Lambert-Eaton myasthenic syndrome is one of the types of diseases that is extremely rare and has not yet been fully studied. Medicine recognizes the fact that an effective way to cure some types of myasthenic syndrome has not yet been found.
Diagnosis of these ailments is difficult, including due to the similarity of symptoms with its closest “relative” – myasthenia gravis.
In adults, myasthenic syndromes can develop as a complication of other dangerous diseases, including being precursors of oncology. Often, the presence of such a syndrome in a person is detected too late, already at the stage of loss of ability to work. In young children, congenital syndrome is most often detected.
The code for Lambert-Eaton syndrome according to the International Classification of Diseases ICD-10 is G-73.
Description
Lambert-Eaton syndrome was studied in detail by American researchers, in whose honor it received its eponymous name. This is myasthenic disease associated with autoimmune and neoplastic processes in the body. The age of those affected can vary from twenty to seventy years, but people over forty years of age are most often affected. At first, this syndrome was diagnosed mainly in men, and against this background the gender ratio was five cases of the disease in the stronger sex to one recorded disease in women. True, modern observations by specialists in the field of neurology have shown a decrease in this difference.
According to various sources, the described syndrome acts as a paraneoplastic disease in fifty to seventy-five percent of patients. It is especially common in men (about seventy percent of cases), and it occurs quite rarely in women. The overwhelming majority of all neoplasias that are diagnosed with this syndrome are small cell lung oncology. Moreover, the symptoms of myasthenic syndrome may precede the detection of tumor processes by several years. In a number of situations, the disease in question is combined with other paraneoplastic-type syndromes, for example, with paraneoplastic polyneuropathy.
General information
Eaton Lambert myasthenic syndrome is a rare autoimmune disease characterized by muscle weakness and muscle pain (myalgia). In 95% of cases, the disease affects the lower limbs and trunk. The upper body and eye muscles are practically unaffected.
In most cases, the patient is diagnosed with cancer in a malignant form. In general, for every one million healthy people there are up to four sick people.
There are two subtypes of the disease:
- Paraneoplastic (caused by the presence of a tumor).
- Autoimmune.
The majority of patients are male, but the disease has no age preference. Previously, it was believed that for every five sick men there was one sick woman; currently the difference is 70% to 30%. The age of patients ranges from 20 to 70 years with the largest surge (conventional surge) at the age of 40 years.
The disease was described by the American neurophysiologist Eaton Lambert, which is why this syndrome bears his name.
Causes of the disease
Lambert-Eaton syndrome can develop against the background of malignant neoplasia (cancer of the lung, stomach, ovaries, prostate, reticulosarcoma, etc.) or an autoimmune process (with rheumatoid arthritis, Sjögren's disease, autoimmune thyroiditis). The pathogenetic substrate of the disease is autoimmune mechanisms. Ninety percent of patients have antibodies to calcium channels, which are part of the structure of tumor cells and the endings of motor nerve fibers.
The causes of Lambert-Eaton syndrome are not fully understood. Presumably the main target of an autoimmune attack is the presynaptic membrane of the nerve muscle synapse. Its defeat leads to a decrease in the degree of release of acetylcholine, which is a mediator of nerve transmission. The result is a disruption in the process of passage of excitation from nerve fibers to muscle tissue, which can clinically manifest itself as fatigue and weakness.
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Symptoms of Lambert-Eaton syndrome
The basis of the clinical picture of the disease in question is the presence of increased fatigue and weakness of skeletal muscles, along with the predominant pathology in the upper extremities (hips and pelvic girdle). Patients, as a rule, complain about the presence of weakness in the legs and unsteadiness, this is especially noticeable when climbing stairs and during prolonged walking.
In addition, patients may experience discomfort in the back and neck along with myalgia, paresthesia in the distal extremities, and autonomic disorders (dry mouth, decreased tear production, development of distal hyperhidrosis and orthostatic arterial hypotension). A paretic duck gait is typical. A decrease in tendon reflexes is observed.
A distinctive feature of the described Lambert-Eaton syndrome is a slight increase in muscle strength during physical activity, in contrast to myasthenia gravis, against which any movements lead to worsening weakness. Some patients may experience noticeable drooping of the upper eyelids. Among other things, this syndrome is characterized by oculomotor disorders along with diplopia and swallowing disorders, although this is observed quite rarely.
Other forms of myasthenia gravis
The following forms of myasthenia gravis are distinguished.
Ptosis
The patient has double vision, the movement of the eyeballs is limited, the eyelids do not close completely. These symptoms are caused by damage to the muscles responsible for moving the eye and raising the eyelids.
Based on these symptoms, diagnosis of myasthenia gravis is possible in the early stages of development. The eyes are most often affected asymmetrically, that is, one at a time, and the eyelids can be affected simultaneously (left and right).
The visual defect, as a rule, disappears after a long rest and appears again with eye strain.
Myasthenia Gravis
Generalized myasthenia gravis is characterized by damage to the entire muscular system. The first signs of the disease:
- slight lethargy and weakness in the muscles, disappearing after rest;
- arms and legs become heavy and cease to obey;
- possible signs of ocular myasthenia;
- change in heart rate;
- increased salivation.
The danger of this pathology is that the disease can affect the respiratory muscles, resulting in a person dying from suffocation. It is very important to diagnose myasthenia gravis in time, only in this case it is possible to prevent its further development.
The disease can be identified by analyzing the patient’s medical history and through a comprehensive examination. Periods of crises and remission are typical for generalized myasthenia.
If the patient experiences a crisis (determined by the symptoms described above), an ambulance must be called immediately.
Before the doctors arrive, the patient needs to be provided with good access to fresh air, complete rest, and given medications to drink that lower blood pressure.
Diagnosis of Lambert-Eaton syndrome
The diagnosis is made by neurologists based on complaints, and in addition, based on a neurological examination and the result of electroneuromyography. As part of the neurological status, tetraparesis is detected with a special emphasis in the proximal leg. Hyporeflexia is quite likely along with mild dysmetria when performing a coordination test. A slight decrease in the palatal and pharyngeal reflexes cannot be ruled out.
Electroneuromyography determines a decrease in the amplitude of resting action potentials. A temporary increase in the M-response can also be recorded during voluntary muscle contraction or against the background of rhythmic electrical stimulation of the nerve with a frequency of over 10 Hz (the so-called burn-in phenomenon). When stimulated at a frequency of 3 Hz, a decrease in the height of the M-response is observed, which is typical for myasthenia gravis. An electrophysiological study differentiates this syndrome from myasthenia gravis, polymyositis, myopathy and other nervous pathologies.
Given that there is a very high probability that this disease has developed as a paraneoplastic syndrome, extensive screening of patients for neoplasia is recommended. A blood test for tumor markers is performed, as well as a number of the following procedures:
- Performing a computed tomography scan of the chest.
- Carrying out magnetic resonance imaging of the brain.
- CT or MRI of the spine.
- Performing an ultrasound analysis of the thyroid gland.
In the absence of results (when there is no neoplasia), repeated examination is indicated at an interval of six months. In order to confirm the autoimmune nature of the disease, an immunological study is prescribed.
Let's take a closer look at the treatment of Lambert-Eaton syndrome.
What drugs are used in therapy?
If the disease is autoimmune in nature, then treatment in most situations consists of drug therapy, including the use of the following drugs:
- Taking glucocorticosteroids that suppress the immune system.
- The use of drugs that provoke the production of acetylcholine (we are talking about acetylcholinesterase inhibitors like Pirdostigmine and Ipidacrine).
- Taking potassium salts.
- Carrying out pulse therapy, which consists of using hormones that are administered to patients initially in the maximum amount, and then the dosage is reduced each time.
Taking certain medications for Lambert-Eaton syndrome that trigger the production of acetylcholine carries a certain risk of side effects, for example:
- The appearance of convulsive processes.
- The occurrence of bradycardia.
- The presence of increased salivation.
- Constriction of the pupils along with the development of cramps in the stomach or intestinal area.
Therefore, the dosage of such medications should be selected and adjusted only by a doctor.
Immunosuppression
Some evidence supports the use of intravenous immunoglobulin (IVIG). Immune suppression is less effective than for other autoimmune diseases. Prednisolone (a glucocorticoid or steroid) suppresses the immune response; the steroid-sparing agent azathioprine can replace it once therapeutic effect is achieved. IVIG is used with some degree of effectiveness.
Plasma exchange (plasmapheresis), removal of plasma proteins such as antibodies, replacement with normal plasma, provides improvement in acute severe weakness. It is less effective than other related conditions such as myasthenia gravis and requires additional immunosuppressive treatment.
Treatment of the syndrome
In the presence of paraneoplastic genesis of this rare autoimmune disease, treatment is based on the elimination of tumor processes. If tumor therapy is successful, then, as a rule, regression of symptoms is observed. In the case of autoimmune genesis of the disease, symptomatic therapy is carried out with pharmaceutical drugs that have a depressing effect on the immune system. Mostly, as noted above, glucocorticosteroids are used. A good effect is demonstrated by plasmapheresis, which makes it possible to filter autoantibodies that circulate in it from the blood.
In order to facilitate muscle conduction, the treatment regimen includes acetylcholinesterase inhibitors, which are pharmaceutical drugs that facilitate nerve transmission through the accumulation of acetylcholine in the synapse. Such drugs include Pyridostigmine with Ipidacrine. In a number of situations, improvement is noted with the use of Guanidine, which facilitates the release of acetylcholine through nerve endings.
True, Guanidine has not found wide use due to its high toxicity with side effects on the kidneys and bone marrow. A less toxic drug with a similar effect is Diaminopyridine. Its use may be accompanied by the appearance of paresthesia, diarrhea, increased bronchial secretion and tachycardia. Despite the fact that the effectiveness of this medicine has been clinically proven, today it is used only in specialized medical centers. Next, let's talk about prevention methods.
Development mechanism
Through a synapse, impulses are carried out from neuron to neuron or to muscle cell.
In myasthenic syndromes, there are disturbances in the pre- and postsynaptic membranes of the synapse. Consequently, the conduction of the impulse is difficult. The signal from the nerve to the muscle is carried out using synapses. A synapse is a structural and functional formation between the axon terminal of a motor neuron (nerve cell) and the muscle fiber. The axon forms a thickening (plaque) at the end, which is covered with a presynaptic membrane. The mediator acetylcholine is synthesized and accumulated in the axon thickening. Myocyte cells that form muscle fibers are covered with a postsynaptic membrane. The postsynaptic membrane contains receptors for acetylcholine. Between these membranes is the synaptic cleft, where the enzyme acetylcholinesterase works, which breaks down acetylcholine. Signal transmission is carried out using acetylcholine, which is released from the axon thickening and binds to receptors on the postsynaptic membrane. Excess acetylcholine is broken down in the synaptic cleft by acetylcholinesterase. If in patients with myasthenia gravis antibodies block postsynaptic receptors, then in myasthenic syndromes there are defects in the presynaptic and postsynaptic membranes.
Presynaptic defects:
- Impaired synthesis and release of acetylcholine.
- Reduction of synaptic vesicles containing acetylcholine.
Postsynaptic defects:
- Acetylcholinesterase enzyme deficiency.
- Congenital deficiency of synaptic clefts.
- Acetylcholine receptor deficiency.
- Abnormal structure of receptors without a decrease in their number.
Preventive measures and possible consequences
The consequences of the syndrome in question can develop in the absence or against the background of untimely treatment of this disease. They can manifest themselves in the development of myasthenic crisis, which is very dangerous for the life and health of the patient. In such a crisis, patients may experience cardiac arrest, leading to death. It is very difficult to prevent this disease, as it can develop suddenly. But in order not to worsen the patient’s condition, one must adhere to the following doctor’s recommendations:
- Monitor physical activity, excluding excessive stress.
- Avoid prolonged exposure to direct sunlight.
- It is strictly forbidden to take certain medications based on magnesium and some other medications, which the doctor will definitely warn the patient about.
So, this syndrome is a rare and unpleasant disease, which in most cases develops together with malignant neoplasms. Therefore, you need to pay attention to this when diagnosing the underlying pathology.
Below is a brief instruction for use of Ipidacrine, used to treat the disease.
General information
Eaton Lambert myasthenic syndrome is a rare autoimmune disease characterized by muscle weakness and muscle pain (myalgia). In 95% of cases, the disease affects the lower limbs and trunk. The upper body and eye muscles are practically unaffected.
In most cases, the patient is diagnosed with cancer in a malignant form. In general, for every one million healthy people there are up to four sick people.
There are two subtypes of the disease:
- Paraneoplastic (caused by the presence of a tumor).
- Autoimmune.
The majority of patients are male, but the disease has no age preference. Previously, it was believed that for every five sick men there was one sick woman; currently the difference is 70% to 30%. The age of patients ranges from 20 to 70 years with the largest surge (conventional surge) at the age of 40 years.
The disease was described by the American neurophysiologist Eaton Lambert, which is why this syndrome bears his name.
Composition and release form
The medication is a solution for intramuscular administration and is also suitable for subcutaneous administration. The drug can also be presented in tablet dosage form. In each specific situation, the doctor individually determines the advisability of prescribing one or another format of the drug.
This medication is prescribed for various situations. For example, it is very effective for polyneuropathy, neuritis and polyneuritis, myasthenia gravis and myasthenic syndrome, bulbar palsy and paresis during the rehabilitation period, multiple sclerosis, Alzheimer's disease, encephalopathy, brain injuries of varying severity and against the background of disorders in cerebral circulation. But as noted earlier, this drug is especially useful in the presence of a clinical picture of Lambert-Eaton syndrome.
