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 etiologies of demyelinating polyneuropathy (e.g., Guillain-Barre syndrome [GBS], chronic inflammatory demyelinating polyradiculoneuropathy, monoclonal gammopathies, certain hereditary neuropathies) are limited.
Polyneuropathy most commonly presents as symmetric numbness, paresthesias, and dysesthesias 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, diarrhea 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-fiber neuropathies do not affect the large nerve fibers measured by nerve conduction studies, but do show changes in nerve fiber density on skin biopsy and abnormalities on quantitative sensory testing. Small-fiber 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.
- Diabetes mellitus
- Vitamin B12 deficiency
- Toxin/drug induced
- Idiopathic polyneuropathy
- Guillain-Barre syndrome
- Cauda equina syndrome
- Mononeuritis multiplex (vasculitic neuropathy)
- Chronic inflammatory demyelinating polyradiculoneuropathy
- Hepatitis C
- Sjögren 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 disease
- Refsum disease
- Tangier disease
- Critical illness polyneuropathy and myopathy
- Celiac disease and gluten sensitivity
Use of this content is subject to our disclaimer