Diabetic neuropathy

Diabetic neuropathy comprises the peripheral and autonomic neurologic syndromes caused by diabetes mellitus and is one of the most common, disabling, and heterogeneous chronic complications of diabetes. It does not identify a single nerve lesion with a uniform course, but a clinical spectrum of conditions differing in anatomic distribution, fibers involved, rate of progression, pathogenic mechanism, and functional impact. By far the most common form is distal symmetric polyneuropathy, which primarily affects the longest sensory and motor fibers in a length-dependent pattern and initially manifests in the feet before ascending the legs and, at more advanced stages, involving the hands. Other forms include diabetic autonomic neuropathy, cranial and peripheral mononeuropathies, entrapment neuropathies, radiculopathies, lumbosacral radiculoplexus neuropathy, and other atypical or acute forms, including those that may occur after rapid correction of severe hyperglycemia.

Its clinical burden is enormous because diabetic neuropathy not only causes pain or sensory abnormalities, but profoundly changes foot biomechanics, increases the risk of ulceration and amputation, reduces balance and gait safety, alters autonomic cardiovascular function, may impair digestion, urination, sexual function, and sweating, and is associated with increased mortality. A substantial proportion of patients are also minimally symptomatic or completely asymptomatic early on despite already having lost protective sensation. Active screening is therefore essential, and diabetic neuropathy cannot be diagnosed only when a patient reports pain.

From an epidemiologic standpoint, diabetic neuropathy affects a large proportion of people with diabetes. Estimates vary according to definitions, diagnostic tools, and populations studied, but distal symmetric polyneuropathy affects approximately one-quarter or more of adults with diabetes in population studies and may involve up to about half of people with diabetes over a lifetime. Prevalence increases with disease duration, age, poor glycemic control, and other metabolic and cardiovascular factors. Cardiovascular autonomic neuropathy is also much more common than it appears in clinical practice, is often underdiagnosed early, and is associated with markedly worse prognosis.

The established etiologic cause of diabetic neuropathy is diabetes mellitus, meaning persistence of an abnormal metabolic environment capable of damaging nerve fibers, Schwann cells, the endoneurial microcirculation, and peripheral autonomic structures over time. The glucose value alone, however, does not fully explain the problem. Diabetic neuropathy arises from the interaction of chronic hyperglycemia, glycemic variability, insulin resistance, dyslipidemia, visceral obesity, oxidative stress, chronic low-grade inflammation, mitochondrial dysfunction, and microvascular insufficiency of the nerve. Risk therefore rises not only with elevated glycated hemoglobin and diabetes duration, but also with hypertension, smoking, hypertriglyceridemia, advanced age, chronic kidney disease, and poor control of the overall cardiometabolic profile.

Metabolic injury to peripheral nerves is sustained by multiple converging biochemical pathways. Hyperglycemia activates the polyol pathway, causing sorbitol and fructose accumulation within nerve cells, consuming NADPH, reducing antioxidant defenses, and promoting osmotic and oxidative injury. Formation of advanced glycation end products increases simultaneously; these alter structural and receptor proteins, stiffen the microcirculation, and activate proinflammatory signals. Protein kinase C and the hexosamine pathway are also activated, changing gene transcription and worsening endothelial function. The common biologic endpoint is excess mitochondrial oxidative stress, which damages axons and supporting cells and reduces the nerve’s ability to maintain ionic homeostasis and structural integrity.

Alongside purely metabolic injury, a fundamental microvascular component is present. The vasa nervorum, the small vessels supplying peripheral nerves, develop basement membrane thickening, endothelial dysfunction, reduced vasodilation, and impaired endoneurial perfusion. The result is chronic nerve ischemia, which compounds metabolic toxicity and amplifies its effects. In other words, the diabetic nerve exists in an environment in which less oxygen arrives while the nerve is also less able to use available energy efficiently. This combination promotes distal axonal degeneration, slowed conduction, and progressive loss of sensory, motor, and autonomic fibers.

The longest fibers are the most vulnerable, explaining the classic “stocking” distribution of distal symmetric polyneuropathy. The most distal axonal segments have the highest metabolic demands and depend most on efficient axonal transport; when diabetes impairs metabolism, microperfusion, and trophic support, these portions begin to degenerate first. Early involvement may primarily affect small A-delta and C fibers, responsible for nociception and thermal sensation, causing burning pain, stabbing sensations, allodynia, or dysesthesia even without striking findings on a traditional neurologic examination. Large myelinated fibers are subsequently or simultaneously affected, with loss of vibration, reduced reflexes, impaired proprioception, and postural instability.

The pathophysiology of diabetic neuropathic pain does not simply coincide with fiber destruction. A substantial component of pain arises from ectopic hyperactivity of injured neurons, altered ion channels, peripheral and central sensitization, and remodeling of spinal and supraspinal pain circuits. Two patients with a similar degree of fiber loss may therefore have very different phenotypes, one dominated by hypoesthesia and the other by severe pain. Neuropathic pain is not a sign of a “still viable nerve,” nor does its absence necessarily imply mild neuropathy. In many patients, loss of protective sensation without pain is actually the most dangerous presentation because it exposes them to repeated trauma, ulceration, and delayed diagnosis.

Autonomic forms arise from involvement of sympathetic and parasympathetic fibers. In cardiovascular autonomic neuropathy, vagal parasympathetic injury often appears first, with loss of normal heart-rate variability and subsequent relative predominance of sympathetic tone. Clinically, this produces resting tachycardia and a reduced ability to adapt heart rate to physiologic stress; at more advanced stages, orthostatic hypotension, exercise intolerance, and greater vulnerability to silent ischemia, arrhythmias, and sudden death develop. In the gastrointestinal tract, autonomic injury impairs motility and coordination, promoting gastroparesis, constipation, diarrhea, or alternating motility disorders. Genitourinary manifestations include erectile dysfunction, retrograde ejaculation, reduced bladder sensation, incomplete emptying, and recurrent urinary tract infections. Sudomotor involvement alters the distribution of sweating and contributes to dry skin, fissures, and foot vulnerability.

Focal and multifocal neuropathies have partly different mechanisms. Cranial mononeuropathies, especially of the third cranial nerve, and some acute peripheral mononeuropathies appear to result largely from focal microvascular ischemia of the nerve. Entrapment neuropathies are promoted both by mechanical compression within narrow anatomic channels and by the greater vulnerability of a nerve already metabolically impaired. Diabetic radiculoplexus neuropathy, often called diabetic amyotrophy, instead has features suggesting an ischemic microvasculitic process with focal inflammation of roots and plexuses, distinct from classic distal polyneuropathy and characterized by subacute onset, intense pain, and asymmetric proximal weakness.

A particular entity is treatment-induced neuropathy of diabetes, an acute painful form that may occur after rapid and marked improvement in glycemic control in patients with severe chronic hyperglycemia. This phenomenon does not contradict the value of glycemic control, which remains central to long-term neuropathy prevention, but it requires clinical awareness: in vulnerable individuals, overly abrupt metabolic improvement may trigger an intense painful neuropathic syndrome often associated with autonomic dysfunction. This also confirms that diabetic nerve pathophysiology is more complex than a simple linear relationship between blood glucose and injury.

The most common clinical manifestation of diabetic neuropathy is distal symmetric polyneuropathy, which emerges in the history as a progressive, generally bilateral disorder initially confined to the feet. Patients may report plantar burning, stabbing sensations, tingling, pins and needles, electric shocks, lancinating pain, or cramps, especially in the evening and at night. In other cases, numbness, a “dead foot” sensation, difficulty feeling contact with the ground, or the impression of wearing thick socks while barefoot predominates. When small fibers are primarily involved, pain may be disproportionate to objective findings. When large fibers predominate, patients more often report unsteadiness while walking, tripping, difficulty in the dark, and reduced awareness of toe and foot position.

The typical progression is length-dependent. Symptoms begin in the toes, extend over the dorsum and sole, ascend the legs, and only after reaching a certain level appear in the hands in the classic “stocking-glove” pattern. Pain may be continuous or intermittent and may worsen with contact from bed sheets, temperature changes, or prolonged standing. Not every patient has pain, however. A substantial proportion develop asymptomatic or minimally symptomatic neuropathy detectable only on neurologic examination or screening tests, but no less clinically relevant because silent loss of protective sensation exposes them to unnoticed trauma.

The neurologic examination in distal symmetric polyneuropathy follows a fairly typical sequence. Early on, pinprick and temperature sensation diminish in the toes, followed by vibratory sensation at the malleolus or great toe, then the Achilles reflexes, and finally proprioception. Muscle strength is often preserved for a long time, but as injury progresses, weakness of the small foot muscles, instability, reduced dorsiflexion, and altered plantar loading may develop. Over time, deformities such as hammer toes, bony prominences, calluses, and biomechanical imbalance appear, increasing ulceration risk especially when combined with unsuitable footwear or peripheral artery disease.

The painful component has a particularly substantial impact on quality of life. Patients with painful neuropathy often sleep poorly, reduce physical activity, experience worsening mood and treatment adherence, and develop a vicious cycle in which pain, sedentary behavior, poorer metabolic control, and psychological vulnerability reinforce one another. Painful diabetic neuropathy must be recognized not merely as a peripheral symptom but as a complex chronic condition involving sleep, body perception, depression risk, and social functioning.

Cardiovascular autonomic neuropathy has a more insidious course. Initially, patients report almost nothing, except perhaps lower exercise tolerance or a vague sense of “shortness of breath” during efforts previously well tolerated. Resting tachycardia, reduced heart-rate variability, dizziness or blurred vision on standing, easy fatigability, palpitations, and true orthostatic hypotension with presyncope or syncope may subsequently occur. In some patients, the condition is associated with silent myocardial ischemia or attenuated perception of hypoglycemic and cardiovascular symptoms, further increasing clinical risk.

Gastrointestinal manifestations include early satiety, postprandial bloating, nausea, delayed vomiting of undigested food, constipation, intermittent diarrhea, or alternation of these symptoms. When gastroparesis predominates, patients may have marked glycemic variability because nutrient absorption becomes unpredictable. Neuropathic diarrhea, often nocturnal or postprandial, may alternate with periods of constipation and substantially impair quality of life.

Genitourinary manifestations are also common and often underreported unless actively sought. In men, erectile dysfunction may be an early sign of autonomic neuropathy and may coexist with vascular injury. Retrograde ejaculation and reduced orgasm may occur. In women, reduced lubrication, dyspareunia, orgasmic difficulty, and reduced sexual response may develop. Neurogenic bladder manifests as reduced sensation of filling, hesitancy, a weak stream, incomplete emptying, high postvoid residual volume, overflow incontinence, and predisposition to recurrent urinary tract infections.

Focal and multifocal forms have a different presentation. Cranial mononeuropathies, especially of the third nerve, cause diplopia, ptosis, and orbital or periorbital pain, often with pupil sparing in typical ischemic presentations. Peripheral mononeuropathies may affect the median, ulnar, peroneal, femoral, or other individual nerves. Entrapment neuropathies, particularly carpal tunnel syndrome, are very common in patients with diabetes and sometimes represent the first overt neuropathy. Diabetic amyotrophy, or lumbosacral radiculoplexus neuropathy, instead presents with acute or subacute pain in the hip, thigh, or buttock followed by proximal weakness, atrophy, weight loss, and marked asymmetry. Motor disability may be more prominent than sensory disturbance in this form.

Diagnosis of diabetic neuropathy follows an orderly clinical pathway beginning with recognition of risk and culminating in definition of the neuropathic phenotype. No single laboratory test can confirm the diagnosis by itself. The clinician must first determine whether the condition is distal symmetric polyneuropathy, painful small-fiber neuropathy, autonomic neuropathy, a focal or multifocal form, or a nondiabetic neuropathy occurring in a patient with diabetes. This distinction is decisive because diabetes is common in the population, and its presence does not automatically justify attributing every neuropathy to diabetes itself.

Screening for distal symmetric polyneuropathy should be scheduled systematically. In type 1 diabetes, assessment should begin after 5 years of disease, whereas in type 2 diabetes it should begin at diagnosis and continue at least annually. Patients with symptoms, loss of protective sensation, previous ulceration, or foot deformities require more frequent assessment. Initial diagnosis is entirely clinical and combines the history, foot inspection, and a simple bedside neurologic examination.

According to widely accepted recommendations, assessment should include tests of small fibers, such as pinprick and thermal sensation, and tests of large fibers, such as Achilles reflexes, vibratory perception, and the 10-g monofilament. The monofilament should never be used alone to “diagnose” neuropathy in general because its principal purpose is to identify loss of protective sensation and ulceration risk. It should therefore always be combined with at least one other neurologic assessment modality. Foot inspection should seek calluses, fissures, maceration, fungal infection, deformities, bony prominences, nail abnormalities, unsuitable footwear, and signs of unnoticed trauma.

The Toronto Consensus provides widely accepted official definitions for distal symmetric polyneuropathy and remains the most important reference for clinical and research characterization.

According to the Toronto Consensus, diabetic distal symmetric polyneuropathy may be defined as follows

• Possible: presence of typical neuropathic symptoms or signs in a distal symmetric distribution
• Probable: a combination of neuropathic symptoms and signs, particularly distal symmetric symptoms associated with reduced distal sensation and/or reduced or absent Achilles reflexes
• Confirmed: neuropathic symptoms and/or signs associated with abnormalities on nerve conduction studies or validated measures of small-fiber injury
• Subclinical: absence of symptoms and signs, but presence of instrumental abnormalities consistent with neuropathy

When the clinical picture is typical and the patient has mild to moderate distal symmetric polyneuropathy, many sophisticated tests are often unnecessary for a clinical diagnosis. Nerve conduction studies and electromyography become highly useful, however, when the presentation is atypical, asymmetric, rapidly progressive, predominantly motor, proximal, or multifocal, or when nondiabetic neuropathy is suspected. In the classic form, they show reduced potential amplitudes and slowed conduction in a predominantly axonal pattern, sometimes with secondary demyelinating features. They are also particularly important for documenting entrapment neuropathies and radiculoplexus neuropathy.

The issue of small fibers deserves particular attention. A patient may have burning pain, allodynia, and thermal disturbances while conventional neurophysiologic testing remains minimally abnormal because nerve conduction studies primarily examine large myelinated fibers. In these cases, sudomotor autonomic tests, quantitative sensory testing, skin biopsy with quantification of intraepidermal nerve fiber density, or, in expert centers, corneal confocal microscopy may be useful. These tools are not required for every patient, but help when small-fiber neuropathy is suspected and the clinical picture is not fully explained by standard tests.

Diagnosis of cardiovascular autonomic neuropathy requires a specific approach. Suspicion arises with resting tachycardia, reduced exercise tolerance, blood pressure fluctuations, orthostatic presyncope or syncope, absence of normal nocturnal blood pressure dipping, and other autonomic manifestations. Initial assessment includes measurement of resting heart rate, supine and standing blood pressure, and clinical evaluation of the chronotropic response to exercise. Second-level assessment is based on Ewing cardiovascular reflex tests, which evaluate heart-rate variability during deep breathing, transition from supine to standing, and the Valsalva maneuver, together with the blood pressure response to standing and isometric handgrip. In the classic definition, orthostatic hypotension is a persistent fall in systolic blood pressure of at least 20 mmHg, or 30 mmHg in the presence of supine hypertension, or a fall in diastolic pressure of at least 10 mmHg after standing.

Diagnosis of gastrointestinal, genitourinary, and sudomotor manifestations is primarily clinical and functional. Gastroparesis requires exclusion of mechanical causes and documentation of delayed gastric emptying with appropriate methods. Neurogenic bladder assessment requires a targeted history, urine culture when needed, ultrasound with postvoid residual measurement, and possibly urodynamic testing. Erectile dysfunction must be interpreted within the complex context of neuropathy, vascular injury, hormonal status, and psychological factors. Distal hypohidrosis or anhidrosis, as well as compensatory proximal hyperhidrosis, can often be recognized from the history and skin examination.

The differential diagnosis is mandatory when the presentation is not fully consistent with typical diabetic neuropathy. Vitamin B12 deficiency, hypothyroidism, advanced kidney failure as the predominant uremic cause, alcohol misuse, toxic or drug-induced neuropathies, monoclonal gammopathies, amyloidosis, vasculitis, hereditary neuropathies, compressive radiculopathies, chronic inflammatory demyelinating polyneuropathy, and other causes of distal pain or neurologic deficits must be excluded. Nondiabetic neuropathy should be considered particularly when onset is rapid, asymmetry is marked, motor weakness predominates, proximal involvement is substantial, or systemic signs are not explained by diabetes.

Diagnosing diabetic neuropathy therefore does not simply mean stating that “a patient with diabetes has tingling.” It means determining whether the injury is truly attributable to diabetes, which compartment of the peripheral nervous system is involved, its severity, its biomechanical consequences, and the associated risk of complications. Only then does treatment become genuinely rational.

Treatment of diabetic neuropathy requires a clear distinction among prevention of nerve injury, treatment of neuropathic pain, management of autonomic forms, and correction of the factors that transform neuropathy into ulceration, falls, amputation, or cardiovascular instability. No therapy yet reliably regenerates a diabetic nerve that is already severely damaged. Prevention and early diagnosis therefore remain the true cornerstones of clinical strategy.

Glycemic control is the first pillar. In people with type 1 diabetes, intensive improvement of metabolic control has clearly been shown to reduce the onset and progression of neuropathy. In type 2 diabetes, the benefit of glycemic control alone is more modest and the condition is more strongly influenced by the entire cardiometabolic profile. In practice, this means that patients with diabetic neuropathy should be managed through a multifactorial approach: glycemic control, weight reduction, treatment of hypertension and dyslipidemia, smoking cessation, regular physical activity, correction of nutritional deficiencies, and careful medication review. Exercise in particular appears to have favorable effects on nerve function, balance, pain, and some measures of autonomic function, in addition to its well-known general metabolic benefits.

In patients with distal symmetric polyneuropathy, foot care is an integral part of neurologic treatment. Education on daily self-inspection, appropriate shoes, orthotic insoles when indicated, prompt treatment of calluses, skin hygiene, and podiatric follow-up are as fundamental as medications. Once protective sensation has been lost, any further delay in biomechanical prevention increases the risk of ulceration and infection.

For painful diabetic neuropathy, pharmacologic treatment should be guided by the most up-to-date neurologic guidelines. The realistic goal is almost never complete elimination of pain, but a clinically meaningful reduction accompanied by improved sleep, function, and quality of life. The principal drug classes with favorable evidence include gabapentinoids, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, and sodium-channel blockers. In clinical practice, the most commonly used agents are pregabalin, gabapentin, duloxetine, amitriptyline or nortriptyline, and, in selected settings, drugs such as carbamazepine, oxcarbazepine, or lacosamide. Choice depends on age, frailty, insomnia, depression, fall risk, cardiovascular comorbidities, kidney function, and individual tolerability.

Topical therapies may be very useful in patients with localized pain or polypharmacy. A high-concentration capsaicin patch and, in some settings, topical lidocaine formulations have a role especially when limiting the systemic burden of adverse effects is desirable. For partially responsive forms, low- or moderate-dose combination therapy is often more reasonable than escalating a single drug to poorly tolerated levels.

Opioids should not be used routinely to treat painful diabetic neuropathy. Modern guidelines discourage them because of an unfavorable benefit-risk ratio, considering sedation, dependence, constipation, falls, and poor long-term control of neuropathic pain. Drugs historically used for this purpose, such as tramadol or tapentadol, also require great caution and are not the standard solution to the problem.

When pain is severe, chronic, and refractory, management must broaden to include sleep, mood, fear of movement, depression, anxiety, and reduced physical activity. Diabetic neuropathic pain worsens when patients stop moving, sleep poorly, and lose confidence in the possibility of control. Effective treatment is therefore often biopsychosocial and functional, not merely pharmacologic.

Autonomic forms require treatment targeted to the affected system. In cardiovascular autonomic neuropathy, the first step is to correct risk factors and medications that worsen hypotension or tachycardia and to provide education regarding hydration, cautious increases in salt intake when appropriate, compression stockings, slow changes in position, and fall prevention. If orthostatic hypotension is symptomatic and persistent, vasopressor agents such as midodrine or, in some settings, droxidopa may be used; fludrocortisone may be considered in selected cases but cautiously because of the risks of fluid retention, heart failure, and hypokalemia. Resting tachycardia rarely requires specific treatment unless symptomatic, while prognostic attention should focus primarily on overall cardiovascular risk stratification.

In diabetic gastroparesis, treatment begins with small frequent meals, reduction of fat and insoluble fiber, correction of dehydration, and better coordination between insulin therapy and gastric emptying. Prokinetic agents, such as metoclopramide for limited periods and domperidone where available and appropriate, may reduce nausea and delayed emptying but require attention to neurologic or cardiac adverse effects. Glucagon-like peptide-1 receptor agonists, which slow gastric emptying, may worsen the condition and should be reassessed when symptoms are substantial. More complex cases may require specialist gastroenterology assessment and advanced nutritional strategies.

For neurogenic bladder, scheduled voiding, monitoring of postvoid residual volume, treatment of urinary tract infections, and, when needed, specific urologic approaches are useful. Erectile dysfunction often responds to phosphodiesterase type 5 inhibitors when not contraindicated; however, the associated vascular and cardiovascular component must always be recognized because erectile dysfunction in men with diabetes may be both a neuropathic symptom and a marker of systemic vascular disease.

Focal and multifocal forms have different prognoses and treatments. Ischemic cranial mononeuropathies often improve spontaneously over weeks or months with metabolic control and symptomatic support. Entrapment neuropathies may require splinting, physical therapy, or surgical decompression when severe. Diabetic radiculoplexus neuropathy requires correct diagnosis, exclusion of alternative causes, pain control, rehabilitation, and nutritional support; the course is often slow, with partial or substantial recovery over months, although initial disability may be considerable.

The prognosis of diabetic neuropathy is highly heterogeneous. Classic distal symmetric polyneuropathy tends to be chronic and slowly progressive; it rarely fully regresses once advanced, but may stabilize or slow if the metabolic substrate improves early and sustainably. Pain may improve without complete nerve regeneration, whereas loss of protective sensation and biomechanical deformities tend to persist. Cardiovascular autonomic forms carry more serious prognostic implications because they are associated with increased cardiovascular events and mortality. Focal ischemic forms, by contrast, often have a relatively better prognosis with partial or complete spontaneous recovery. In summary, diabetic neuropathy is not inevitably irreversible at every stage, but the potential for recovery depends crucially on early diagnosis and prompt multifactorial intervention.

The most important complication of distal symmetric polyneuropathy is loss of protective sensation. When patients cannot perceive pressure, friction, heat, or microtrauma, the foot is repeatedly exposed to unrecognized mechanical injury. When osteoarticular deformities, calluses, unsuitable shoes, and peripheral artery disease are added, ulceration risk increases markedly. A neuropathic ulcer is therefore not simply a wound on a diabetic foot, but the biomechanical outcome of a limb that has lost the ability to defend itself from everyday stress.

Ulceration may lead sequentially to soft-tissue infection, osteomyelitis, the need for prolonged offloading, repeated hospitalizations, and, in the most severe cases, amputation. Neuropathy is one of the most important prerequisites for diabetic foot disease and a major reason why diabetes remains a leading cause of nontraumatic amputation. Even when amputation is avoided, every ulcer has a substantial prognostic impact because it increases the risks of recurrence, loss of independence, and impaired quality of life.

Large-fiber and proprioceptive impairment causes postural instability and falls. Patients walk less safely in the dark, perceive joint position less accurately, correct body sway more slowly, and tend to reduce activity and walking speed. This leads not only to fractures and trauma, but also to sedentary behavior, sarcopenia, and further metabolic deterioration.

A specific and feared complication of the neuropathic foot is Charcot arthropathy, in which repeated trauma to an insensate foot, together with neurovascular and inflammatory abnormalities, produces progressive collapse of osteoarticular architecture. The foot becomes warm, swollen, deformed, and biomechanically unstable. If not recognized early, this condition progresses to severe deformity with an extreme risk of chronic plantar ulceration.

Complications of cardiovascular autonomic neuropathy are particularly important prognostically. Orthostatic hypotension predisposes to presyncope, syncope, falls, and head injury; reduced heart-rate variability and impaired autonomic regulation are associated with greater arrhythmic vulnerability and increased mortality. Attenuated perception of ischemia or other cardiovascular warning signs may also delay recognition of acute events.

Gastrointestinal complications include malnutrition, weight loss, dehydration, unpredictable glycemic fluctuations, and poorer treatment adherence secondary to gastroparesis or intestinal motility disorders. Genitourinary complications include recurrent urinary tract infections, chronic postvoid residual urine, incontinence, persistent sexual dysfunction, and a major psychorelational impact. Sudomotor abnormalities promote dry skin, fissures, and infectious vulnerability of the foot.

Chronic neuropathic pain is itself a major complication. It disrupts sleep, reduces physical activity, worsens anxiety and depression, increases reliance on sedating drugs, and may transform moderate neuropathy into a syndrome with major global impact. Pain should therefore not be regarded as a simple additional symptom, but as a true cause of disability.

Finally, advanced diabetic neuropathy often identifies a patient with a high burden of microvascular and cardiometabolic disease. In this sense, neuropathy is not only a complication of diabetes but a marker of systemic vulnerability. When it appears, patients frequently also have kidney disease, retinopathy, cardiovascular disease, or other manifestations of target-organ injury, explaining why its presence substantially changes overall prognosis.