Polyneuropathy are a heterogeneous group of diseases characterized by systemic damage to peripheral nerves. Disease are divided into primary axonal and primary demyelinating. Regardless of the type of polyneuropathy, its clinical picture is characterized by the development of muscle weakness and atrophy, a decrease in tendon reflexes, various sensitivity disorders (paresthesia, hypo- and hyperesthesia) occurring in the distal extremities, vegetative disorders. An important diagnostic point in establishing the diagnosis of polyneuropathy is to determine the cause of its occurrence. The treatment of polyneuropathy is symptomatic, the main task is to eliminate the causal factor.
Causes
Regardless of the etiological factor, two types of pathological processes are detected in this disease — axon damage and nerve fiber demyelination. With an axonal type of lesion, secondary demyelination occurs, with a demyelinating lesion, the axonal component is attached for a second time. The majority of toxic form are primarily axonal, axonal type of GBS, type II HMSN. Primary demyelinating polyneuropathy include the classical variant of GBS, CIDP, paraproteinemic polyneuropathy, type I HMSN.
In axonal polyneuropathy, the transport function of the axial cylinder suffers mainly, carried out by the axoplasmic current, which carries a number of biological substances necessary for the normal functioning of nerve and muscle cells in the direction from the motor neuron to the muscle and back. The nerves containing the longest axons are involved in the process first of all. A change in the trophic function of the axon and axonal transport leads to the appearance of denervation changes in the muscle. Denervation of muscle fibers stimulates the development of terminal, and then collateral sprouting, the growth of new terminals and reinnervation of muscle fibers, which leads to a change in the structure of the DE.
With demyelination, there is a violation of the saltatory conduction of the nerve impulse, as a result of which the speed of conduction along the nerve decreases. Demyelinating nerve damage is clinically manifested by the development of muscle weakness, early loss of tendon reflexes without the development of muscle atrophy. The presence of atrophy indicates an additional axonal component. Nerve demyelination can be caused by autoimmune aggression with the formation of antibodies to various components of the peripheral myelin protein, genetic disorders, exposure to exotoxins. Damage to the nerve axon may be caused by the effect of exogenous or endogenous toxins on the nerves, genetic factors.
Classification
To date, there is no generally accepted classification. According to the pathogenetic sign, pathology are divided into axonal (primary lesion of the axial cylinder) and demyelinating (pathology of myelin). According to the nature of the clinical picture, motor, sensory and vegetative form are distinguished. However, in its pure form, these forms are observed very rarely, more often they reveal a combined lesion of two or three types of nerve fibers (motor-sensory, sensory-vegetative, etc.).
According to the etiological factor, polyneuropathy are divided into hereditary (Charcot-Marie-Tuta neural amyotrophy, Russi-Levy syndrome, Dejerin-Sotta syndrome, Refsum disease, etc.), autoimmune (Miller-Flesher syndrome, axonal type of GBS, paraproteinemic polyneuropathy, paraneoplastic neuropathies, etc.), metabolic (diabetic polyneuropathy, uremic polyneuropathy , hepatic polyneuropathy, etc.), alimentary, toxic and infectious-toxic.
Symptoms
The clinical picture of polyneuropathy, as a rule, combines signs of damage to motor, sensory and vegetative fibers. Depending on the degree of involvement of fibers of various types, motor, sensory or vegetative symptoms may prevail in the neurological status. The defeat of motor fibers leads to the development of sluggish paresis, for most polyneuropathy, the defeat of the upper and lower extremities with a distal distribution of muscle weakness is typical, with prolonged axon lesions, muscle atrophy develops. Axonal and hereditary polyneuropathy are characterized by a distal distribution of muscle weakness (more often in the lower extremities), which is more pronounced in the extensor muscles than in the flexor muscles. With pronounced weakness of the peroneal muscle group, steppage develops (the so-called “cock’s gait”).
Acquired demyelinating polyneuropathy may manifest as proximal muscle weakness. In severe cases, there may be damage to the heart and respiratory muscles, which is most often observed in Guillain-Barre syndrome (GBS). Disease are characterized by relative symmetry of muscle weakness and atrophy. Asymmetric symptoms are characteristic of multiple mononeuropathies: multifocal motor neuropathy, multifocal sensorimotor neuropathy Sumner-Lewis. Tendon and periosteal reflexes in polyneuropathy usually decrease or fall out, first of all, the reflexes of the Achilles tendon decrease, with further development of the process — knee and carporadial, tendon reflexes from the biceps and triceps muscles of the shoulder can remain preserved for a long time.
Sensory disturbances in polyneuropathy are also most often relatively symmetrical, first occur in the distal parts (like “gloves” and “socks”) and spread proximally. At the onset of polyneuropathy, positive sensory symptoms (paresthesia, dysesthesia, hyperesthesia) are often detected, but with the further development of the process, the symptoms of irritation are replaced by symptoms of prolapse (hypesthesia). The defeat of thick myelinated fibers leads to violations of deep muscle and vibration sensitivity, the defeat of thin myelinated fibers leads to a violation of pain and temperature sensitivity of the skin.
Violation of vegetative functions is most pronounced in axonal polyneuropathy, since the vegetative fibers are unmyelized. Symptoms of prolapse are more often observed: the defeat of sympathetic fibers running as part of peripheral nerves is manifested by dryness of the skin, impaired regulation of vascular tone; the defeat of visceral vegetative fibers leads to dysautonomia (tachycardia, orthostatic hypotension, decreased erectile function, disruption of housing and communal services).
Diagnostics
When detecting a slowly progressing sensorimotor polyneuropathy that debuted from the peroneal muscle group, it is necessary to clarify the hereditary history, especially the presence of fatigue and weakness of leg muscles, gait changes, foot deformity (high elevation) in relatives. With the development of symmetrical weakness of the extensors of the hand, it is necessary to exclude lead intoxication. As a rule, toxic polyneuropathy are characterized, in addition to neurological symptoms, by general weakness, increased fatigue and rarely abdominal complaints. In addition, it is necessary to find out what medications the patient has taken / is taking in order to exclude drug polyneuropathy.
Slowly progressive development of asymmetric muscle weakness is a clinical sign of multifocal motor polyneuropathy. Diabetic polyneuropathy is characterized by slowly progressive hypesthesia of the lower extremities in combination with a burning sensation and other manifestations in the feet. Uremic polyneuropathy occurs, as a rule, against the background of chronic kidney disease (CRF). With the development of sensory-vegetative polyneuropathy, characterized by burning, dysesthesia, against the background of a sharp decrease in body weight, it is necessary to exclude amyloid polyneuropathy.
Hereditary polyneuropathy are characterized by the predominance of weakness of the extensor muscles of the feet, steppage, absence of Achilles tendon reflexes, high arch of the foot. In the later stage of the disease, there are no knee and carporadial tendon reflexes, atrophy of the muscles of the feet and shins develops. Muscle damage corresponding to the innervation of individual nerves, without sensory disturbances, is characteristic of multiple motor polyneuropathy. In most cases, the lesion of the upper extremities prevails.
Sensory polyneuropathy are characterized by distal distribution of hypesthesia. In the initial stages of the disease, hyperesthesia is possible. Sensorimotor axonal neuropathies are characterized by distal hypesthesia and distal muscle weakness. With vegetative polyneuropathy, both the phenomena of prolapse and irritation of autonomic nerve fibers are possible. For vibrational polyneuropathy, hyperhidrosis, vascular tone disorders of the hands are typical, for diabetic polyneuropathy, on the contrary, dry skin, trophic disorders, autonomic dysfunction of internal organs.
The study of antibodies to GM1-ganglycosides is recommended to be carried out in patients with motor neuropathies. High titers (more than 1:6400) are specific for motor multifocal neuropathy. Low titers (1:400-1:800) are possible in chronic inflammatory demyelinating polyradioloneuropathy, Guillain-Barre syndrome and other autoimmune neuropathies. It should be remembered that an increased titer of antibodies to GM1-ganglycosides is detected in 5% of healthy people (especially the elderly). Antibodies to myelin-associated glycoprotein are detected in 50% of patients diagnosed with paraproteinemic polyneuropathy and in some cases other autoimmune neuropathies.
If disease associated with intoxication with lead, aluminum, mercury are suspected, blood and urine tests are performed for the content of heavy metals. It is possible to carry out molecular genetic analysis for all major forms of HMHS I, IVA, IVB types. Conducting needle electromyography in polyneuropathy makes it possible to identify signs of the current denervation-reinnervation process. First of all, it is necessary to examine the distal muscles of the upper and lower extremities, and, if necessary, the proximal muscles. Nerve biopsy is justified only if amyloid polyneuropathy is suspected (detection of amyloid deposits).
Treatment
In hereditary polyneuropathy, treatment is symptomatic. In autoimmune form, the goal of treatment is to achieve remission. In diabetic, alcoholic, uremic and other chronic progressive polyneuropathy, treatment is reduced to reducing the severity of symptoms and slowing down the course of the process. One of the important aspects of non—drug treatment is physical therapy aimed at maintaining muscle tone and preventing contractures. In case of respiratory disorders with diphtheria polyneuropathy, a ventilator may be required. There is no effective medical treatment of hereditary form. Vitamin preparations and neurotrophic agents are used as maintenance therapy. However, their effectiveness has not been fully proven.
For the treatment of porphyritic polyneuropathy, glucose is prescribed, which usually causes an improvement in the patient’s condition, as well as painkillers and other symptomatic drugs. Drug treatment of chronic inflammatory demyelinating polyneuropathy includes membrane plasmapheresis, the use of human immunoglobulin or prednisone. In some cases, the effectiveness of plasmapheresis and immunoglobulin is insufficient, therefore, if there are no contraindications, treatment should immediately begin with glucocorticosteroids. Improvement usually occurs after 25-30 days; after two months, you can start gradually reducing the dose to maintenance. When reducing the dose of glucocorticosteroids, EMG monitoring is necessary. As a rule, it is possible to completely cancel prednisone within 10-12 months, if necessary, you can “hedge” with azathioprine (either cyclosporine or mycophenolate mofetil).
Treatment of diabetic polyneuropathy is carried out in conjunction with an endocrinologist, its main purpose is to maintain normal blood sugar levels. Tricyclic antidepressants, as well as pregabalin, gabapentin, lamotrigine, carbamazepine are used to relieve pain. In most cases, thioctic acid preparations and group B vitamins are used. Regression of symptoms at an early stage of uremic polyneuropathy is achieved by nephrologists when correcting the level of uremic toxins in the blood (program hemodialysis, kidney transplantation). B vitamins are used from medicines, tricyclic antidepressants, pregabalin are used for severe pain syndrome.
The main therapeutic approach in the treatment of toxic polyneuropathy is to stop contact with a toxic substance. In case of dose-dependent drug polyneuropathy, it is necessary to adjust the dose of the appropriate drug. With a confirmed diagnosis of diphtheria, the administration of antitoxic serum reduces the likelihood of developing diphtheria polyneuropathy. In rare cases, due to the development of contractures and deformities of the feet, surgical treatment may be necessary. However, it should be remembered that prolonged immobility after surgery can negatively affect motor functions.
Forecast
With chronic inflammatory demyelinating polyradiculoneuropathy, the prognosis for life is quite favorable. The mortality rate is very low, however, full recovery occurs very rarely. Up to 90% of patients with immunosuppressive therapy achieve complete or incomplete remission. At the same time, the disease is prone to exacerbations, the use of immunosuppressive therapy may be due to its side effects, leading to numerous complications.
With hereditary polyneuropathy, it is rarely possible to achieve an improvement in the condition, since the disease progresses slowly. However, patients, as a rule, adapt to their condition and in most cases retain the ability to self-care until the very late stages of the disease. In diabetic polyneuropathy, the prognosis for life is favorable, provided timely treatment and careful control of glycemia. Only in the later stages of the disease, a pronounced pain syndrome can significantly worsen the patient’s quality of life.
The prognosis for life in uremic polyneuropathy depends entirely on the severity of chronic renal failure. Timely program hemodialysis or kidney transplantation can lead to complete or almost complete regression of uremic polyneuropathy.
