Polyneuritis involves the simultaneous inflammation of multiple peripheral nerves, which are the nerves outside of the brain and spinal cord. It is a specific type of polyneuropathy, a broader term for any disease affecting multiple nerves. While all polyneuritis is a form of polyneuropathy, its defining feature is inflammation, which is not the cause of all polyneuropathies. This disorder disrupts the communication between the central nervous system and the rest of the body.
Identifying the Symptoms
Sensory symptoms frequently include numbness, tingling, or a “pins-and-needles” feeling. Individuals may also experience sharp, stabbing, or burning pains. Another sensory hallmark is allodynia, where a person feels pain from stimuli that are not normally painful, such as the light touch of clothing.
The condition can also cause muscle weakness, first noticed in the hands and feet. This weakness can lead to a loss of coordination, making fine motor skills difficult. Over time, there can be a loss of muscle mass (atrophy) and a reduction or absence of reflexes.
A defining characteristic of polyneuritis is the symmetrical presentation of these symptoms. This means that if symptoms appear in one foot, they are very likely to appear in the other foot in a similar way. This “glove and stocking” distribution is common, where the symptoms start in the longest nerves of the body—those reaching the feet and then the hands—and may progress upward into the legs and arms.
Underlying Causes
Autoimmune disorders are a prominent cause, where the body’s immune system mistakenly targets its own peripheral nerves. In conditions like Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP), the immune system attacks the myelin sheath. This damage, known as demyelination, disrupts the nerves’ ability to transmit signals effectively.
Infections from certain viruses or bacteria can also provoke polyneuritis. The inflammation may be a direct result of the infectious agent attacking the nerves or an indirect consequence of the body’s immune response. For example, Lyme disease, shingles, and hepatitis C are known to trigger nerve inflammation.
Metabolic and endocrine problems are another significant source of nerve issues. Diabetes is one of the most common causes of polyneuropathy worldwide; high blood sugar levels over time can damage both the nerves and the small blood vessels that supply them with nutrients. This leads to a toxic environment that can foster inflammation and nerve cell injury.
Nutritional deficiencies, particularly a lack of certain B vitamins such as B1 (thiamine) and B12, can also lead to polyneuritis. These vitamins are necessary for proper nerve function and maintenance, and their absence can result in damage to the myelin sheath and nerve axons. Finally, exposure to various toxins, including heavy metals like lead and mercury or certain medications like some chemotherapy drugs, can directly poison nerve cells and trigger an inflammatory response.
The Diagnostic Process
Diagnosing polyneuritis involves confirming nerve damage and identifying its underlying cause. The evaluation begins with a neurological examination where a physician assesses reflexes, muscle strength, coordination, and sensation. This initial assessment helps map the pattern of the symptoms and guides further testing.
To get a more detailed picture of nerve function, doctors often use electrodiagnostic tests. Nerve conduction studies (NCS) involve placing small electrodes on the skin to measure the speed and strength of electrical signals traveling through the nerves. Electromyography (EMG) is often performed at the same time and involves inserting a very fine needle electrode into a muscle to record its electrical activity both at rest and during contraction. Together, these tests can pinpoint which nerves are affected.
Blood tests are a fundamental part of the diagnostic workup, as they can reveal many of the root causes of polyneuritis. These tests can identify markers of autoimmune diseases, detect infections, check for vitamin deficiencies, and assess for metabolic issues like diabetes or kidney dysfunction. The results of these blood panels often provide the direct evidence needed to understand what is triggering the nerve inflammation.
In certain situations, a lumbar puncture, or spinal tap, may be performed. This procedure involves collecting a small sample of cerebrospinal fluid (CSF)—the fluid that surrounds the brain and spinal cord—to check for signs of inflammation. An elevated protein level in the CSF without a corresponding increase in white blood cells is a characteristic finding in conditions like Guillain-Barré syndrome.
Approaches to Treatment and Management
The treatment for polyneuritis is a two-pronged approach: addressing the underlying condition and managing the symptoms. The primary strategy is to target the root problem identified during diagnosis. Successfully treating the source of the inflammation can slow or halt the progression of nerve damage.
For polyneuritis caused by autoimmune disorders like CIDP, treatments are aimed at modulating the overactive immune system. This often involves the use of corticosteroids to reduce inflammation, or more targeted therapies such as intravenous immunoglobulin (IVIg) or plasma exchange (plasmapheresis). If the cause is a nutritional deficiency, treatment is straightforward and involves supplementing the deficient vitamins.
Symptom management focuses on pain and muscle weakness. Neuropathic pain can be managed with various medications, including certain antidepressants and anti-seizure drugs that are effective at calming overactive nerve signals. Physical and occupational therapy play a large role in management. Physical therapists help patients maintain muscle strength and improve balance, while occupational therapists can provide strategies and adaptive equipment to make daily tasks easier.