polyneuropathies

Polyneuropathy refers to dysfunction of multiple peripheral nerves. It is usually symmetric and begins in the distal limbs, with sensory symptoms often preceding weakness. Involvement can affect motor, sensory, and autonomic fibers.

Classification includes patterns (length-dependent stocking-glove versus non-length dependent), time course (acute to chronic), and pathology (axonal versus demyelinating). Clinically it may be sensory, motor, or autonomic, or a combination.

Common causes include diabetes and prediabetes; metabolic disorders; nutritional deficiencies (notably vitamin B12); alcohol use; toxins (chemotherapy agents, arsenic, lead); autoimmune disorders (CIDP, Guillain-Barré syndrome); infections (HIV, hepatitis C); inherited neuropathies such as Charcot‑Marie‑Tooth; uremia; thyroid disease.

Typical presentation is distal symmetric sensory disturbance (tingling, numbness, burning) with reduced vibration and proprioception, leading to imbalance. Later, distal weakness may appear. Autonomic symptoms can include orthostatic hypotension, GI motility issues, and bladder dysfunction.

Diagnosis relies on history and exam; nerve conduction studies and EMG differentiate axonal from demyelinating patterns. Laboratory testing targets possible causes (glucose tolerance, vitamin levels, autoimmune markers, infections). Skin biopsy may help diagnose small-fiber neuropathy. Imaging is used to assess non-nerve causes and to guide management.

Management focuses on treating the underlying cause when possible (glycemic control in diabetes, nutritional supplementation, removal of toxins, immunotherapy for immune-mediated forms). Symptom relief uses neuropathic-pain agents (gabapentinoids, SNRIs, tricyclics), topical agents, and physical therapy. Foot care and rehabilitation reduce disability and improve quality of life.

Prognosis varies; some neuropathies stabilize or improve, while others progress and cause chronic pain, falls, ulcers, or functional impairment.