Autonomic dysfunction and Eaton Lambert syndrome

Pupil abnormalities in selected autonomic neuropathies

Examination of the pupil provides an opportunity to detect disturbances in the autonomic innervation of the eye. The pupil is frequently affected in patients with generalized autonomic neuropathies. This literature review confirms a high prevalence of sympathetic deficits and parasympathetic deficits in acute or subacute dysautonomia, diabetes, amyloidosis, pure autonomic failure, paraneoplastic syndromes, Sjögren syndrome, familial dysautonomia, and dopamine beta-hydroxylase deficiency. It confirms the relative scarcity of a pupil abnormality in patients with multiple system atrophy. There are difficulties in clinical diagnosis of pupil abnormalities and interpretation of pupil pharmacologic tests, particularly when combined sympathetic and parasympathetic deficits are present.

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.

Lambert-Eaton myasthenic syndrome with ophthalmoparesis and pseudoblepharospasm

We report a patient initially diagnosed as having ocular myasthenia gravis who showed progressive ophthalmoparesis and pseudoblepharospasm together with positive acetylcholine receptor antibodies. Repeated evaluation with high-frequency repetitive stimulation revealed an incremental response and elevated titers of antibodies against presynaptic calcium channels, confirming Lambert-Eaton myasthenic syndrome. Systemic evaluation revealed no malignant neoplasm but revealed euthyroid Hashimoto's disease. Immunomodulative therapy including plasma exchange and administration of an immunosuppressent (azathioprine) combined with a potassium-channel blocker (3,4-diaminopyridine) reduced the ocular abnormalities. We conclude that the ocular manifestations in this patient were probably caused by Lambert-Eaton myasthenic syndrome.

Functional evaluation of inhibition of autonomic transmitter release by autoantibody from Lambert-Eaton myasthenic syndrome

The effects of the anti-voltage-gated Ca2+ channel (VGCC) antibody obtained from patients with Lambert-Eaton myasthenic syndrome (LEMS) on autonomic neurotransmission were studied in in-vitro experiments. The releases of acetylcholine (ACh) and norepinephrine from the autonomic nerves were evaluated by changes in the contractile responses of guinea pig taenia caeci and left atria to electric field stimulation, respectively. Incubations for 6 hours with LEMS serum and IgG, both of which contain anti-VGCC antibody, markedly suppressed the parasympathetic response but did not affect the sympathetic response. Pharmacological experiments with specific blockers to the VGCC subtypes showed that the Q-type VGCC is closely linked to the genesis of the parasympathetic response. We suggest that the anti-VGCC antibody from the LEMS patients specifically reduces the ACh release from the parasympathetic nerve by binding to the Q-type VGCC.

Lambert-Eaton syndrome antibodies inhibit acetylcholine release and P/Q-type Ca2+ channels in electric ray nerve endings

1. The types of voltage-dependent calcium channels (VDCCs) present in the cholinergic terminals isolated from the electric organ of the ray, Narke japonica, were characterized on the basis of their pharmacological sensitivity to specific antagonists. Inhibition of these channel types by autoantibodies from patients with the Lambert-Eaton syndrome (LES) was then studied to determine the specificity of the pathogenic IgG. 2. In normal untreated synaptosomal preparations, maximal doses of N- and P and/or Q-type Ca2+ channel antagonists, omega-conotoxin GVIA and omega-agatoxin IVA, inhibited depolarization-evoked ACh release by 47 % and 43 %, respectively. Calciseptine, an L-type VDCC antagonist, caused a 20 % reduction in the release. This indicates that the exocytotic release process is predominantly mediated by N- and P/Q-type VDCCs. 3. LES IgG or sera caused an inhibition of ACh release by 39-45 % in comparison with the control antibody-treated preparations. The ionomycin-induced ACh release, however, was not altered by the antibodies. Additionally, the same LES antibodies inhibited whole-cell calcium currents (ICa) in bovine adrenal chromaffin cells. Thus, the pathogenic antibodies exert their action on VDCCs present in the synaptosomes. 4. The efficacy of three Ca2+ channel antagonists in blocking ACh release was determined in preparations pretreated with LES IgG. omega-Agatoxin IVA produced only an additional 3-5 % reduction in release beyond that obtained with LES antibodies. Despite the pretreatment with LES IgG, omega-conotoxin GVIA and calciseptine inhibited the release to nearly their control levels. 5. These results indicate that LES antibodies mainly downregulate P/Q-type Ca2+ channels which contribute to presynaptic transmitter release from the cholinergic nerve terminals of electric organ. 6. The present findings are consistent with the hypothesis that P/Q-type VDCCs at the neuromuscular junction are the target of LES antibodies and that their inhibition by the antibodies produces the characteristic neuromuscular defect in this disease.

Autonomic neuropathy, II: Specific peripheral neuropathies

Autonomic dysfunction is a common complication of peripheral neuropathies. It is often of little clinical importance, but some conditions may cause profound disturbance of autonomic function. These conditions include acute dysautonomia, diabetes, primary and familial amyloidosis, Guillain-Barré syndrome, porphyria, and some inherited neuropathies. A wide range of neuropathies are associated with lesser degrees of autonomic dysfunction. These include hereditary neuropathies, and neuropathies associated with metabolic disturbances, alcohol abuse, malignancy, medications, infections, and connective tissue disorders.

Postganglionic cholinergic dysautonomia with incomplete recovery: a clinical, neurophysiological and immunological case study

A 26-year-old man presented with signs and symptoms of marked postganglionic cholinergic autonomic dysfunction manifested by non-reacting dilated pupils, paresis of accommodation, decreased salivation, dry skin, atony of the bladder, erectile impotence and complete gastrointestinal paresis. Standard neurophysiological tests for myelinated sensory and motor fibre function and quantitative methods to examine unmyelinated parasympathetic, sympathetic and afferent fibres were performed: parasympathetic function was measured by heart rate variation tests. Sympathetic cutaneous vasoconstrictor responses induced by deep inspiration were examined with laser Doppler flowmetry. Cutaneous nociceptive C-fibre function was assessed by measurement of axon reflex vasodilatation and flare size induced by histamine iontophoresis. The findings confirmed that the abnormalities were restricted exclusively to the cholinergic postganglionic autonomic systems. All other functions were completely preserved. Modern neurophysiological methods of testing sympathetic and afferent small fibre function might help in the diagnosis of cholinergic postganglionic dysautonomia in the early stages. The specificity of the dysfunction argues in favour of an immunological pathogenesis. However, antibody screening including acetylcholine receptor antibodies and voltage-gated calcium channel antibodies gave negative results. Whatever autoimmunological mechanism might be involved, the postulated antibodies act highly specifically on unknown structures of the cholinergic postganglionic autonomic neurons.

Cardiovascular autonomic insufficiency in a patient with metastatic malignancy

A case of cardiovascular autonomic insufficiency is described in a cachectic 70-year-old man with widely metastatic small-cell tumor. The patient experienced disabling syncopal episodes in association with severe postural hypotension. Tests of cardiovascular autonomic insufficiency were abnormal. The introduction of fludrocortisone and the use of elastic stockings produced palliation of the symptomatology, but his condition deteriorated and he died. Autopsy demonstrated unexpectedly extensive tumor invasion of autonomic nervous tissue. Although cardiovascular autonomic insufficiency (CAI) has been described in association with malignancy and malnutrition, local tumor invasion of autonomic nervous tissue and radiation injury may have been other possible, albeit unusual, etiologic factors. This case illustrates the differential diagnosis of hypotension and CAI in patients with advanced metastatic malignancy and also emphasizes the need for autopsy studies when speculating as to the cause of CAI in this group of patients.

Lambert-Eaton syndrome: antigen-antibody interaction and calcium current inhibition in chromaffin cells

Plasma and IgG obtained from 10 Lambert-Eaton myasthenic syndrome (LES) patients (5 with carcinoma, 5 without associated cancer), 6 healthy subjects, and 1 patient with small-cell lung cancer (SCLC) were examined in their ability to recognize chromaffin cell antigens on Western blots. The pattern of antigen recognition was compared with the magnitude of inhibition of voltage-dependent calcium and sodium currents recorded with the patch-clamp technique from chromaffin cells. Eight of the 11 patients with LES and/or SCLC recognized plasma membrane proteins and 9 of the patients' IgG interacted with cytoplasmic antigens with no apparent pattern of antigen recognition between patients. Also, there was no obvious band pattern distinguishing patients with LES from those with LES and concurrent SCLC. Eighty percent of the LES patients' antibodies were capable of reducing the calcium current (ICa) in chromaffin cells. One of the novel findings of this study is that 30% of the patients had produced antibodies which were able to inhibit both calcium and sodium currents (INa). The heterogeneous response of the IgG on the Western blots does not appear to correlate with the efficacy of reducing the inward currents.

Deficiency of sympathetic nervous system function in myasthenia

The norepinephrine (NE) and epinephrine (E) responses to forearm ischemia were studied in 24 myasthenic patients and 22 subjects with lumbar disc disease (control group). In some of these myasthenic (11 cases) and control (11 cases) subjects the NE and E responses to orthostasis were also investigated. In controls both stimuli induced a rise in NE urinary excretion without significantly changing the E excretion. On the other hand, in myasthenic patients forearm ischemia and orthostasis were followed by an augmentation in E excretion, the NE excretion remaining unchanged or even undergoing a depression. In other myasthenic patients (10 cases) and subjects with lumbar disc disease (10 cases) NE and E responses to exercise were tested. The results were similar to those presented above: controls reacted to exercise by a rise in NE excretion, while myasthenic patients, by an augmentation in E excretion; the NE excretion underwent no change or even decreased after exercise in myasthenia. The obliteration of NE response to all three testing stimuli found in myasthenic patients may be considered as a sign of their sympathetic deficiency. In such patients the normal E discharge produced by forearm ischemia, orthostasis or exercise may be interpreted as a compensatory reaction, being probably the consequence of sympathetic deficiency. The noradrenergic deficit of myasthenic patients is ascribable to their cholinergic hyperactivity.

Lambert Eaton syndrome: autonomic neuropathy and inappropriate antidiuretic hormone secretion in a patient with small cell carcinoma of the lung

A patient with small cell carcinoma of the lung developed asymptomatic autonomic neuropathy, inappropriate antidiuretic hormone (ADH) secretion and Lambert Eaton myasthenic syndrome. The autonomic neuropathy and inappropriate ADH secretion were present at the time of diagnosis of the tumour. Following chemotherapy these resolved, but 5 months later the patient developed Lambert Eaton syndrome which responded to 3,4-diaminopyridine. This sequence of changes appears to be unique.

Ocular autonomic nerve function in Lambert-Eaton myasthenic syndrome

Autonomic innervation to the eye and ocular adnexae was assessed in seven patients with Lambert-Eaton Myasthenic Syndrome and 50 age-matched control subjects. Pupil responses to light were abnormal in 69% of LEMS patients, compared with 18% of the control group. Reflex tear production--a screening test for parasympathetic innervation to the lacrimal gland--was below the accepted normal limit in 69% of LEMS patients. Parasympathetic and sympathetic denervation hypersensitivity of the iris musculature were individually present in 57% of LEMS patients, compared with 6% of control subjects. The association between autonomic dysfunction and Lambert-Eaton Myasthenic Syndrome is discussed.

Specificity of calcium channel autoantibodies in Lambert-Eaton myasthenic syndrome

Autoantibodies that interfere with neurotransmitter release by affecting the function of voltage-operated calcium channels (VOCCs) have been found in patients with Lambert-Eaton myasthenic syndrome (LES). To find out the nature of the antigen to which these autoantibodies bind, tests were done with omega-conotoxin, which blocks some types of VOCCs. LES antibodies were able to immunoprecipitate VOCCs prepared from the human neuronal cell line IMR32 which were pre-labelled with the specific VOCC ligand omega-conotoxin. LES autoantibodies are also able to specifically down-regulate the expression of VOCCs in IMR32 cells. A new radioimmunoassay for the quantitative detection of LES antibodies was developed and found to be of value in distinguishing LES patients from patients with myasthenia gravis and some other neurological disorders.

Acute autonomic and sensory neuropathy: report of an autopsy case

A 46-year-old woman presented acute sensorimotor neuropathy of the Guillain-Barré type, followed by a protracted course of profound autonomic and sensory dysfunction. Tests of autonomic functions showed denervation hypersensitivity. Neuropathologically, the trigeminal sensory nuclei, solitary nucleus, the dorsal columns of the spinal cord and dorsal spinal roots showed severe degeneration. Degeneration was found both in the preganglionic (intermediolateral cell columns of the spinal cord) and postganglionic (sympathetic ganglion and celiac ganglion) neurons of the sympathetic nervous system, and the preganglionic (dorsal motor nucleus of the vagus) and postganglionic (Auerbach's plexus) neurons of the parasympathetic nervous system.

Autonomic dysfunction in Lambert-Eaton myasthenic syndrome

Autonomic symptoms were observed in 6 patients with clinically and electrophysiologically documented Lambert-Eaton myasthenic syndrome (LEMS). Of the 6 patients, 2 were extensively investigated in the laboratory. In contrast to previous reports which recognized only cholinergic dysautonomia, abnormalities of sympathetic as well as parasympathetic function were evident. Of the 6 patients, 4 had small cell lung cancer (SCLC). In one male patient, chemotherapy for SCLC resulted in an early improvement of autonomic dysfunction and the electrophysiological defect, documenting simultaneous regression of dysautonomia and LEMS. In addition, the patients with SCLC and LEMS had a survival thus far of 3-13 years suggesting that a subgroup of SCLC patients have a better prognosis.

Abnormalities of autonomic function in the Lambert Eaton myasthenic syndrome

Two cases of Lambert Eaton syndrome unassociated with an underlying malignancy are described. Both had mild autonomic symptoms but markedly abnormal autonomic function tests. These results are suggestive of a widespread defect in cholinergic transmission in addition to that at the skeletal neuromuscular junction.

IgG from patients with Lambert-Eaton syndrome blocks voltage-dependent calcium channels

Lambert-Eaton syndrome, an autoimmune disorder frequently associated with small-cell carcinoma of the lung, is characterized by impaired evoked release of acetylcholine from the motor nerve terminal. Immunoglobulin G (IgG) antibodies from patients with the syndrome, applied to bovine adrenal chromaffin cells, reduced the voltage-dependent calcium channel currents by about 40 percent. When calcium was administered directly into the cytoplasm, however, the IgG-treated cells exhibited normal exocytotic secretion, as assayed by membrane capacitance measurement. Measurement with the fluorescent calcium indicator fura-2 indicated that the IgG treatment reduced potassium-stimulated increase in free intracellular calcium concentration. The pathogenic IgG modified neither kinetics of calcium channel activation nor elementary channel activity, suggesting that a reduction in the number of functional calcium channels underlies the IgG-induced effect. Therefore, Lambert-Eaton syndrome IgG reacts with voltage-dependent calcium channels and blocks their function, a phenomenon that can account for the presynaptic impairment characteristic of this disorder.