Definition and epidemiology
Peripheral neuropathy refers to dysfunction of one or more peripheral nerves, classified by the pattern of involvement:
- Mononeuropathy: single nerve (e.g., carpal tunnel syndrome)
- Mononeuritis multiplex: multiple, asymmetric individual nerves (seen in vasculitis)
- Polyneuropathy: diffuse, usually symmetric, length-dependent (most common pattern)
Distal symmetric sensorimotor polyneuropathy is the most frequent subtype encountered in practice and on exams.
Prevalence increases with age; diabetic peripheral neuropathy affects a substantial proportion of patients with long-standing diabetes (estimates commonly cited in the range of 30-50% after many years of disease). Globally, diabetes and leprosy are the most common causes, while in resource-rich settings diabetes, alcohol use, and chemotherapy-induced neuropathy predominate.
- Diabetes mellitus is the most common cause of peripheral neuropathy worldwide
- Classic pattern is distal, symmetric, length-dependent sensorimotor polyneuropathy
- Ankle reflex is lost early due to length-dependent axonal loss
- Mononeuritis multiplex (asymmetric, multiple nerves) suggests vasculitis
- Nerve conduction studies distinguish axonal from demyelinating neuropathy
- Vitamin B12 deficiency can cause combined peripheral neuropathy and spinal cord disease, unlike folate deficiency which spares the nervous system
- First-line pain agents are gabapentinoids, SNRIs, or tricyclic antidepressants
- Loss of protective sensation is the key driver of diabetic foot ulceration
Etiology and risk factors
Metabolic/endocrine
- Diabetes mellitus (most common cause overall)
- Chronic kidney disease (uremic neuropathy)
- Hypothyroidism
Nutritional/toxic
- Vitamin B12 or B1 (thiamine) deficiency; vitamin B6 deficiency or excess
- Alcohol use disorder
- Medications: chemotherapy agents (vincristine, cisplatin, paclitaxel), isoniazid, metronidazole, amiodarone, nitrofurantoin
- Heavy metal exposure (lead, arsenic)
Infectious
- Leprosy (leading infectious cause worldwide)
- HIV (direct effect or antiretroviral toxicity)
- Lyme disease
Autoimmune/inflammatory
- Guillain-Barre syndrome (acute)
- Chronic inflammatory demyelinating polyneuropathy (CIDP)
- Vasculitis (mononeuritis multiplex pattern)
Hereditary
- Charcot-Marie-Tooth disease
Other
- Paraneoplastic syndromes, monoclonal gammopathy/amyloidosis, idiopathic (a significant minority of cases remain unexplained despite workup)
Note: unlike vitamin B12 deficiency, folate deficiency does not cause peripheral neuropathy or other neurologic symptoms, a frequently tested distinction.
Pathophysiology
Nerve injury occurs through several overlapping mechanisms:
- Axonal degeneration: the axon dies back from its distal end, typically producing a length-dependent, symmetric pattern (classic in diabetes, toxic/metabolic causes). Longest nerves (to the feet) are affected first, explaining the stocking-glove distribution.
- Segmental demyelination: Schwann cells or myelin are damaged while the axon remains intact, producing patchy conduction slowing or block (classic in Guillain-Barre syndrome and CIDP).
- Vascular/ischemic injury: vasa nervorum occlusion in vasculitis causes infarction of individual nerves, producing the asymmetric mononeuritis multiplex pattern.
- Compression: focal mechanical injury at anatomically vulnerable sites (carpal tunnel, fibular head).
In diabetes, chronic hyperglycemia drives microvascular ischemia, accumulation of advanced glycation end products, and oxidative stress, damaging both axons and the vasa nervorum.
Clinical features
Symptoms depend on which fiber types are affected.
Sensory (usually first and most prominent)
- Numbness, tingling, burning pain, or "pins and needles" starting in the toes/feet
- Loss of vibration and proprioception (large fiber) or pain/temperature (small fiber)
- Allodynia (pain from normally non-painful stimuli) in painful neuropathies
Motor
- Distal weakness, foot drop, muscle atrophy, areflexia (ankle reflex lost first)
- Gait instability from loss of proprioception
Autonomic (when involved)
- Orthostatic hypotension, resting tachycardia
- Gastroparesis, erectile dysfunction, bladder dysfunction
- Anhidrosis or abnormal sweating
Pattern recognition
| Pattern | Suggests |
|---|---|
| Symmetric, distal, slow onset | Diabetes, toxic/metabolic, hereditary |
| Asymmetric, multiple nerves | Vasculitis (mononeuritis multiplex) |
| Acute, ascending, areflexia | Guillain-Barre syndrome |
| Chronic, relapsing, proximal + distal | CIDP |
| Single nerve territory | Entrapment/compression |
Diagnosis
Diagnosis is clinical, supported by targeted testing to identify the underlying cause.
History and exam
- Onset, tempo, distribution, and symmetry
- Monofilament testing and vibration sense (tuning fork) for diabetic screening
- Deep tendon reflexes (ankle jerk lost early)
Laboratory workup
- Fasting glucose/HbA1c
- Vitamin B12 level
- Thyroid function tests
- Renal function
- Serum protein electrophoresis if amyloidosis/monoclonal gammopathy suspected
- HIV testing, Lyme serology if clinically indicated
Electrodiagnostic studies
- Nerve conduction studies (NCS): distinguish axonal (reduced amplitude, preserved velocity) from demyelinating (reduced velocity, conduction block) patterns
- Electromyography (EMG): assesses denervation and reinnervation in motor fibers
Additional testing
- Skin biopsy for intraepidermal nerve fiber density (small fiber neuropathy, when NCS is normal)
- Nerve biopsy (reserved for suspected vasculitis or amyloidosis)
- Genetic testing if hereditary neuropathy suspected
Differential diagnosis
- Myelopathy or radiculopathy: can mimic distal numbness but typically show upper motor neuron signs or dermatomal pattern
- Multiple sclerosis: central lesions, often with other CNS signs
- Vitamin B12 deficiency (subacute combined degeneration): combined peripheral neuropathy and posterior column/corticospinal tract involvement
- Fibromyalgia: diffuse pain without objective sensory loss or abnormal NCS
- Peripheral vascular disease: claudication and vascular findings rather than sensory loss predominating
- Restless legs syndrome: nocturnal urge to move legs, normal nerve conduction studies
Management
Management addresses the underlying cause and symptomatic relief; approaches vary somewhat between guideline bodies but share common principles.
Treat the underlying cause
- Tight glycemic control in diabetes (slows progression, does not reverse established damage)
- Vitamin B12 replacement for deficiency states
- Discontinue or substitute offending drugs/toxins
- Immunotherapy (IVIG, plasmapheresis, or corticosteroids) for CIDP or Guillain-Barre syndrome
- Treat underlying infection (e.g., multidrug therapy for leprosy)
Neuropathic pain management (first-line agents, per American Academy of Neurology and European guidelines)
- Gabapentin or pregabalin
- Serotonin-norepinephrine reuptake inhibitors (duloxetine, venlafaxine)
- Tricyclic antidepressants (amitriptyline) as an alternative first-line option
Second-line/adjunct
- Topical agents (capsaicin, lidocaine patches) for localized pain
- Opioids and tramadol generally reserved for refractory cases given dependence risk
Supportive care
- Foot care education and regular inspection in diabetic patients to prevent ulceration
- Physical therapy, orthotics, and fall-prevention strategies
- Assistive devices for significant motor involvement
Complications and prognosis
- Foot ulceration and amputation: loss of protective sensation predisposes to unnoticed trauma and infection, especially in diabetes
- Falls and fractures: from impaired proprioception and gait instability
- Charcot joint (neuropathic arthropathy): joint destruction from repeated unrecognized trauma
- Autonomic complications: orthostatic hypotension, silent myocardial ischemia, gastroparesis
Prognosis depends on etiology: toxic/nutritional and compressive neuropathies may improve substantially after removing the cause, while diabetic and hereditary neuropathies are generally slowly progressive and only partially reversible. Guillain-Barre syndrome has a generally favorable prognosis with most patients regaining the ability to walk independently, though recovery can take months and a minority have residual deficits.
"DANG THERAPIST" for causes of peripheral neuropathy: Diabetes, Alcohol, Nutritional (B12), Guillain-Barre, Toxins/Trauma, Hereditary (CMT), Endocrine (hypothyroid), Renal failure, Amyloidosis, Paraneoplastic/Porphyria, Infection (leprosy, HIV, Lyme), Systemic (vasculitis), Tumor (compression).
Practice questions
1. A 58-year-old man with a 15-year history of type 2 diabetes mellitus reports gradually worsening numbness and burning pain in both feet over the past 2 years, now extending to his ankles. Examination shows reduced vibration sense and absent ankle reflexes bilaterally, with normal strength. Which of the following best describes the expected pathophysiologic pattern on nerve conduction studies?
2. A 45-year-old woman presents with progressive ascending weakness over 10 days, beginning in the legs and now involving the arms, with areflexia throughout. She reports a diarrheal illness 2 weeks ago. Cerebrospinal fluid analysis shows elevated protein with a normal white cell count. Which of the following is the most likely diagnosis?
3. A 62-year-old man with a history of monoclonal gammopathy presents with asymmetric weakness and numbness, first affecting the right foot and then, over subsequent weeks, the left wrist, in a pattern not following a single nerve root distribution. Skin examination reveals palpable purpura on the lower extremities. Which underlying process best explains this pattern of nerve involvement?
Frequently asked questions
What causes peripheral neuropathy?
The most common cause worldwide is diabetes mellitus, which damages nerves through chronic hyperglycemia and microvascular injury. Other important causes include alcohol use, vitamin B12 or B1 deficiency, certain chemotherapy drugs, kidney failure, autoimmune conditions like Guillain-Barre syndrome and CIDP, infections such as leprosy and HIV, and hereditary conditions like Charcot-Marie-Tooth disease. In a notable minority of cases, no cause is found despite thorough workup.
What are the first symptoms of peripheral neuropathy?
The earliest symptoms are usually tingling, numbness, or burning pain starting in the toes and feet, since the longest nerves are affected first. This often progresses slowly up the legs before involving the hands in a similar pattern. Loss of ankle reflexes and reduced vibration sense are early exam findings, sometimes before symptoms become bothersome.
How is peripheral neuropathy diagnosed?
Diagnosis starts with a detailed history and neurological exam checking reflexes, vibration sense, and pinprick sensation, followed by blood tests to identify treatable causes like diabetes, vitamin B12 deficiency, and thyroid disease. Nerve conduction studies and electromyography help confirm the diagnosis and distinguish axonal from demyelinating patterns. Additional tests like skin or nerve biopsy are reserved for specific suspected causes.
Is peripheral neuropathy curable?
It depends on the cause: neuropathy from a reversible trigger, such as vitamin deficiency, a toxic medication, or compression, often improves significantly once that cause is treated or removed. Diabetic and hereditary neuropathies are generally not curable and tend to progress slowly, though glycemic control can slow diabetic neuropathy. Treatment overall focuses on managing the underlying cause and controlling pain, since nerve damage already present is often only partially reversible.
Peripheral neuropathy vs radiculopathy — what is the difference?
Peripheral neuropathy involves damage to peripheral nerves themselves, typically causing symmetric, distal, length-dependent symptoms in a stocking-glove pattern. Radiculopathy results from compression or irritation of a nerve root, usually from a herniated disc, and causes pain, numbness, or weakness following a specific dermatomal or myotomal distribution, often with associated back pain. Imaging of the spine and the distribution of symptoms help distinguish the two.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: G64
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.