[Polyneuropathies - What are possible causes?]

Polyneuropathies are among the most common neurological diseases and the complaints they cause are a frequent reason for a consultation in general medical care. Around 5-8% of people over the age of 55 are affected, with an upward trend due to the ageing population, the increase in diabetes mellitus and many new neurotoxic drugs. As the name "poly" indicates, several peripheral nerves are affected. Depending on the cause, motor, sensory or even autonomic nerves can be affected individually or in combination. Sensory and motor symptoms occur (sensitive: numbness, prickling, tingling, unsteady gait and sharp, jabbing, throbbing or burning pain; motor: muscle cramps, muscle weakness, skeletal deformities). Clinically, polyneuropathies usually present insidiously with these symptoms and frequently with pain in the feet, often symmetrical and distally emphasized ("stocking pattern"). The disease can affect the insulating layer of the nerves (myelin) and/or the extension of the nerve cell (neurite, axon) itself. The etiology is diverse, ranging from metabolic to toxic to genetic causes. Early diagnosis is crucial in order to treat any underlying disease and, if possible, prevent progression and complications. This paper describes the causes of polyneuropathies and, in particular, a valuable diagnostic procedure for investigating the causes. It is emphasized that the physiological loss of nerve fibers in older patients can also be the cause of a (mild) polyneuropathy or, in the sense of a "double crash", can trigger a clinically manifest polyneuropathy together with another possible cause.