Polyneuropathy is a generalised disease of the peripheral nerves due to damage to the axon and/or the myelin sheath. Estimates on the prevalence in the general population range from 2% to 7%.
Polyneuropathies are frequent neurological manifestations of systemic illnesses. For example, approximately 50% of diabetic patients and patients with advanced HIV infection develop a neuropathy. Most neuropathies caused by toxins and metabolic factors are axonal. The aetiologies of demyelinating polyneuropathy (e.g., Guillain-Barre syndrome [GBS], chronic inflammatory demylelinating polyradiculoneuropathy, monoclonal gammopathies, certain hereditary neuropathies) are limited.
Polyneuropathy most commonly presents as symmetric numbness, paraesthesias, and dysaesthesias in the feet and distal lower extremities (distal symmetrical sensorimotor polyneuropathy). In severe cases, sensory symptoms and signs progress proximally to fit a stocking-glove distribution. Balance and gait may be impaired. Early motor signs include atrophy of the intrinsic foot muscles and ankle weakness. The autonomic nervous system may be involved, resulting in symptoms such as early satiety, diarrhoea or constipation, erectile dysfunction, sweating disturbances, and orthostatic lightheadedness. Other clinical phenotypes may be present, including purely sensory or purely motor symptoms and polyneuropathies with an acute presentation (e.g, GBS).
Small-fibre neuropathies do no affect the large fibres measured by nerve conduction studies, but do show changes in nerve fibre density on biopsy and abnormalities in quantitative sensory testing. Small-fibre neuropathies may present with painful pure sensory syndromes, and may be idiopathic, or secondary to a variety of systemic causes.
Asymmetric neuropathies or neuropathies presenting initially with upper extremity signs or symptoms should alert the practitioner to alternate neuropathy diagnoses, including entrapment neuropathies (focal neuropathies) or vasculitic neuropathies (multifocal neuropathies). The differential diagnosis of focal and multifocal neuropathies overlaps but is distinct from that of polyneuropathies.
Hyperreflexia or other upper motor neuron findings should prompt the examiner to consider lesions of the central nervous system. Multiple lumbosacral radiculopathies may also mimic a polyneuropathy presentation.
- Guillain-Barre syndrome
- Cauda equina syndrome
- Mononeuritis multiplex (vasculitic neuropathy)
- Chronic inflammatory demyelinating polyradiculoneuropathy
- Hepatitis C
- Sjögren's syndrome
- Systemic lupus erythematosus
- Monoclonal gammopathy
- Chronic renal failure
- Paraneoplastic polyneuropathy
- Thiamine deficiency
- Pyridoxine (vitamin B6) deficiency or toxicity
- Lyme disease
- Vitamin E deficiency
- Copper deficiency
- Charcot-Marie-Tooth neuropathy
- Acute intermittent porphyria
- Mitochondrial neuropathy
- Fabry's disease
- Refsum's disease
- Tangier's disease
- Critical illness polyneuropathy and myopathy
- Coeliac disease and gluten sensitivity
Department of Neurology
MHL declares that he has no competing interests.
Richard M Paddison Professor
Chair, Department of Neurology
Editor-in-Chief for Journal of the Neurological Sciences
Louisiana State University Health Sciences Center School of Medicine
JDE is the Editor-in-Chief for the Journal of the Neurological Sciences. JDE is on the speakers' bureau for Grifols and Takeda. JDE is an author of articles cited in this topic.
Dr John D England and Dr Maxwell H Levy would like to gratefully acknowledge Dr Jeffrey W. Ralph, the previous contributor to this topic.
JWR declares that he has no competing interests.
Neurology and Neurological Sciences
YS is an author of a reference cited in this topic.
Chief of Service
Neurosciences/Head and Neck Directorate
Imperial Healthcare Trust
Charing Cross Hospital
RS declares that he has no competing interests.
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