Peripheral Neuropathy
Peripheral neuropathy is damage to or dysfunction of the peripheral nerves — the motor, sensory, and autonomic fibres that connect the spinal cord to the rest of the body. It is one of the most common neurological problems, presenting with combinations of numbness, tingling, pain, and weakness that typically begin in the feet and spread proximally in the classic length-dependent pattern.
Definition
Peripheral neuropathy is a disorder of peripheral nerve function or structure that produces sensory, motor, or autonomic symptoms, most commonly as a symmetrical, length-dependent polyneuropathy with distal sensory loss and depressed reflexes.
Scope
This entry covers peripheral neuropathy as a clinical category: how nerve fibres are affected, the patterns that distinguish a length-dependent polyneuropathy from a focal mononeuropathy, the broad mechanistic divide between axonal and demyelinating processes, and the wide range of causes from metabolic to immune to hereditary. It is a reference description and not a guide to diagnosis or treatment.
Key concepts
- Length-dependent polyneuropathy
- Mononeuropathy and mononeuritis multiplex
- Axonal versus demyelinating neuropathy
- Sensory, motor, and autonomic fibre involvement
- Large-fibre versus small-fibre neuropathy
- Distal stocking-and-glove sensory loss
- Nerve conduction studies and electromyography
Mechanisms
Peripheral nerves can be injured in two broad ways: the axon itself can degenerate, or the myelin sheath can break down. Axonal neuropathies, the more common pattern, tend to begin distally in the longest nerves and produce the stocking-and-glove distribution, reflecting the vulnerability of long axons to metabolic and toxic insults. Demyelinating neuropathies slow or block conduction and can produce weakness out of proportion to wasting. The distribution of involved fibres — sensory, motor, autonomic, large or small — shapes the symptoms, and nerve conduction studies with electromyography are the standard tools for separating these mechanisms.
Clinical relevance
Because so many systemic conditions, most prominently diabetes, can injure peripheral nerves, neuropathy is a frequent reason for neurological assessment and a window onto underlying disease. This entry explains how neuropathies are conceptualised and classified for educational reference; it does not provide individualised diagnostic or therapeutic recommendations.
Epidemiology
Peripheral neuropathy is common, with prevalence rising sharply with age and reaching a substantial fraction of older adults; diabetes is among the leading causes worldwide, and diabetic neuropathy affects a large proportion of people with longstanding diabetes. Other major contributors include alcohol, nutritional deficiency, toxins, immune-mediated disease, and inherited disorders.
History
The systematic study of peripheral neuropathy advanced with the development of nerve conduction studies and electromyography in the twentieth century, which allowed clinicians to separate axonal from demyelinating disease and to localise focal nerve lesions. Reviews such as England and Asbury's synthesis consolidated a framework based on the tempo, distribution, and fibre types involved.
Related topics
Seminal works
- hughes-2002
- england-asbury-2004
- feldman-2019
Frequently asked questions
- Why does peripheral neuropathy usually start in the feet?
- Most common neuropathies are length-dependent, meaning the longest nerve fibres are affected first; because these reach the feet, numbness and tingling typically begin there and ascend over time in a stocking-and-glove pattern.
- What is the difference between an axonal and a demyelinating neuropathy?
- An axonal neuropathy reflects degeneration of the nerve fibre itself and tends to be length-dependent, whereas a demyelinating neuropathy reflects damage to the insulating myelin and slows or blocks conduction; nerve conduction studies are used to distinguish the two.