MPA sensory peripheral neuropathy involves damage to the peripheral nerves, which are nerves outside the brain and spinal cord. This nerve damage primarily affects sensory functions, leading to various changes in sensation. The condition is directly linked to Microscopic Polyangiitis (MPA), an autoimmune disorder where the body’s immune system mistakenly attacks its own small blood vessels.
Understanding MPA Sensory Peripheral Neuropathy
Microscopic Polyangiitis (MPA) is an autoimmune vasculitis, a condition causing inflammation of blood vessels. In MPA, this inflammation targets the smallest blood vessels: capillaries, venules, and arterioles. The immune system produces abnormal proteins called anti-neutrophil cytoplasmic antibodies (ANCAs), which contribute to this inflammation.
When the small blood vessels supplying peripheral nerves become inflamed, they damage the nerves. This results in sensory peripheral neuropathy, affecting sensory nerves. Sensory nerves transmit information about touch, temperature, pain, and position from the body to the brain. Impaired blood supply due to vasculitis can injure these nerve fibers, leading to their dysfunction.
The damage in MPA sensory peripheral neuropathy stems from the autoimmune attack on blood vessels nourishing the nerves. This process, known as ischemic neuropathy, deprives nerves of oxygen and nutrients. Such deprivation leads to nerve fiber damage and loss, impacting signals sent to the brain. The resulting sensory deficits are characteristic of this condition.
Recognizing the Symptoms
Individuals with MPA sensory peripheral neuropathy experience various sensory symptoms. Numbness is frequent, often described as a loss of feeling in affected areas, typically starting in the feet and hands and progressing upwards. Tingling sensations, often described as pins and needles, are also common.
Pain is also a symptom, manifesting in several ways. People may report burning pain, which feels like a persistent heat sensation, sharp, shooting pains, or electric-shock like sensations, indicating nerve irritation. These pain symptoms can range from mild to severe.
Altered sensations are characteristic, where normal touch may feel unpleasant or painful. Light touch or pressure might be perceived as uncomfortable, known as allodynia. Symptoms can worsen over time if the underlying condition is not managed. Difficulty with balance or coordination can also arise due to sensory input loss from the feet and legs.
How it’s Diagnosed
Diagnosing MPA sensory peripheral neuropathy involves a comprehensive clinical evaluation. A healthcare provider takes a detailed history of the patient’s symptoms, including onset, progression, and characteristics. A neurological examination assesses sensory function, reflexes, and muscle strength. This initial assessment helps identify patterns consistent with peripheral nerve involvement.
Blood tests are important for identifying markers associated with MPA. Testing for anti-neutrophil cytoplasmic antibodies (ANCAs), specifically p-ANCA (myeloperoxidase-ANCA or MPO-ANCA), is key. Elevated levels of these antibodies suggest MPA. Other blood tests include inflammatory markers like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), often elevated in active vasculitis.
Nerve conduction studies (NCS) and electromyography (EMG) are specialized tests evaluating nerve and muscle function. NCS measures how quickly electrical signals travel along nerves, while EMG assesses muscle electrical activity. These tests identify the presence, type, and extent of nerve damage, helping differentiate sensory neuropathy from other neurological conditions. They can also reveal signs of nerve damage consistent with ischemia.
In some cases, a nerve biopsy may confirm the diagnosis. This involves taking a small nerve tissue sample, usually from the ankle, for microscopic examination. A biopsy can reveal inflammation of blood vessels within the nerve (vasculitis), nerve fiber damage, and signs of ischemic injury. Imaging studies, such as magnetic resonance imaging (MRI), may also rule out other causes of neurological symptoms or assess specific nerve involvement.
Treatment Approaches
Treating MPA sensory peripheral neuropathy involves suppressing underlying autoimmune inflammation and managing neuropathic symptoms. The goal is to halt the immune system’s attack on blood vessels, preventing further nerve damage. Immunosuppressive medications are central to this treatment.
Corticosteroids, such as prednisone, are often among the first medications prescribed to rapidly reduce inflammation. For severe cases, stronger immunosuppressants like cyclophosphamide may induce vasculitis remission. Rituximab, a biologic medication targeting specific immune cells, is another effective MPA treatment, particularly for achieving and maintaining remission. These medications dampen the overactive immune response, reducing blood vessel inflammation.
Managing neuropathic symptoms focuses on alleviating pain and improving sensory function. Medications for neuropathic pain, such as gabapentin or pregabalin, are commonly prescribed. These drugs modulate nerve signals that contribute to pain perception. Tricyclic antidepressants and serotonin-norepinephrine reuptake inhibitors (SNRIs) can also manage chronic neuropathic pain.
Physical therapy helps individuals regain strength, improve balance, and maintain mobility affected by sensory loss. Occupational therapy provides strategies and adaptive equipment to assist with daily activities challenged by numbness or altered sensation. These supportive therapies improve quality of life and functional independence while the underlying condition is treated.
Managing the Condition
Long-term management of MPA sensory peripheral neuropathy includes ongoing monitoring and supportive care. Regular follow-up appointments with a neurologist and rheumatologist assess disease activity and adjust medication dosages. This continuous oversight helps prevent relapses and manage persistent symptoms.
Lifestyle adjustments are also important for individuals with this condition. Meticulous foot care is important due to potential numbness, which can mask injuries or infections. Regularly inspecting feet for cuts, blisters, or sores can prevent serious complications. Fall prevention strategies, such as removing tripping hazards and using assistive devices, are important due to potential balance issues.
A multidisciplinary care team, including pain management physicians, physical therapists, and occupational therapists, provides comprehensive support. This collaborative approach addresses the varied challenges of nerve damage and autoimmune disease. Coping strategies, including support groups or counseling, also provide emotional support and practical advice for navigating the chronic nature of the condition.
—
Citations:
https://www.ninds.nih.gov/health-information/disorders/vasculitic-neuropathy
https://www.vasculitisfoundation.org/types/microscopic-polyangiitis/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8930438/
https://my.clevelandclinic.org/health/diseases/14737-peripheral-neuropathy
https://www.ninds.nih.gov/health-information/disorders/peripheral-neuropathy
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3574852/
https://www.vasculitisfoundation.org/education/forms-of-vasculitis/microscopic-polyangiitis/
https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/electromyogram-emg-and-nerve-conduction-studies-ncs
https://www.vasculitisfoundation.org/education/microscopic-polyangiitis-mpa/
https://www.uptodate.com/contents/microscopic-polyangiitis-clinical-manifestations-and-diagnosis
https://www.ninds.nih.gov/health-information/disorders/peripheral-neuropathy#toc-treatment
https://www.ninds.nih.gov/health-information/disorders/vasculitic-neuropathy#toc-treatment
https://www.ncbi.nlm.nih.gov/books/NBK560862/