic signs and symptoms remain ill defined except for those scenarios in which dysautonomia is a core feature of the disease. Such is the case of Lambert-Eaton myasthenic syndrome, Morvan syndrome or anti-NMDAR encephalitis; in the latter, patients with dysautonomia have been reported to carry a more severe disease and to retain higher disability than those without autonomic dysfunction. Likewise, the presence of autonomic involvement indicates a higher risk of death due to neurological cause in patients with anti-Hu PNS. However, in anti-Hu and other PNS, as well as in the context of immune checkpoint inhibitors' toxicities, the characterization of autonomic involvement is frequently overshadowed by the severity of other neurological symptoms and signs. When evaluated with tests specific for autonomic function, patients with autoimmune encephalitis or PNS usually show a more widespread autonomic involvement than clinically suggested, which may reflect a potential gap of care when it comes to diagnosing dysautonomia. This review aims to revise the autonomic involvement in patients with autoimmune encephalitis and PNS, using for that purpose an antibody-based approach. We also discuss and provide general recommendations for the evaluation and management of dysautonomia in these patients.

Paraneoplastic neuropathies and peripheral nerve hyperexcitability disorders

Peripheral neuropathy is a common referral for patients to the neurologic clinics. Paraneoplastic neuropathies account for a small but high morbidity and mortality subgroup. Symptoms include weakness, sensory loss, sweating irregularity, blood pressure instability, severe constipation, and neuropathic pain. Neuropathy is the first presenting symptom of malignancy among many patients. The molecular and cellular oncogenic immune targets reside within cell bodies, axons, cytoplasms, or surface membranes of neural tissues. A more favorable immune treatment outcome occurs in those where the targets reside on the cell surface. Patients with antibodies binding cell surface antigens commonly have neural hyperexcitability with pain, cramps, fasciculations, and hyperhidrotic attacks (CASPR2, LGI1, and others). The antigenic targets are also commonly expressed in the central nervous system, with presenting symptoms being myelopathy, encephalopathy, and seizures with neuropathy, often masked. Pain and autonomic components typically relate to small nerve fiber involvement (nociceptive, adrenergic, enteric, and sudomotor), sometimes without nerve fiber loss but rather hyperexcitability. The specific antibodies discovered help direct cancer investigations. Among the primary axonal paraneoplastic neuropathies, pathognomonic clinical features do not exist, and testing for multiple antibodies simultaneously provides the best sensitivity in testing (AGNA1-SOX1; amphiphysin; ANNA-1-HU; ANNA-3-DACH1; CASPR2; CRMP5; LGI1; PCA2-MAP1B, and others). Performing confirmatory antibody testing using adjunct methods improves specificity. Antibody-mediated demyelinating paraneoplastic neuropathies are limited to MAG-IgM (IgM-MGUS, Waldenström's, and myeloma), with the others associated with cytokine elevations (VEGF, IL6) caused by osteosclerotic myeloma, plasmacytoma (POEMS), and rarely angiofollicular lymphoma (Castleman's). Paraneoplastic disorders have clinical overlap with other idiopathic antibody disorders, including IgG4 demyelinating nodopathies (NF155 and Contactin-1). This review summarizes the paraneoplastic neuropathies, including those with peripheral nerve hyperexcitability.

Paraneoplastic autonomic neuropathies and GI dysmotility

A number of the well-recognized autoimmune and paraneoplastic neurologic syndromes commonly involve the autonomic nervous system. In some cases, the autonomic nerves or ganglia are primary targets of neurologic autoimmunity, as in immune-mediated autonomic ganglionopathies. In other disorders such as encephalitis, autonomic centers in the brain may be affected. The presence of autonomic dysfunction (especially gastrointestinal dysmotility) is sometimes overlooked even though this may contribute significantly to the symptom burden in these paraneoplastic disorders. Additionally, recognition of autonomic features as part of the clinical syndrome can help point the diagnostic evaluation toward autoimmune and paraneoplastic etiologies. As with other paraneoplastic disorders, the clinical syndrome and the presence and type of neurologic autoantibodies help to secure the diagnosis and direct the most appropriate investigation for malignancy. Optimal management for these conditions typically includes aggressive treatment of the neoplasm, immunomodulatory therapy, and symptomatic treatments for orthostatic hypotension and gastrointestinal dysmotility.

Lambert-Eaton myasthenic syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disease characterized by proximal muscle weakness, loss of tendon reflexes, and autonomic dysfunction. Muscle weakness usually starts in the upper legs and can progress to oculobulbar and in severe cases respiratory muscles. P/Q-type voltage-gated calcium channels (VGCCs) localized in the presynaptic motor nerve terminal and in the autonomic nervous system are targeted by antibodies in LEMS patients. These antibodies can be detected in about 90% of patients, and the presence of decrement and increment upon repetitive nerve stimulation is also a highly sensitive diagnostic test. Rapid diagnosis is important because of the association with SCLC in 50%-60% of patients, which stresses the need for vigorous tumor screening after diagnosis. Clinical parameters can predict tumor probability and guide frequency of tumor screening. Treatment of the tumor as well as symptomatic treatment and immunosuppression can effectively control symptoms in the majority of patients.

Lambert-Eaton Myasthenic Syndrome in Lung Cancer

The aim is to study lung cancer with Lambert-Eaton myasthenic syndrome (LEMS) with clinical and electrical characteristics of physiology and prognosis. Fourteen LEMS patients with lung cancer were studied retrospectively. The data including demographics, clinical presentation, treatments, and prognosis from the medical records were analyzed. Lung cancer coexisting with LEMS is more common in men (10/14). The median age was 67.1 years. Eleven (78.6%) patients experienced gradual onset of disease. Most patients presented nervous system lesions prior to occult tumors. The most common symptoms reported were proximal muscle weakness (92.9%), decreased or absent tendon reflexes (50%), and autonomic dysfunction (71.4%). All the patients showed reduction in action potential amplitude after repetitive peripheral never stimulation at low frequency and increased amplitude at high frequency. LEMS usually occurs prior to lung cancer with complicated and various clinical manifestations in our centers. We should improve awareness and knowledge of such disease to shorten the diagnostic delay and lead to few misdiagnoses.

Autonomic dysfunction detected by skin sympathetic response in Lambert-Eaton myasthenic syndrome: a case report

Background

Lambert-Eaton myasthenic syndrome (LEMS) is a type of paraneoplastic syndrome that may initially manifest itself with proximal weakness and gait abnormalities. Approximately up to 50% of LEMS patients have a primary autonomic dysfunction.

Case presentation

We present here a case of a 75-year-old male with symmetric proximal muscle weakness, dry mouth and constipation. The cutaneous response to scratch and upright tilt-table testing were positive. A repetitive nerve stimulation test showed that there was a decremental response of compound muscle action potential (CMAP) amplitude at 3 Hz while an incremental response at 20 Hz. The presence of antibodies against voltage-gated calcium channels (VGCC) confirmed the diagnosis. Because of the prominent symptom of autonomic disorder, the patient further underwent the test of skin sympathetic response (SSR). Lower amplitude and longer response duration were found in palms, while it evoked no response in soles.

Conclusions

In this case, we present the detailed results of SSR test on a patient suffering LEMS with autonomic disorder. Since autonomic dysfunction has a significant impact on clinical management and SSR test is an effective detection method, we recommend that SSR test be performed on patients with LEMS regularly.

Presynaptic Paraneoplastic Disorders of the Neuromuscular Junction: An Update

The neuromuscular junction (NMJ) is the target of a variety of immune-mediated disorders, usually classified as presynaptic and postsynaptic, according to the site of the antigenic target and consequently of the neuromuscular transmission alteration. Although less common than the classical autoimmune postsynaptic myasthenia gravis, presynaptic disorders are important to recognize due to the frequent association with cancer. Lambert Eaton myasthenic syndrome is due to a presynaptic failure to release acetylcholine, caused by antibodies to the presynaptic voltage-gated calcium channels. Acquired neuromyotonia is a condition characterized by nerve hyperexcitability often due to the presence of antibodies against proteins associated with voltage-gated potassium channels. This review will focus on the recent developments in the autoimmune presynaptic disorders of the NMJ.

The emerging role of the sympathetic nervous system in skeletal muscle motor innervation and sarcopenia

Examining neural etiologic factors'role in the decline of neuromuscular function with aging is essential to our understanding of the mechanisms underlying sarcopenia, the age-dependent decline in muscle mass, force and power. Innervation of the skeletal muscle by both motor and sympathetic axons has been established, igniting interest in determining how the sympathetic nervous system (SNS) affect skeletal muscle composition and function throughout the lifetime. Selective expression of the heart and neural crest derivative 2 gene in peripheral SNs increases muscle mass and force regulating skeletal muscle sympathetic and motor innervation; improving acetylcholine receptor stability and NMJ transmission; preventing inflammation and myofibrillar protein degradation; increasing autophagy; and probably enhancing protein synthesis. Elucidating the role of central SNs will help to define the coordinated response of the visceral and neuromuscular system to physiological and pathological challenges across ages. This review discusses the following questions: (1) Does the SNS regulate skeletal muscle motor innervation? (2) Does the SNS regulate presynaptic and postsynaptic neuromuscular junction (NMJ) structure and function? (3) Does sympathetic neuron (SN) regulation of NMJ transmission decline with aging? (4) Does maintenance of SNs attenuate aging sarcopenia? and (5) Do central SN group relays influence sympathetic and motor muscle innervation?

Sudomotor Dysfunction

Disorders of sudomotor function are common and diverse in their presentations. Hyperhidrosis or hypohidrosis in generalized or regional neuroanatomical patterns can provide clues to neurologic localization and inform neurologic diagnosis. Conditions that impair sudomotor function include small fiber peripheral neuropathy, sudomotor neuropathy, myelopathy, α-synucleinopathies, autoimmune autonomic ganglionopathy, antibody-mediated hyperexcitability syndromes, and a host of medications. Particularly relevant to neurologic practice is the detection of postganglionic sudomotor deficits as a diagnostic marker of small fiber neuropathies. Extensive anhidrosis is important to recognize, as it not only correlates with symptoms of heat intolerance but may also place the patient at risk for heat stroke when under conditions of heat stress. Methods for assessing sudomotor dysfunction include the thermoregulatory sweat test, the quantitative sudomotor axon reflex test, silicone impressions, and the sympathetic skin response.

Autoimmune Autonomic Disorders

PURPOSE OF REVIEW

Autonomic disorders sometimes occur in the context of systemic autoimmune disease or as a direct consequence of autoimmunity against the nervous system. This article provides an overview of autonomic disorders with potential autoimmune etiology.

RECENT FINDINGS

Recent evidence highlights a close association between the autonomic nervous system and inflammation. The autonomic nervous system regulates immune function, and autonomic manifestations may occur in a number of systemic autoimmune diseases. In a few instances, autoimmunity directly influences autonomic function. Autoimmune autonomic ganglionopathy is the prototypic antibody-mediated autonomic disorder. Over time, a better understanding of the clinical spectrum of autoimmune autonomic ganglionopathy, the significance of ganglionic nicotinic acetylcholine receptor antibodies, other immune-mediated autonomic neuropathies, and autonomic manifestations of other systemic or neurologic autoimmune disorders has emerged.

SUMMARY

Autoimmune autonomic disorders may be challenging, but correct identification of these conditions is important. In some cases, potential exists for effective immunomodulatory treatment.

The sympathetic nervous system regulates skeletal muscle motor innervation and acetylcholine receptor stability

AIM

Symptoms of autonomic failure are frequently the presentation of advanced age and neurodegenerative diseases that impair adaptation to common physiologic stressors. The aim of this work was to examine the interaction between the sympathetic and motor nervous system, the involvement of the sympathetic nervous system (SNS) in neuromuscular junction (NMJ) presynaptic motor function, the stability of postsynaptic molecular organization, and the skeletal muscle composition and function.

METHODS

Since muscle weakness is a symptom of diseases characterized by autonomic dysfunction, we studied the impact of regional sympathetic ablation on muscle motor innervation by using transcriptome analysis, retrograde tracing of the sympathetic outflow to the skeletal muscle, confocal and electron microscopy, NMJ transmission by electrophysiological methods, protein analysis, and state of the art microsurgical techniques, in C57BL6, MuRF1KO and Thy-1 mice.

RESULTS

We found that the SNS regulates motor nerve synaptic vesicle release, skeletal muscle transcriptome, muscle force generated by motor nerve activity, axonal neurofilament phosphorylation, myelin thickness, and myofibre subtype composition and CSA. The SNS also modulates the levels of postsynaptic membrane acetylcholine receptor by regulating the Gαi2 -Hdac4-Myogenin-MuRF1pathway, which is prevented by the overexpression of the guanine nucleotide-binding protein Gαi2 (Q205L), a constitutively active mutant G protein subunit.

CONCLUSION

The SNS regulates NMJ transmission, maintains optimal Gαi2 expression, and prevents any increase in Hdac4, myogenin, MuRF1, and miR-206. SNS ablation leads to upregulation of MuRF1, muscle atrophy, and downregulation of postsynaptic AChR. Our findings are relevant to clinical conditions characterized by progressive decline of sympathetic innervation, such as neurodegenerative diseases and aging.

Differential diagnosis of idiopathic inflammatory myopathies in adults - the first step when approaching a patient with muscle weakness

Despite its misleading adjective, the most commonly used diagnostic criteria of idiopathic inflammatory myopathies (IIM) are applicable only after all other non-autoimmune muscle diseases have been excluded. It makes differential diagnosis the first step when approaching a patient with muscle weakness. This article is designed to list the most common conditions from which to differentiate in rheumatological care. In fact, many patients with the diseases described here have been initially misdiagnosed with IIM. For the purpose of this article, only the most commonly found and important conditions according to the authors are listed with the essence of information; other autoimmune muscle diseases, such as sarcoidosis and eosinophilic myositis, are not portrayed. The attached bibliography may serve as a source, when further exploration of a specific subject is needed.

Autoimmune paraneoplastic syndromes associated to lung cancer: A systematic review of the literature Part 4: Neurological paraneoplastic syndromes, involving the peripheral nervous system and the neuromuscular junction and muscles

The development of new immune treatment in oncology and particularly for lung cancer may induce new complications, particularly activation or reactivation of auto-immune diseases. In this context, a systematic review on the auto-immune paraneoplastic syndromes that can complicate lung cancer appears useful. This article is the fourth of a series of five and deals mainly with neurological paraneoplastic syndromes involving the peripheral nervous system and the neuromuscular junction and muscles.

Neuromuscular junction disorders

Diseases of the neuromuscular junction comprise a wide range of disorders. Antibodies, genetic mutations, specific drugs or toxins interfere with the number or function of one of the essential proteins that control signaling between the presynaptic nerve ending and the postsynaptic muscle membrane. Acquired autoimmune disorders of the neuromuscular junction are the most common and are described here. In myasthenia gravis, antibodies to acetylcholine receptors or to proteins involved in receptor clustering, particularly muscle-specific kinase, cause direct loss of acetylcholine receptors or interfere with the agrin-induced acetylcholine receptor clustering necessary for efficient neurotransmission. In the Lambert-Eaton myasthenic syndrome (LEMS), loss of the presynaptic voltage-gated calcium channels results in reduced release of the acetylcholine transmitter. The conditions are generally recognizable clinically and the diagnosis confirmed by serologic testing and electromyography. Screening for thymomas in myasthenia or small cell cancer in LEMS is important. Fortunately, a wide range of symptomatic treatments, immunosuppressive drugs, or other immunomodulating therapies is available. Future research is directed to understanding the pathogenesis, discovering new antigens, and trying to develop disease-specific treatments.

Review of the Diagnostic Challenges of Lambert–Eaton Syndrome Revealed Through Three Case Reports

Lambert–Eaton syndrome (LES) is a rare immune-mediated disorder characterized by proximal leg weakness, autonomic symptoms and hypoactive tendon reflexes. The paraneoplastic form is associated with small-cell lung cancer in 50-60% of cases, whereas the remaining cases are found in younger adults with a higher likelihood of coexisting autoimmune disease. The early recognition of LES is crucial for improving clinical outcomes but remains a major challenge. In this review, we analyze the clinical characteristics and diagnostic considerations in treating LES through a series of three case studies, one of which showed definitive response to pyridostigmine and corticosteroid combination therapy, followed by spontaneous remission. Patients were assessed by image-based screening, serological testing and electrophysiological evaluations, which included respiratory and autonomic testing. A better understanding of the common pitfalls in the clinical, serological and neurophysiologic diagnosis of LES through assessment of typical LES dysfunction throughout the nervous system should enable improved recognition and treatment of this syndrome.

Autoimmune-mediated peripheral neuropathies and autoimmune pain

Peripheral neuropathies have diverse acquired and inherited causes. The autoimmune neuropathies represent an important category where treatment is often available. There are overlapping signs and symptoms between autoimmune neuropathies and other forms. Making a diagnosis can be challenging and first assisted by electrophysiologic and sometimes pathologic sampling, with autoimmune biomarkers providing increased assistance. Here we provide a review of the autoimmune and inflammatory neuropathies, their available biomarkers, and approaches to treatment. Also discussed is new evidence to support a mechanism of autoimmune pain.

Synaptic Pathophysiology and Treatment of Lambert-Eaton Myasthenic Syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease that disrupts the normally reliable neurotransmission at the neuromuscular junction (NMJ). This disruption is thought to result from an autoantibody-mediated removal of a subset of the P/Q-type Ca(2+) channels involved with neurotransmitter release. With less neurotransmitter release at the NMJ, LEMS patients experience debilitating muscle weakness. The underlying cause of LEMS in slightly more than half of all patients is small cell lung cancer, and cancer therapy is the priority for these patients. In the remaining cases, the cause of LEMS is unknown, and these patients often rely on symptomatic treatment options, as there is no cure. However, current symptomatic treatment options, such as 3,4-diaminopyridine (3,4-DAP), can have significant dose-limiting side effects; thus, additional treatment approaches would benefit LEMS patients. Recent studies introduced a novel Ca(2+) channel agonist (GV-58) as a potential therapeutic alternative for LEMS. Additionally, this work has shown that GV-58 and 3,4-DAP interact in a supra-additive manner to completely restore the magnitude of neurotransmitter release at the NMJs of a LEMS mouse model. In this review, we discuss synaptic mechanisms for reliability at the NMJ and how these mechanisms are disrupted in LEMS. We then discuss the current treatment options for LEMS patients, while also considering recent work demonstrating the therapeutic potential of GV-58 alone and in combination with 3,4-DAP.

Pathogenic immune mechanisms at the neuromuscular synapse: the role of specific antibody-binding epitopes in myasthenia gravis

Autoantibodies against three different postsynaptic antigens and one presynaptic antigen at the neuromuscular junction are known to cause myasthenic syndromes. The mechanisms by which these antibodies cause muscle weakness vary from antigenic modulation and complement-mediated membrane damage to inhibition of endogenous ligand binding and blocking of essential protein-protein interactions. These mechanisms are related to the autoantibody titre, specific epitopes on the target proteins and IgG autoantibody subclass. We here review the role of specific autoantibody-binding epitopes in myasthenia gravis, their possible relevance to the pathophysiology of the disease and potential implications of epitope mapping knowledge for new therapeutic strategies.

Cardiovascular manifestations of neurologic disease

Cardiac manifestations of neurologic diseases are common in clinical practice. There are numerous anatomic and pathophysiologic links between the normal and abnormal function of both systems. There are a number of brain-heart interactions which affect the care of patients as well as help guide therapeutic development. This is exemplified in the area of vascular neurology where knowledge of the brain-heart connection is essential not only for bedside management but where collaborative efforts between neurology and cardiology are key in developing new strategies for ischemic stroke prevention and treatment, atrial fibrillation, and interventional techniques. This chapter will focus on cardiac manifestations of neurologic disease, with special emphasis on vascular and intensive care neurology, epilepsy, and neurodegenerative and peripheral nervous system diseases.

A pediatric case of severe pandysautonomia responsive to plasmapheresis

We describe a 13-year-old female with abrupt onset urinary retention progressing rapidly to pandysautonomia with symptoms of postural orthostatic tachycardia syndrome, gastroparesis, anhidrosis, pupillary dysfunction, and abdominal pain. Pandysautonomia has been reported frequently in adults, but is less commonly described in children. Autonomic nervous system dysfunction usually has a self-limiting course with gradual near-complete or complete recovery. Most patients with pure pandysautonomia produce an antibody targeted against the ganglionic nicotinic acetylcholine receptor and titers have been shown to correlate with symptom severity. The clinical presentation described in this report is consistent with a progressive form of acute autoimmune autonomic neuropathy, but she was initially seronegative for known autoantibodies. She responded promptly to plasmapheresis. This case report emphasizes the importance of recognizing features of autonomic nervous system dysfunction and discusses the medical evaluation and treatment options for pediatric patients based on symptom severity.

Myasthenia gravis, thymoma, and intestinal pseudo-obstruction: a case report and review

We report a 28-year-old man who presented with intestinal pseudo-obstruction as the initial manifestation of thymoma, myasthenia gravis, and dysautonomia. The patient's autoantibody profile was characteristic of this constellation of disorders, being positive for both muscle and ganglionic nicotinic acetylcholine receptor antibodies and striational antibody. Inflammatory cell infiltrates were found in the myenteric plexus of the stomach and small intestine. Review of 12 previously reported cases suggests that patients with both myasthenia gravis and dysautonomia in the context of thymoma respond poorly to therapy.

Case report: a case review of Lambert-Eaton myasthenic syndrome and low back pain

The following is a case report which reviews the essential aspects of Lambert-Eaton myasthenic syndrome (LEMS) in a patient with long standing back pain and gait dysfunction. The patient was referred to our electrodiagnostics laboratory for a 9-month history of low back pain and difficulty walking following a charity breast cancer walk. A workup including magnetic resonance imaging of the brain, entire spine, and EMG/NCS at another institution were reportedly normal. A detailed history revealed symptoms of proximal weakness and autonomic dysfunction. Physical findings were consistent with proximal weakness, a bilateral gluteus medius gait, and diffusely absent reflexes obtainable in the biceps after 3 s of contraction. Electrical testing revealed an initial low compound muscle action potential amplitude in the deep peroneal nerve recording from the extensor digitorum brevis. Repetitive stimulation at 2 Hz revealed a decremental response of 42% from the 1st response to the 4th response. Following 3 s of exercise, the amplitude increased by 300%. After 30 s of exercise followed by 1 min of rest, there was a return of the decremental response. The history, physical examination, and electrical findings were illustrative of a presynaptic neuromuscular junction disorder, specifically LEMS.

Update on treatment options for Lambert-Eaton myasthenic syndrome: focus on use of amifampridine

In Lambert-Eaton myasthenic syndrome (LEMS), antibodies against presynaptic voltage-gated calcium channels reduce the quantal release of acetylcholine, causing muscle weakness and autonomic dysfunction. More than half of the affected patients have associated small cell lung cancer, and thorough screening for an underlying malignancy is crucial. The mainstay of treatment for LEMS is symptomatic but immunotherapy is needed in more severely affected patients. Symptomatic therapies aim at increasing the concentration of acetylcholine at the muscle endplate. While acetylcholinesterase inhibitors were the first drugs to be used for the amelioration of symptoms, 3,4-diaminopyridine (3,4-DAP, amifampridine) has been shown to be more effective. 3,4-DAP blocks presynaptic potassium channels, thereby prolonging the action potential and increasing presynaptic calcium concentrations. This then results in increased quantal release of acetylcholine. The efficacy of 3,4-DAP for increasing muscle strength and resting compound muscle action potentials has been demonstrated by four placebo-controlled trials. Side effects are usually mild, and the most frequently reported are paresthesias. The most common serious adverse events are epileptic seizures. 3,4-DAP is currently the treatment of choice in patients with Lambert-Eaton myasthenic syndrome.

Update on paraneoplastic neurologic disorders

When patients with cancer develop neurologic symptoms, common causes include metastasis, infections, coagulopathy, metabolic or nutritional disturbances, and neurotoxicity from treatments. A thorough clinical history, temporal association with cancer therapies, and results of ancillary tests usually reveal one of these mechanisms as the etiology. When no etiology is identified, the diagnosis considered is often that of a paraneoplastic neurologic disorder (PND). With the recognition that PNDs are more frequent than previously thought, the availability of diagnostic tests, and the fact that, for some PNDs, treatment helps, PNDs should no longer be considered diagnostic zebras, and when appropriate should be included in the differential diagnosis early in the evaluation.

Update on paraneoplastic neurologic disorders

Once considered rare, paraneoplastic neurologic disorders (PNDs) are an extensive group of neurologic disorders that occur either exclusively or at increased frequency in patients with cancer. PNDs have been increasingly recognized due in large part to the identification of antineuronal antibodies in the serum and cerebrospinal fluid of patients. Although almost any neoplasm can cause PND, the tumors most commonly involved are small-cell lung cancer, cancers of the breast and ovary, thymoma, neuroblastoma, plasma cell tumors, and ovarian teratoma. Establishing the diagnosis of PND is important because in more than two-thirds of patients the neurologic symptoms develop before the presence of the cancer is known. When PND is suspected and no tumor is found, it is recommended that cancer screening be repeated every 6 months. Early diagnosis and intervention offers the best chance of neurologic stabilization or improvement.

Neural autoantibody profile of primary achalasia

The etiology and pathogenesis of primary achalasia are both unknown. Postulated mechanisms include autoimmune, viral-immune, and central neurodegenerative. The aim of this study is to investigate the serum profile of neural autoantibodies in patients with primary achalasia. Coded sera from 70 patients with primary achalasia and 161 healthy control subjects, matched in sex, age, and smoking habits, were screened for antibodies targeting neuronal, glial, and muscle autoantigens. No specific myenteric neuronal antibody was identified. However, the overall prevalence of neural autoantibodies in patients with primary achalasia was significantly higher than in healthy control subjects (25.7 vs. 4.4%, P < 0.0001). Most noteworthy was the 21.4% frequency of glutamic acid decarboxylase-65 antibody in patients with achalasia (versus 2.5% in control subjects), in the absence of diabetes or companion antibodies predictive of type 1 diabetes. This profile of autoantibodies suggests an autoimmune basis for a subset of primary achalasia.

Association of N-type calcium channel autoimmunity in patients with autoimmune autonomic ganglionopathy

The nicotinic acetylcholine receptor (nAChR) antibody directly contributes to the autonomic dysfunction in Autoimmune Autonomic Ganglionopathy (AAG). The pathological mechanism leading to autonomic dysfunction in seronegative AAG is unclear. We evaluated patients with presumed antibody negative AAG (n=49) to determine whether there was an association with other autoantibodies. Three patients met the clinical criteria and were positive for N-type calcium channel antibodies. All patients had severe autonomic dysfunction characterized by orthostatic hypotension and gastrointestinal involvement. Autonomic testing revealed severe impairment of sudomotor, cardiovagal, and adrenergic domains. These findings raise the possibility that other autoantibodies may contribute to the pathogenesis of AAG.

Serologic profiles aiding the diagnosis of autoimmune gastrointestinal dysmotility

BACKGROUND & AIMS

Autoimmune gastrointestinal dysmotility is a limited autoimmune dysautonomia occurring idiopathically or in the context of an anatomically remote neoplasm, previously documented or unsuspected. Here we report 24 Mayo Clinic patients in whom the profile of serum autoantibodies aided this diagnosis.

METHODS

All patients were ascertained serologically in the course of service evaluation for autoantibodies consistent with neurologic autoimmunity. Review of their histories, motility studies, and laboratory findings revealed that all had presented with subacute gastrointestinal dysmotility.

RESULTS

Recorded motility abnormalities included esophageal dysmotility 8 (6 had achalasia), delayed gastric emptying 12, slow small intestinal transit 7, slow colonic transit 4, and pelvic floor dyssynergia 4. Four patients underwent abdominal surgery; 2 commenced total parenteral nutrition. Plasma membrane cation channel autoantibodies were detected in 23 patients: neuronal voltage-gated calcium channel (5 N-type and 1 P/Q-type), acetylcholine receptor (11 ganglionic-type and 4 muscle-type), and neuronal voltage-gated potassium channel autoantibodies (4). Two patients had antineuronal nuclear autoantibodies, type 1. Approximately half of the patients had neural autoantibodies (including skeletal muscle striational and glutamic acid decarboxylase, 65kd isoform) or other antibody markers of organ-specific autoimmunity (thyroid or gastric parietal cell specificities). Neoplasia was diagnosed in 11 patients (9 recent, 2 remote): lung, breast and endometrial, gastrointestinal and thymoma. Moderate to dramatic improvement in gastrointestinal symptoms was reported after immunotherapy in 4 of 4 patients treated and after pyridostigmine treatment in 2 of 2 patients treated.

CONCLUSIONS

Autoimmune serology aids the diagnosis of autoimmune gastrointestinal dysmotility, both paraneoplastic and idiopathic, and might guide management.

Paraneoplastic neurological syndromes and onconeural antibodies: clinical and immunological aspects

Paraneoplastic neurological syndromes (PNS) are infrequent disorders that are associated with cancer. The syndromes are highly heterogeneous and often affect several areas of the nervous system. Among the most well-known syndromes are paraneoplastic encephalomyelitis, cerebellar degeneration, sensory neuronopathy, and Lambert-Eaton myastenic syndrome. There are various associated tumors, in particular small cell lung cancer, cancer of the breast and ovary, and thymoma. The onset of neurological symptoms often precedes the cancer diagnosis, and the recognition of a paraneoplastic syndrome should lead to immediate search for cancer. The etiology of the paraneoplastic syndromes is believed to be autoimmune. Antibodies to onconeural antigens, expressed in the tumor of the affected individual and in normal neurons, are found in many of the patients. These antibodies are useful markers for paraneoplastic etiology. The pathogenesis of the PNS is uncertain, but cellular immune responses are thought to be the main effector mechanism. The cornerstone of therapy is the identification and treatment of the underlying malignancy. In some of the disorders, immunosuppressive therapy is of additional benefit. The prognosis of the different PNS varies depending on the level of affection and the degree of neuronal death.

Autonomic paraneoplastic neurological syndromes

Autonomic paraneoplastic neurological syndromes (PNS) typically present as chronic gastrointestinal pseudo-obstruction or orthostatic hypotension and usually occur in association with other PNS rather than in isolation. Although rare, they are often debilitating, sometimes fatal, and probably seriously underdiagnosed. Here, we discuss the clinical, immunological and oncological features of these syndromes and review the molecular and cellular mechanism that may underlie the triggering and maintenance of their autoimmune pathogenesis.

Autonomic peripheral neuropathy

The autonomic neuropathies are a group of disorders in which the small, lightly myelinated and unmyelinated autonomic nerve fibres are selectively targeted. Autonomic features, which involve the cardiovascular, gastrointestinal, urogenital, sudomotor, and pupillomotor systems, occur in varying combination in these disorders. Diabetes is the most common cause of autonomic neuropathy in more developed countries. Autonomic neuropathies can also occur as a result of amyloid deposition, after acute infection, as part of a paraneoplastic syndrome, and after exposure to neurotoxins including therapeutic drugs. Certain antibodies (eg, anti-Hu and those directed against neuronal nicotinic acetylcholine receptor) are associated with autonomic signs and symptoms. There are several familial autonomic neuropathies with autosomal dominant, autosomal recessive, or X-linked patterns of inheritance. Autonomic dysfunction can occur in association with specific infections. The availability of sensitive and reproducible measures of autonomic function has improved physicians' ability to diagnose these disorders.

Lambert-Eaton Myasthenic Syndrome

A high index of suspicion is essential in arriving at the correct diagnosis of Lambert-Eaton myasthenic syndrome (LEMS). LEMS should be considered in the differential in any patient who has proximal weakness, reduced or absent muscle stretch reflexes, and dry mouth. Weakness predominates in hip and shoulder muscles, but may also affect ocular and oropharyngeal muscles to a lesser extent. The diagnosis is confirmed by demonstrating characteristic electromyographic findings-low-amplitude muscle responses that increase dramatically after activation. Most patients also have circulating antibodies to the voltage-gated calcium channel. Half the patients with LEMS have a malignancy, usually small-cell lung cancer. The diagnosis should trigger an intensive search for malignancy, especially in older patients with a history of smoking. Younger, nonsmoking patients are likely to have LEMS as part of a more general autoimmune state. Successful treatment of the underlying cancer leads to improvement in many patients. More than 85% of patients have clinically significant benefit from 3,4-diaminopyridine (DAP). In over half of these, the improvement is marked. If severe weakness persists despite DAP, immunotherapy should be considered. Plasma exchange and high-dose immunoglobulin induce transient improvement in many patients, but function rarely becomes normal. Combinations of prednisone, azathioprine, or cyclosporine have been used with variable success. Improvement, if any, occurs only after many months and requires chronic administration of immunosuppressive medications at significant doses. The long-term prognosis in LEMS is determined by the presence of cancer or other autoimmune disease.

Efficacy of a half dose of oral pyridostigmine in the treatment of chronic fatigue syndrome: three case reports

Chronic fatigue syndrome (CFS) is characterized by persistent mental and physical fatigue for at least 6 months. Its pathophysiology is unknown and there is no proven effective treatment. We describe three cases who fulfill the criteria of CFS, in whom a defect of neuromuscular transmission and dysautonomia are present and who respond to acetylcholine-esterase inhibition. Case 1: 18-year-old female with a 3-year history of CFS. Response of compound-muscle-action potential, recorded using surface recording electrode, over left abductor pollicis brevis muscle, to repetitive nerve stimulation (RNS) at a rate of 10 Hz showed a 42% incremental response. Composite autonomic scoring system (CASS) showed mild cholinergic impairment (cardiovagal score: 1; sudomotor score: 2). Serological tests for Epstein-Barr virus (EBV) revealed positive antiviral capsid antigens (anti-VCA) immunoglobulins G (IgG). Oral pyridostigmine therapy (30 mg) resulted in marked improvement in symptoms. Case 2: 28-year-old female with 10-year history of CFS. RNS, using identical protocol, showed a 60% incremental response over the same muscle. CASS showed mild cholinergic impairment (cardiovagal score: 1; sudomotor score: 2) and this patient was also positive for EBV. This patient responded dramatically to 10-mg pyridostigmine. Case 3: 29-year-old female with a history of CFS for longer than 15 years. Repetitive stimulation, using identical paradigm to left abductor pollicis brevis muscle, showed a 42% incremental response. CASS showed mildly cholinergic impairment (cardiovagal score: 2; sudomotor score: 1). EBV antibody titers were positive. Patient responded to 30-mg pyridostigmine with an improvement in her fatigue. These three cases generate the hypothesis that the fatigue in some patients with clinical CFS might be due to a combination of mild neuromuscular transmission defect combined with cholinergic dysautonomia. Support for this thesis derives from the improvement with cholinesterase inhibition.

Neuromuscular complications of cancer

Neuromuscular complications of cancer are common and can affect any component of the peripheral nervous system from peripheral nerve cell body to muscle. Perhaps the most common complication is a length-dependent symmetric axonal polyneuropathy that is often multifactorial in etiology, resulting from metabolic and treatment effects of the primary malignancy. However, neuromuscular disorders may also be the presenting complaint in many conditions, including disorders caused by malignant infiltration of nerve and disorders cause by paraneoplastic syndromes. Although many of the paraneoplastic conditions are poorly responsive to treatment, not all are, and one hopes that prompt diagnosis of the underlying malignancy will lead to improved patient outcome. Recognition of iatrogenic neuromuscular complications is also important to modify treatment protocols when possible and thus decrease the risk of long-term neurologic disability.

Paraneoplastic neurologic syndromes

Cancer can affect the nervous system through many metastatic and nonmetastatic mechanisms, including side effects of cancer treatment, infections, coagulopathy, and metabolic or nutritional deficits. Paraneoplastic neurologic disorders (PND) are an extensive group of syndromes that cannot be explained by any of these complications and may affect any part of the nervous system. PND often develop before the presence of a cancer is known and their recognition may lead to the tumor diagnosis.

Lambert-eaton myasthenic syndrome: a case report and review of the literature

Lambert-Eaton myasthenic syndrome (LEMS) is a type of paraneoplastic syndrome that may initially manifest with weakness and gait abnormalities. These symptoms may precede the diagnosis of malignancy by months or years, and morbidity and mortality may be significantly affected by early detection of the malignancy. A case report and review of the diagnosis, management, and treatment of these syndromes are presented, with particular emphasis on the rehabilitation management of these patients, often overlooked in medical treatment.

Differences in clinical features between the Lambert-Eaton myasthenic syndrome with and without cancer: an analysis of 227 published cases

To compare the clinical features of patients with the Lambert-Eaton myasthenic syndrome (LEMS) associated with carcinoma, with patients having LEMS but no cancer, reports on LEMS patients were analyzed systematically. Cancer was detected (CD group) in 62% of the 227 included cases. This CD group showed a male predominance (70%). No sex difference was found in patients in whom no cancer was detected (NCD group). Median age at onset of LEMS in the CD group was higher than in the NCD group (58 and 49.5 years, P<0.01). Median interval between onset of symptoms and diagnosis of LEMS was longest in NCD cases (P<0.001). CD patients had additional immunological disorders less frequently than NCD cases (6 and 27%, P<0.001). Symptoms distinguishing the CD group from the NCD group were weight loss (P<0.001) and need for prolonged artificial ventilation after anaesthesia (P<0.05). This analysis shows significant differences between CD and NCD cases of LEMS. The male predominance and higher age at onset in patients with a tumor probably reflects the characteristics of patients with small cell lung cancer. The high frequency of additional immunological disorders in patients without malignancy, together with the younger age at onset suggests a similar etiology as other non-paraneoplastic autoimmune diseases.

Remote neurologic manifestations of cancer

Paraneoplastic disorders may affect any part of the central or peripheral nervous systems. Although relatively uncommon, these disorders are a significant cause of neurologic morbidity for cancer patients. At least some paraneoplastic syndromes are believed to be caused by an autoimmune reaction against shared tumor-neural antigens. This article summarizes the clinical features of paraneoplastic disorders, the current evidence for autoimmunity, and guidelines for diagnosis and treatment.

Autonomic dysfunction in Lambert-Eaton myasthenic syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder characterized by muscle weakness and autonomic dysfunction. Recent ex vivo and in vitro studies demonstrate that autoantibodies to the P/Q-subtype of voltage-gated calcium channel inhibit transmitter release from parasympathetic, sympathetic, and enteric neurons, a mechanism likely to underlie the widespread autonomic dysfunction in LEMS. This review summarizes clinical studies characterizing the autonomic symptoms and signs in LEMS and the effectiveness of treatment in alleviating these symptoms. Serological assays and in vitro pharmacologic and electrophysiologic studies are also discussed.

Myasthenia gravis with autoimmune autonomic neuropathy

The autoantibodies that impair neuromuscular junction transmission in myasthenia gravis are specific for the nicotinic acetylcholine receptor (AChR) of muscle. Antibodies specific for AChRs in ganglionic neurons are found in a majority of patients with subacute autonomic neuropathy. Dysautonomia is not a recognized feature of myasthenia gravis, but there have been rare reports of myasthenia gravis coexisting with autonomic failure, usually in association with thymoma. Here we report seven patients who had myasthenia gravis with subacute autonomic failure. Their autonomic dysfunction ranged from isolated gastroparesis to severe panautonomic failure. Gastrointestinal dysmotility was a common feature. All had antibodies against muscle AChR, and three (all of whom had thymoma) had antibodies against neuronal ganglionic AChRs. In several patients, gastrointestinal function improved clinically after administration of an acetylcholinesterase inhibitor. These observations support a rare but definite clinical association between myasthenia gravis and autonomic failure and strengthen the concept that subacute autonomic neuropathy is an autoimmune disorder.

Neurogenic bladder in Lambert-Eaton myasthenic syndrome and its response to 3,4-diaminopyridine

Autonomic dysfunction, as well as neuromuscular involvement, is a common manifestation of Lambert-Eaton myasthenic syndrome (LEMS). Dry mouth and impotence have been described as typical features of autonomic dysfunction, but neurogenic bladder is infrequent or subclinical in LEMS. We report a patient with neurogenic bladder secondary to LEMS whose condition responded to 3,4-diaminopyridine (3,4-DAP). In this patient's serum, results of repeated measurement with P/Q-type VGCC antibodies proved positive, but not with N-type VGCC and synaptotagmin antibodies. A review of the literature turned up a few patients with voiding dysfunction related to LEMS, but no urodynamic studies were done on these patients. Ours is the first case in which 3,4-DAP was efficacious in treating LEMS and neurogenic bladder. Responses of 3,4-DAP in urodynamic studies suggest that in this LEMS patient neurogenic bladder was caused by defective neurotransmission both in the autonomic detrusor and skeletal abdominal muscles.

Paraneoplastic syndromes of the spinal cord, nerve, and muscle

Cancer can affect the peripheral nervous system by non-metastatic, sometimes immune-mediated mechanisms. Recognition of these paraneoplastic syndromes is important because it can lead to the detection of the tumor, and also helps to avoid unnecessary studies to determine the cause of the neurologic symptoms in patients with cancer. Many paraneoplastic syndromes of the peripheral nervous system are not associated with serum antibodies that serve as markers of paraneoplasia. For this group of disorders the diagnosis depends on the clinician's index of suspicion and conventional electrophysiologic and laboratory tests. Treatment of the tumor, immunotherapy, or both may improve some of these syndromes. This review focuses on paraneoplastic syndromes of the spinal cord, peripheral nerve, and muscle.

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.