Arthritis is characterized by inflammation and damage within the joints, causing pain, stiffness, and reduced mobility. Peripheral neuropathy involves damage to the peripheral nerves, which transmit signals between the central nervous system and the rest of the body, often leading to numbness, tingling, and weakness in the hands and feet. The two conditions are frequently linked because the inflammatory processes and structural changes associated with arthritis can directly interfere with nerve function, leading to nerve damage.
Mechanisms Linking Joint Inflammation to Nerve Damage
Arthritis contributes to nerve damage through two primary pathways: localized mechanical compression and systemic inflammation.
Mechanical Compression
This pathway involves physical pressure on the nerves, a common consequence of joint degeneration and swelling. Compression occurs when inflamed or damaged joint tissues physically pinch a nearby nerve, impeding signal transmission. Joint swelling, accumulation of synovial fluid, or the growth of bone spurs (osteophytes) can narrow the space a nerve travels through. For example, inflammation in the wrist joint can compress the median nerve, resulting in Carpal Tunnel Syndrome, a common form of entrapment neuropathy. Joint destruction or partial dislocation (subluxation) can also cause misalignment that traps nerves against bone or tissue. This form of neuropathy is typically localized near the affected joint.
Systemic Inflammation
The second mechanism involves systemic inflammation, where the body’s overactive immune response directly attacks the nerves. In autoimmune arthritis, widespread inflammation can lead to vasculitis, which is the inflammation of blood vessels. When vasculitis affects the small blood vessels supplying the nerves (vasa nervorum), it starves the nerve of oxygen and nutrients. This causes widespread nerve damage known as polyneuropathy, which is often more severe than localized compression. The resulting damage can include destruction of the protective myelin sheath, slowing or blocking signal transmission.
Identifying High-Risk Arthritis Types
The risk of developing neuropathy varies depending on the specific type of arthritis.
Rheumatoid Arthritis (RA)
Rheumatoid Arthritis (RA) carries a high risk because it utilizes both the compressive and systemic inflammatory pathways. As an autoimmune condition, RA’s chronic, widespread inflammation can lead to vasculitis-related nerve damage throughout the body, resulting in true peripheral neuropathy. This systemic inflammation also causes significant joint swelling, leading to localized nerve entrapment syndromes in areas like the wrists and ankles.
Osteoarthritis (OA)
Osteoarthritis (OA) primarily causes neuropathy through the mechanical compression pathway. OA involves the breakdown of cartilage and the formation of bone spurs, particularly in the spine. These structural changes narrow the channels through which nerve roots exit the spinal column, leading to radiculopathy. Lumbar radiculopathy, a pinched nerve in the lower back, often presents as sciatica, with pain and numbness radiating down the leg.
Other Autoimmune Conditions
Other autoimmune conditions, such as Psoriatic Arthritis and Systemic Lupus Erythematosus (Lupus), also pose a risk due to their systemic inflammatory nature. Uncontrolled inflammation in these diseases can directly damage nerve tissue through vasculitis or other autoimmune processes.
Recognizing Symptoms and Confirming Diagnosis
Symptoms
The symptoms of peripheral neuropathy typically begin in the farthest reaches of the body, such as the hands and feet. Patients often describe sensations like numbness, tingling, or “pins and needles,” which can progress to burning or stabbing pain. This characteristic distribution, known as a “glove and stocking” pattern, occurs because the longest nerves in the body are the most vulnerable to damage. If motor nerves are affected, a patient may also experience muscle weakness, loss of coordination, or difficulty walking.
Diagnosis
Diagnosing arthritis-related neuropathy involves a thorough physical examination to assess reflexes, sensation, and muscle strength. Physicians often use electrodiagnostic tests to confirm the presence and type of nerve damage.
- A Nerve Conduction Study (NCS) measures how quickly electrical signals travel through the nerves, helping identify demyelination or nerve compression.
- Electromyography (EMG) is performed alongside NCS to evaluate the electrical activity of the muscles, determining if weakness is due to nerve injury or muscle disease.
- Blood tests are performed to measure inflammatory markers and rule out other common causes of neuropathy, such as diabetes or vitamin B12 deficiency.
Consulting with a specialist, such as a rheumatologist or a neurologist, is important for ensuring an accurate diagnosis and appropriate treatment plan.