Peripheral neuropathy: causes, patterns, symptoms and management

Typical patterns and symptoms

Clinicians describe peripheral neuropathy by pattern and by which nerve fibers are involved. The major patterns are:

• Polyneuropathy: a symmetrical, often length-dependent process that commonly begins in the toes and feet and progresses upward; patients first notice sensory changes in the feet — see foot symptoms.
• Mononeuropathy: isolated damage to a single nerve (for example carpal tunnel affecting the median nerve).
• Mononeuritis multiplex: injury to several individual nerves in different parts of the body, often due to vasculitis or inflammatory conditions.
• Autonomic neuropathy: selective involvement of autonomic fibers causing cardiovascular, gastrointestinal, urinary or sexual dysfunction.

Sensory nerve involvement commonly produces numbness, reduced vibration sense, tingling or painful sensations described as burning, electric-like or freezing; such discomfort is often termed neuropathic pain and can be severe. Motor involvement causes muscle weakness, cramps, loss of muscle bulk and twitching. When autonomic fibers are affected, patients may experience problems such as abnormal heart rate responses, orthostatic blood pressure changes, bladder or bowel dysfunction and sexual difficulties including erectile or arousal problems (sexual dysfunction may be reported).

Causes and risk factors

A broad range of underlying causes exist. The most common identified systemic cause is diabetes mellitus, but neuropathy also occurs with alcohol misuse, certain vitamin deficiencies, chronic kidney disease, autoimmune diseases, infections (for example Lyme disease or post-viral syndromes), inherited neuropathies, exposure to toxins or some chemotherapy agents. Neuropathy may accompany or follow other illnesses and sometimes remains idiopathic despite investigation. Diabetes-related neuropathy occurs both in people with long-standing and, less commonly, newly diagnosed diabetes; see diabetes resources.

Diagnosis and investigations

Evaluation begins with a medical history and focused neurological examination assessing sensation, muscle strength, reflexes and autonomic signs. Bedside tests are complemented by laboratory studies directed at suspected causes (glucose, renal and liver tests, vitamin levels, autoimmune markers). Electrophysiological studies such as nerve conduction studies and electromyography help define whether neuropathy is primarily axonal or demyelinating and whether small or large fibers are involved. Skin biopsy and autonomic testing are available for some forms. Imaging or nerve biopsy are reserved for selected cases.

Treatment, prognosis and key facts

Management targets the cause when possible (glycemic control, vitamin repletion, stopping a toxic medication) and treats symptoms. Neuropathic pain is managed with medications such as certain antidepressants, anticonvulsants and topical agents, together with physical therapy, orthotic support and, when appropriate, interventional techniques. Autonomic complications may require specific measures for blood pressure, bladder care or sexual health. Prognosis depends on cause, extent of damage and whether the underlying condition can be controlled; some forms improve, others are chronic and progressive.

Notable distinctions

It is important to distinguish peripheral neuropathy from central nervous system disorders (spinal cord or brain disease) and from non-neurological causes of limb symptoms. Patterns of onset, distribution of deficits and testing results often direct clinicians to the correct diagnosis. For patient information and clinical guidelines consult further specialist sources: neuropathic pain information, sexual health guidance, and clinical reference sites linked through medical resources or foot care advice.