Polyneuropathy

Polyneuropathies are one of the most common and clinically heterogeneous groups of diseases of the peripheral nervous system.

• According to studies, the prevalence of polyneuropathies ranges from 1% to 7%, reaching 7-8% among people over 65 years of age.
• In the structure of lesions of the peripheral nervous system, their share exceeds 60%, and among neurological patients they account for up to a quarter of all referrals.

The disease can develop at any age, affecting both motor and sensory and autonomic fibers, which determines an exceptional variety of symptoms — from mild numbness in the fingers to persistent motor disorders that limit daily activity and ability to work.

What is polyneuropathy?

Polyneuropathy is a diffuse, symmetrical lesion of peripheral nerves, in which the pathological process is not limited to one nerve or one limb. The disease is based on damage to nerve fibers — either their myelin sheath (demyelinating type), or the axon itself (axonal type), or a combination of them.

The lesion may affect:

• sensitive fibers — with the development of numbness, burning, tingling, pain and coordination disorders;
• motor fibers — with the formation of muscle weakness and atrophy;
• vegetative fibers — with disorders of the function of internal organs, blood pressure, sweating.

Understanding exactly which type of fiber is affected and what is the mechanism of damage is key to choosing the right therapeutic strategy.

Classification and causes of polyneuropathies

Polyneuropathies are divided into several key features.

By type of flow:

• Acute — develop up to 4 weeks (for example, Guillain-Barre syndrome).
• Subacute — symptoms increase within 4-8 weeks.
• Chronic — develop and progress for more than 8 weeks.

By primary defeat:

• Sensory (sensitive) — pain, numbness, burning, loss of sensitivity.
• Motor (motor) — muscle weakness, atrophy.
• Sensorimotor.
• Vegetative — with a violation of vegetative functions (disruption of internal organs: pressure, sweating, pelvic organ function).

By etiology:

• Metabolic — the most frequent (diabetic polyneuropathy, uremic, on the background of liver disease and endocrine disorders).
• Toxic — alcohol, drug (including those caused by chemotherapeutic drugs), intoxication with heavy metals.
• Deficient — with a lack of B vitamins (especially B9, B12), as well as polyneuropathy induced by nitrous oxide (NO), due to inactivation of vitamin B12.
• Autoimmune — Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy (CVD), paraneoplastic polyneuropathies.
• Infectious — on the background of HIV, Lyme disease, etc.
• Hereditary — Charcot-Marie-Tooth disease, hereditary neuropathy with a tendency to paralysis from compression, hereditary amyloid polyneuropathy, Fabry disease, etc.
• Idiopathic — when the cause remains unidentified even after a complete diagnostic examination.

Some forms of peripheral neuropathies

In addition to diffuse symmetrical polyneuropathies, independent forms requiring a special diagnostic approach are distinguished in clinical practice:

• Sensory neuropathies (gangliopathies) are primary lesions of the bodies of sensory neurons in the spinal ganglia. Clinically manifested by gross sensitive ataxia, asymmetry of symptoms, early involvement of the hands with relative preservation of muscle strength. They are often associated with paraneoplastic processes and autoimmune diseases.
• Neuropathy of thin fibers is an isolated lesion of unmyelinated fibers responsible for pain, temperature sensitivity and autonomic innervation. It is characterized by intense burning pains, hyperesthesia and vegetative disorders. Standard ENMG may remain normal.
• Multiple mononeuropathies are multifocal, asymmetric lesions of two or more separate peripheral nerves. It is manifested by pain syndrome, sensory and motor disorders in the innervation zones of the affected nerves. It is most often associated with vasculitis, systemic diseases, infections or paraneoplastic processes.

Clinical manifestations

Symptoms of polyneuropathy can vary from minimal to severe, but most forms are based on common mechanisms.

Sensitivity disorders. Numbness, tingling, burning in the distal extremities — in the feet and hands. A characteristic lesion is of the "socks and gloves" type. As the progression progresses, pain, temperature and tactile sensitivity are lost, sensitive ataxia develops — instability when walking, especially in the dark.
Pain syndrome. Burning, shooting pains, sometimes resembling an electric shock. Pain can significantly reduce the quality of life and requires special therapeutic tactics.
Motor disorders. Muscle weakness occurs in the distal extremities, accompanied by a decrease or loss of tendon reflexes. With prolonged course, muscular atrophy and deformities of the feet are formed.
Autonomic disorders. The defeat of vegetative fibers is manifested by sweating disorders, fluctuations in blood pressure, gastrointestinal disorders (constipation, diarrhea), pelvic organ dysfunction.

Diagnostics

Modern diagnosis of polyneuropathies requires an integrated approach and high-tech equipment. The Center of Neuromuscular Pathology MCSC named after A.S. Loginov uses a full range of diagnostic methods:

1. Electroneuromyography (examination of nerve conduction function) is a key method to determine the type of lesion (axonal, demyelinating), its prevalence and severity. The study makes it possible to objectively assess the speed of the impulse through the nerves and identify subclinical changes in the early stages.
1. Electroneuromyographic phenomenon of the conduction block in multifocal motor neuropathy. 

2. Quantitative sensory testing — the method is used in case of suspected damage to thin fibers, when standard ENMG (examination of nerve conduction function) does not reveal pathology.
3. Ultrasound examination (ultrasound) of nerves — allows you to assess the structure of peripheral nerves, identify their thickening, local compression (for example, carpal tunnel syndrome), schwannomas and other changes.
4. Laboratory diagnostics (blood serum examination) includes a wide range of tests to identify the cause of polyneuropathy.
5. Examination of cerebrospinal fluid (lumbar puncture) — performed in case of suspected autoimmune (Guillain-Barre syndrome, CVD), paraneoplastic and infectious forms of polyneuropathy to identify protein-cell dissociation, antibodies and inflammatory markers.
6. Molecular genetic diagnosis - in case of suspicion of hereditary forms of polyneuropathy.
7. Neuroimaging — to clarify the nature of the lesion and exclude other causes:

• MRI of the brachial and lumbosacral plexuses is performed if inflammatory (CVD, vasculitic neuropathies, plexitis) or tumor lesions of the plexuses are suspected.;

Figure 2. MRI of the brachial plexus in Lewis–Sumner syndrome (MADSAM). On the T2-VI with suppression of the fat signal (STIR), a pronounced hyperintensive signal of the brachial plexus trunks is determined on the right (indicated by the arrow).

• MRI of the spinal cord — to exclude compression, inflammatory or demyelinating lesions, as well as in case of suspected funicular myelosis caused by vitamin B deficiency₁₂;

3. MR-picture of funicular myelosis (vitamin B₁₂ deficiency). On the T2-weighted image in the axial projection, a symmetrical increase in the hypersign in the region of the posterior cords of the spinal cord is determined (a symptom of the "inverted letter V"), characteristic of demyelination against the background of cobalamin deficiency.

• MRI of the brain is performed in the presence of ataxia, cognitive impairment, suspected paraneoplastic syndromes or concomitant damage to the central nervous system.

Treatment

Treatment of polyneuropathies is always personalized and depends on the established cause, type of lesion and severity of the condition. 

Etiotropic therapy — effects on the cause of the disease: correction of glucose levels in diabetes mellitus, replenishment of vitamin deficiency, rejection of toxic substances, treatment of the infectious process, antitumor therapy for paraneoplastic syndromes.

Immunosuppressive and immunomodulatory therapy — for autoimmune forms (Guillain-Barre syndrome, CVD, paraneoplastic polyneuropathies): glucocorticosteroids, intravenous immunoglobulins, plasmapheresis.

Symptomatic therapy is aimed at relieving neuropathic pain using first—line drugs (anticonvulsants, antidepressants with proven efficacy).

Physical rehabilitation — physical therapy to maintain muscle strength, prevent contractures and maintain physical activity.

Multidisciplinary approach — management of patients with severe and combined forms of polyneuropathies is carried out jointly with doctors of related specialties — rehabilitologists, endocrinologists, rheumatologists, oncologists, gastroenterologists, geneticists and cardiologists, which allows for comprehensive treatment and continuous monitoring.

To consult a neurologist, conduct electromyography and prescribe therapy, you can contact the Center for Neuromuscular Pathology MCSC named after A.S. Loginov.
Conducting a comprehensive examination and receiving pathogenetic treatment is possible during hospitalization in the neurological department of the MCSC named after A.S. Loginov.

Make an appointment for a consultation, a study of nerve conduction function at the Center for Neuromuscular Pathology: +7 (495) 304-30-39.