Peripheral Neuropathy

Micrograph showing a vasculitic peripheral neuropathy; plastic embedded; Toluidine blue stain

Peripheral neuropathy, often referred to simply as neuropathy, involves damage to the peripheral nerves, which can impair sensation, movement, gland function, and organ function. This condition can be acute or chronic, and may be reversible or permanent depending on the cause and severity.

Causes

Peripheral neuropathy has numerous causes, including systemic diseases like diabetes and leprosy, hyperglycaemia-induced glycation, vitamin deficiencies, certain medications (such as chemotherapy and some antibiotics), traumatic injuries, ischaemia, radiation therapy, excessive alcohol consumption, autoimmune diseases, celiac disease, non-celiac gluten sensitivity, and viral infections. It can also be genetic or idiopathic (with no known cause).

Classification

Peripheral neuropathy can be classified by the number and distribution of affected nerves, the type of nerve fibres involved, or the underlying process affecting the nerves.

Mononeuropathy

Mononeuropathy affects a single nerve and is often due to localised trauma or infection. Common examples include carpal tunnel syndrome and axillary nerve palsy.

Polyneuropathy

Polyneuropathy affects multiple nerves simultaneously, often symmetrically, and is usually more serious. Common causes include diabetes and inflammatory diseases. Symptoms often start in the feet and progress upward.

Mononeuritis Multiplex

Mononeuritis multiplex involves two or more nerves in different areas of the body. It often presents with asymmetric sensory and motor function loss, which may become more symmetric as the disease progresses.

Autonomic Neuropathy

Autonomic neuropathy affects the autonomic nervous system, impacting internal organs such as the bladder, cardiovascular system, and digestive tract. It is often seen in long-standing diabetes mellitus.

Signs and Symptoms

Symptoms depend on the type of nerve fibres affected. Sensory neuropathy symptoms include numbness, tingling, pain, and impaired balance, often starting in the feet. Motor neuropathy symptoms include muscle weakness, cramps, and fasciculations. Autonomic neuropathy can cause bladder incontinence, gastrointestinal issues, cardiovascular disturbances, respiratory impairments, and skin abnormalities.

Diagnosis

Diagnosis involves ruling out central nervous system lesions and conducting a detailed physical and neurological examination. Common diagnostic tests include electromyography (EMG) and nerve conduction studies (NCSs). For small-fibre neuropathies, tests like sweat tests, tilt table tests, and skin biopsies may be used. Blood tests can help identify underlying conditions like diabetes, vitamin deficiencies, and thyroid issues.

Treatment

Treatment varies based on the underlying cause. Managing the primary condition, such as diabetes, can significantly impact the course of neuropathy. Medications for symptom relief include tricyclic antidepressants, SNRIs, antiepileptics, and opioids.

Medications

The efficacy of medications for neuropathic pain varies. Antidepressants like amitriptyline and SNRIs such as duloxetine are commonly used, though evidence supporting their efficacy is mixed. Antiepileptics like gabapentin and pregabalin have shown some benefit, particularly for diabetic neuropathy. Opioids should be used cautiously due to their potential for dependence and side effects.

Medical Devices

Transcutaneous electrical nerve stimulation (TENS) therapy can provide symptom relief for diabetic neuropathy, though evidence quality varies. Surgical options, like nerve decompression, are considered in specific cases, especially for diabetic neuropathy.

Alternative Treatments

Dietary measures, such as a strict gluten-free diet for gluten-induced neuropathy, can be effective. Psychological therapies and alternative medicine approaches like acupuncture have shown mixed results and require further research.

Research

Emerging treatments like stem-cell therapy and further research into the association between celiac disease and peripheral neuropathy are ongoing. A strict gluten-free diet has been shown to be beneficial for gluten sensitivity-related neuropathy, regardless of the presence of enteropathy.

Self-assessment MCQs (single best answer)

Peripheral neuropathy involves damage to which part of the nervous system?

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Which of the following is a common cause of peripheral neuropathy?

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Mononeuropathy typically affects:

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Which diagnostic test is commonly used for small-fibre neuropathies?

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A common symptom of sensory neuropathy is:

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Which medication is often used for symptom relief in neuropathic pain?

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Autonomic neuropathy typically affects:

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What type of neuropathy involves two or more nerves in different areas of the body?

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Which dietary measure can be effective for gluten-induced neuropathy?

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What is the primary method for diagnosing peripheral neuropathy?

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