Peripheral Neuropathy — Symptoms, Causes & Treatment | MyMedicPlus

Peripheral neuropathy is a broad term encompassing diseases and dysfunction of the peripheral nervous system (PNS) — the network of nerves outside the brain and spinal cord comprising 43 pairs of spinal nerves, 12 cranial nerves, and the autonomic nervous system. The peripheral nervous system connects the central nervous system to limbs and organs, transmitting sensory information (touch, pain, temperature, proprioception) from the periphery centrally and motor commands from the brain and spinal cord to muscles peripherally. When peripheral nerves are damaged, impaired, or degenerating from any cause, the resulting clinical syndrome depends on which nerve fibre types are affected: sensory nerves produce abnormal sensations (paraesthesia, pain, numbness), motor nerves produce weakness and atrophy, and autonomic nerves produce cardiovascular, gastrointestinal, and urogenital dysfunction. Peripheral neuropathy has a population prevalence of approximately 2.4% — rising to 8% in adults over 55 years — and represents one of the most common neurological conditions encountered in clinical practice. Diabetic peripheral neuropathy (DPN) is the most prevalent form in high-income countries — affecting 50-70% of people with diabetes over their lifetime and accounting for the majority of non-traumatic lower limb amputations. Neuropathy is classified anatomically: mononeuropathy (one nerve — e.g., carpal tunnel syndrome — median nerve); mononeuritis multiplex (multiple individual nerves — e.g., vasculitic neuropathy); polyneuropathy (diffuse, symmetric, distal-predominant — e.g., diabetic, alcoholic, Charcot-Marie-Tooth); and radiculopathy (nerve root compression). Electrodiagnostically, neuropathies are classified as axonal (loss of the nerve axon — reduced amplitude, normal or mildly slowed conduction velocity) or demyelinating (damage to the myelin sheath — severely slowed conduction velocity, prolonged distal latency, conduction block).

Peripheral neuropathy has numerous causes, grouped by pathophysiological category. Metabolic causes: diabetes mellitus (the most common cause in high-income countries — 50-70% of diabetics develop DPN over their lifetime; caused by advanced glycation end-products [AGEs] damaging Schwann cells and endoneural blood vessels, oxidative stress, polyol pathway activation, and impaired axonal transport); chronic kidney disease (uraemic neuropathy — axonal, distal symmetric, improves with dialysis or transplantation); hypothyroidism (compression mononeuropathies and distal sensorimotor polyneuropathy — may be the presenting feature; reverses with thyroxine replacement); liver disease (alcoholic and hepatic neuropathy). Nutritional deficiencies: vitamin B12 deficiency (sub-acute combined degeneration of the cord and peripheral neuropathy — posterior and lateral column involvement, dorsal column sensory loss, myelopathy; caused by veganism, pernicious anaemia, metformin use [which reduces ileal B12 absorption], and gastric surgery); thiamine (B1) deficiency (Wernicke's encephalopathy and peripheral neuropathy — particularly in alcohol dependence and post-bariatric surgery); vitamin B6 (pyridoxine) toxicity causes sensory neuropathy paradoxically when supplemented above 100mg/day. Toxic causes: Chemotherapy-induced peripheral neuropathy (CIPN) — the most common treatment-limiting side effect of anticancer therapy; vincristine (severe predominantly motor/autonomic), taxanes (paclitaxel, docetaxel — sensory, painful, dose-dependent), oxaliplatin (acute cold-triggered sensory symptoms plus chronic length-dependent sensory neuropathy), cisplatin (sensory, irreversible in 30%), bortezomib (painful sensory neuropathy, improves after dose reduction); alcohol excess (chronic axonal sensorimotor polyneuropathy — combined direct toxicity and B-vitamin deficiency); heavy metals (arsenic, lead, thallium — acute severe neuropathy); organic solvents. Infectious: HIV neuropathy (distal sensory polyneuropathy, affects 30-50% of HIV patients even on ART; also DILS — diffuse infiltrative lymphocytosis syndrome); Lyme disease (Borrelia burgdorferi — Lyme radiculoneuropathy, mononeuritis multiplex); leprosy (Mycobacterium leprae — the most common cause of infectious neuropathy globally; pure neuritic form causes asymmetric sensorimotor neuropathy with thickened nerve trunks); herpes zoster and post-herpetic neuropathy; CMV neuropathy in immunocompromised. Inflammatory and autoimmune: Guillain-Barré syndrome (GBS — acute inflammatory demyelinating polyneuropathy, AIDP — most common pattern; post-infectious, molecular mimicry from Campylobacter jejuni, EBV, CMV, COVID-19; ascending weakness, areflexia, cytoalbuminous dissociation in CSF); chronic inflammatory demyelinating polyneuropathy (CIDP — acquired demyelinating, usually proximal and distal, relapsing); multifocal motor neuropathy (MMN — conduction block, anti-GM1 antibodies); vasculitic neuropathy (polyarteritis nodosa, ANCA-associated vasculitis — mononeuritis multiplex from nerve ischaemia). Hereditary: Charcot-Marie-Tooth disease (CMT — the most common hereditary neuropathy, prevalence 1:2500; CMT1A from PMP22 duplication — slowly progressive distal weakness and sensory loss, high arched feet, hammer toes, no ankle jerks; CMT2A from MFN2 mutations — axonal variant).

Symptoms depend critically on which nerve fibre types are damaged. Sensory symptoms are most common in length-dependent polyneuropathies (starting distally in feet and toes, progressing proximally in a 'stocking-and-glove' distribution). Positive sensory symptoms (from ectopic nerve discharge): paraesthesia (tingling, pins and needles — constant or episodic); allodynia (normally non-painful stimuli — light touch, clothing contact, bedsheets — perceived as painful); hyperalgesia (exaggerated pain response to normally painful stimuli); burning or electric shock-like dysaesthesias — particularly prominent in diabetic and chemotherapy-induced neuropathy; lancinating (shooting, stabbing) pains; and cold allodynia (oxaliplatin neuropathy). Negative sensory symptoms (from nerve fibre loss): numbness; impaired vibration sense (tuning fork test — 128Hz at the first metatarsal head is a sensitive screening tool for DPN); reduced joint position sense (proprioception) causing sensory ataxia (wide-based gait, positive Romberg's sign — patient sways or falls when standing with feet together and eyes closed); temperature sensation loss (risk of unnoticed burns and frostbite); reduced pain sensation (risk of neuropathic foot ulceration). Motor symptoms: distal muscle weakness (foot drop from tibialis anterior weakness — causing foot slapping and steppage gait; hand weakness for fine motor tasks); muscle wasting (interosseous wasting in CMT — 'hollow hand appearance'); fasciculations (visible muscle twitching); and absent ankle reflexes (near-universal in significant polyneuropathy and CMT). Autonomic symptoms (prominent in diabetic autonomic neuropathy, amyloid neuropathy, GBS): orthostatic (postural) hypotension — dizziness and syncope on standing from loss of sympathetic vasoconstrictor tone; gastroparesis — early satiety, nausea, vomiting, unpredictable glycaemia from gastric emptying delay; erectile dysfunction and retrograde ejaculation; urinary retention or incontinence; anhidrosis (inability to sweat) causing heat intolerance; cardiac autonomic neuropathy — resting tachycardia, loss of heart rate variability, silent myocardial ischaemia, and sudden cardiac death (leading cause of death in cardiac autonomic neuropathy from diabetes). Acute emergency presentation: GBS — ascending flaccid paralysis starting in the legs, progressing to involve arms, intercostal muscles (respiratory compromise requiring ventilatory support in 25-30%), and cranial nerves (facial diplegia, dysphagia); combined with areflexia and back pain or radicular pain.

Peripheral neuropathy diagnosis integrates clinical assessment, electrodiagnostic studies, laboratory investigations, and occasionally nerve or skin biopsy. Clinical assessment: detailed history of symptom onset (acute onset within days — GBS, toxic; subacute weeks-months — CIDP, B12, toxic; chronic insidious — DPN, hereditary CMT); distribution (symmetric vs asymmetric, distal vs proximal, limb vs cranial); neurological examination: sensory testing with monofilaments (10g Semmes-Weinstein for protective sensation threshold in DPN), tuning fork (128Hz vibration at first metatarsal head — impaired in 50-70% of DPN), pin-prick, and cold; strength testing (Medical Research Council scale); reflex testing (absent ankle jerks are a consistent early sign of polyneuropathy). Nerve conduction studies (NCS) and electromyography (EMG): the gold standard electrodiagnostic investigation — NCS measures nerve conduction velocity (NCV), amplitude, and distal latency; distinguishes axonal (reduced amplitude, normal NCV) from demyelinating (severely slowed NCV below 70% of LLN, prolonged distal latencies, prolonged F-waves, conduction block) neuropathy; EMG detects active denervation (fibrillations, positive sharp waves) and chronic reinnervation changes in axonal neuropathy. Blood tests for aetiology: HbA1c (diabetes); serum B12 (must also measure methylmalonic acid and homocysteine if borderline — more sensitive); thyroid function (TSH, free T4); full blood count (macrocytic anaemia in B12 deficiency); renal function (urea, creatinine, eGFR); liver function; serum protein electrophoresis (SPEP) — M-band paraprotein (IgM, IgG, IgA) indicates paraproteinaemic neuropathy; ANA, ANCA, anti-Ro/La, RF — vasculitic and connective tissue disease screen; hepatitis B and C serology; HIV test; anti-ganglioside antibodies (anti-GM1 for MMN; anti-GQ1b for Miller Fisher syndrome; anti-GD1b for sensory GBS); Borrelia serology (Lyme disease); and VDRL (syphilis — neurosyphilis increasingly encountered). Cerebrospinal fluid (CSF) examination: in GBS — cytoalbuminous dissociation (elevated protein above 1g/L with normal white cell count below 10/mm³); in CIDP — elevated protein. Nerve biopsy (sural nerve biopsy): reserved for cases where diagnosis remains uncertain after clinical and electrodiagnostic assessment — demonstrates onion-bulb formations (chronic demyelinating neuropathy), vasculitic changes, amyloid deposits, or inflammatory infiltrates. Skin punch biopsy (intraepidermal nerve fibre density — IENFD): the gold standard test for small-fibre neuropathy (SFN) — the small unmyelinated C-fibres and thinly myelinated A-delta fibres are not detected by standard NCS; IENFD below the 5th percentile for age and sex confirms SFN (presents with burning feet, autonomic symptoms, and normal NCS). Genetic testing: PMP22 duplication/deletion (CMT1A) by MLPA; MFN2, MPZ, GJB1 for other hereditary neuropathies.

Treatment of peripheral neuropathy comprises two parallel goals: treating the underlying cause (aetiology-specific — the most impactful intervention when available) and managing neuropathic pain symptoms. Cause-specific treatments: diabetes — intensive glycaemic control reduces DPN incidence and progression (DCCT trial: 64% reduction in diabetic neuropathy with intensive insulin therapy); also risk factor control (blood pressure, cholesterol); vitamin B12 replacement (oral cyanocobalamin 1mg daily or IM hydroxocobalamin 1mg every 3 months for severe deficiency or malabsorption); thyroid hormone replacement for hypothyroid neuropathy; alcohol abstinence (prevents further axonal injury — recovery is slow but significant); GBS — IVIG (2g/kg over 5 days — first-line, equivalent to plasma exchange [PE], both superior to steroids; start within 2-4 weeks of symptom onset); CIDP — IVIG (initial and maintenance), corticosteroids (prednisolone), subcutaneous immunoglobulin (SCIG, Hizentra); vasculitic neuropathy — prednisolone plus cyclophosphamide; paraproteinaemic neuropathy — haematology referral for underlying plasma cell disorder assessment and treatment; CIDP with IgM paraprotein — rituximab; chemotherapy reduction or discontinuation for CIPN when clinically feasible. Neuropathic pain pharmacotherapy (NICE CG173, first line for any painful peripheral neuropathy — except post-herpetic neuralgia): duloxetine (30-60mg daily — serotonin-noradrenaline reuptake inhibitor, NICE first-line for diabetic peripheral neuropathy; NNT approximately 5); pregabalin (150-600mg/day — alpha-2 delta calcium channel modulator; NNT 4-5 for DPN and post-herpetic neuralgia; licensed Schedule 5 CD in the UK); gabapentin (1200-3600mg/day — similar mechanism to pregabalin, generic and cheap; comparable efficacy; NICE first-line option for neuropathic pain); amitriptyline (25-75mg nocte — tricyclic antidepressant, inhibits reuptake of serotonin and noradrenaline; NNT 3 for pain relief; limited by anticholinergic side effects — constipation, dry mouth, sedation, and contraindication in cardiac arrhythmia). Second-line and adjunctive: capsaicin 8% patch (Qutenza — 30-60 minutes applied by healthcare professionals; depletes substance P from TRPV1-containing nociceptive fibres; for localised painful peripheral neuropathy when systemic medications are ineffective or poorly tolerated); tramadol (weak opioid with noradrenergic activity — second-line for moderate-severe neuropathic pain); lidocaine patches for localised neuropathy; alpha-lipoic acid 600mg IV or oral (ALADIN and SYDNEY trials — antioxidant, improves symptoms and objective measures in DPN). Physical therapies: physiotherapy for weakness, balance impairment, and gait retraining; orthotic devices (ankle-foot orthosis/AFO for foot drop); occupational therapy for fine motor loss. Pain clinic referral for refractory neuropathic pain — multimodal management including psychological pain coping strategies, TENS (transcutaneous electrical nerve stimulation), spinal cord stimulation.

Diabetic foot disease and lower limb amputations: DPN-associated loss of protective sensation enables unnoticed trauma, pressure sores, and thermal injury to progress to neuropathic foot ulceration — affecting 2-4% of diabetic patients per year; DPN combined with peripheral arterial disease creates a particularly severe scenario causing deep tissue necrosis and Charcot neuroarthropathy; diabetic foot ulcers cause approximately 70% of non-traumatic lower limb amputations in high-income countries, with the UK alone performing over 7,000 major amputations annually from this cause. Charcot neuroarthropathy (Charcot foot): an acute and chronic destructive arthropathy of the foot and ankle occurring in diabetics with severe sensorimotor and autonomic neuropathy — abnormal bone remodelling causes progressive joint destruction, fractures, and deformity without pain sensation; requires urgent diagnosis (acute Charcot — hot, swollen foot in a diabetic with neuropathy) and immobilisation (total contact casting for 3-6 months) to prevent irreversible foot deformity and subsequent ulceration risk. GBS complications: 25-30% of GBS patients require mechanical ventilation from respiratory muscle paralysis; 3-5% mortality from complications (ARDS, nosocomial infection, cardiac arrhythmia from autonomic instability, VTE from immobility); 20-30% have residual significant disability (weakness, fatigue) at 1 year; pain affects 50-75% of GBS patients during the acute and recovery phase. Chronic neuropathic pain is a profoundly disabling complication of any peripheral neuropathy — causing sleep disruption (in 50-60%), depression (35-40%), anxiety, reduced mobility, social withdrawal, and severely impaired quality of life; treatment-refractory neuropathic pain is one of the most challenging and undertreated clinical problems in neurology. Falls and fractures: proprioceptive loss and weakness from neuropathy substantially increases falls risk — hip fracture is a major cause of morbidity and mortality in patients with established peripheral neuropathy. Cardiac autonomic neuropathy (CAN) in diabetes causes resting tachycardia, exercise intolerance, and silent myocardial ischaemia — patients with CAN have a 3-5 times higher cardiovascular mortality and 5-year mortality of 25-50%.

Prevention of diabetic peripheral neuropathy — the most prevalent form — is the highest-impact preventive goal in peripheral neuropathy management. Intensive glycaemic control from the time of diabetes diagnosis is the most effective intervention: the DCCT trial demonstrated that intensive insulin therapy in Type 1 diabetes reduces the risk of clinical DPN by 64% and the risk of progression by 57% over 6.5 years; similar benefits have been demonstrated in Type 2 diabetes (ADVANCE, ACCORD trials). Metformin monitoring for B12 deficiency: patients on long-term metformin should have annual serum B12 monitoring and supplementation started when levels are subnormal or borderline — metformin reduces ileal B12 absorption through an unknown mechanism and B12 deficiency neuropathy mimics DPN. Diabetic foot care and education: annual comprehensive foot examination (monofilament, vibration, pulse assessment) in all diabetic patients; patient education on foot inspection, footwear, and avoiding trauma; referral to a specialist multidisciplinary diabetic foot clinic for high-risk feet (neuropathy plus any ulceration, deformity, or PAD). Alcohol use disorder treatment: structured alcohol cessation intervention reduces progressive axonal damage; thiamine (B1) supplementation (prophylactic Pabrinex or oral thiamine 100-300mg/day) in all alcohol-dependent patients to prevent Wernicke's encephalopathy and alcoholic neuropathy. CIPN prevention: dose modification or scheduling changes for neurotoxic chemotherapy; cryotherapy (cooling gloves and socks during taxane infusions) reduces CIPN incidence by 30-50% in early trials; duloxetine has the best evidence for treating established CIPN (ASCO guidelines). Hereditary neuropathy (CMT): physical therapy, orthotic supports (AFOs), and regular physiotherapy from childhood slow functional decline and prevent contractures; genetic counselling for affected families. Occupational exposure prevention: regular neurological monitoring for workers exposed to neurotoxic heavy metals and solvents; chelation therapy for established heavy metal neuropathy. Lyme disease prevention: tick bite prevention (DEET repellent, tick checks, appropriate clothing in endemic areas), early antibiotic treatment of Lyme disease prevents neurological manifestations.

Call emergency services (999/112) immediately for: rapidly ascending leg weakness from the feet upwards — particularly with difficulty walking, back pain, and absent reflexes (possible Guillain-Barré syndrome — can progress to respiratory failure in 25-30% requiring ventilation; urgent nerve conduction studies and IVIG initiation are needed within the first 2-4 weeks); shortness of breath developing in a patient with GBS or acute neuropathy (diaphragm and intercostal muscle paralysis is a medical emergency requiring ICU admission); sudden loss of bladder and bowel control with leg weakness and saddle anaesthesia (cauda equina syndrome — spinal surgical emergency, not peripheral neuropathy). See a neurologist urgently for: acute onset severe sensory loss, weakness, or pain spreading rapidly (within days to weeks — GBS, vasculitic neuropathy, toxic neuropathy requiring urgent diagnosis and treatment); a hot, painlessly swollen foot in a diabetic patient (acute Charcot neuroarthropathy — immediate total contact casting is required to prevent permanent foot deformity; delayed diagnosis causes irreversible bone destruction). See your GP for: burning, tingling, or numbness in the feet lasting more than a few weeks — particularly in a known diabetic (DPN assessment) or in anyone with unexplained symptoms (screen for B12, diabetes, thyroid, kidney disease); worsening balance or falls (proprioceptive loss from neuropathy is a common, treatable, and underappreciated cause of falls in the elderly); neuropathic foot pain unresponsive to paracetamol or codeine (duloxetine, pregabalin, or gabapentin are specifically effective for neuropathic pain and should be prescribed, not escalating non-opioid analgesics).