Diabetic Neuropathy
Commonest cause of peripheral neuropathy in the UK. Affects ~50% of diabetic patients. Distal symmetric polyneuropathy is the predominant form. Major risk factor for diabetic foot ulceration and amputation. Prevention through glycaemic control is key (DCCT/UKPDS trials).
Key Facts
Commonest cause of neuropathy in UK: affects ~50% of patients with diabetes; major contributor to diabetic foot disease Distal symmetric polyneuropathy (DSPN): most common form (~75%); length-dependent sensory > motor; glove-and-stocking distribution Painful diabetic neuropathy: affects ~25% of diabetic patients; burning, shooting, lancinating pain; worse at night Other forms: autonomic neuropathy, diabetic amyotrophy (proximal motor), mononeuropathies (CN III — pupil-sparing), mononeuritis multiplex Prevention: tight glycaemic control reduces neuropathy risk by ~60% in T1DM (DCCT) and significantly in T2DM (UKPDS) Pain management (NICE CG173): first-line amitriptyline, duloxetine, gabapentin, or pregabalin; duloxetine 60-120 mg OD has best evidence for painful diabetic neuropathy Annual foot screening: 10g monofilament + clinical exam; NICE NG19
Overview
Key Facts
Diabetic neuropathy is the commonest microvascular complication of diabetes. Prevention through glycaemic control and early detection through screening are the most important interventions.
Epidemiology
~50% of diabetic patients have some neuropathy; ~25% have painful neuropathy. Risk increases with duration and poor control. Both T1DM and T2DM affected.
Aetiology
Hyperglycaemia is the primary driver. Other risk factors: dyslipidaemia, hypertension, smoking, obesity.
Pathophysiology
Polyol pathway (sorbitol accumulation), AGEs, PKC activation, oxidative stress, microvascular disease (vasa nervorum) → axonal degeneration and segmental demyelination.
Clinical Presentation
DSPN
- Gradual onset; sensory > motor; glove-and-stocking
- Numbness, tingling, burning pain (worse at night)
- Absent ankle jerks, loss of monofilament sensation
- Risk of painless injuries → neuropathic ulceration
Autonomic Neuropathy
- CV: resting tachycardia, orthostatic hypotension, silent MI
- GI: gastroparesis, constipation, diarrhoea
- GU: erectile dysfunction, neurogenic bladder
Other Forms
- Diabetic amyotrophy: painful proximal thigh weakness; self-limiting 12-18 months
- CN III palsy: pupil-sparing (key distinction from compressive cause)
Red Flags
- Loss of protective sensation → high amputation risk
- Charcot foot (hot, swollen, painless joint destruction)
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| B12 deficiency | Macrocytosis, glossitis (check — metformin causes B12 deficiency) | B12 level |
| Alcohol-related neuropathy | Alcohol excess, nutritional deficiency | History, LFTs |
| CIDP | Proximal + distal weakness, demyelinating NCS | NCS, CSF |
| Hypothyroid neuropathy | Weight gain, fatigue | TFTs |
| Vasculitic neuropathy | Mononeuritis multiplex, systemic features | ESR, ANCA, biopsy |
Diagnosis / Investigation
Bedside
- 10g monofilament, vibration (128 Hz tuning fork), ankle reflexes
Bloods
- HbA1c, B12 (metformin-induced deficiency), TFTs, SPEP, U&Es
Neurophysiology
- NCS: axonal sensorimotor polyneuropathy (if diagnostic uncertainty)
Autonomic
- Lying/standing BP, heart rate variability, gastric emptying study
Management
Prevention
- Optimise glycaemic control: DCCT (~60% reduction T1DM), UKPDS (T2DM)
- Cardiovascular risk management
Pain Management (NICE CG173)
- First-line: amitriptyline 10-75 mg ON, duloxetine 60-120 mg OD, gabapentin 300-3600 mg/day, or pregabalin 150-600 mg/day
- Combination therapy if monotherapy inadequate
- Topical capsaicin 0.075% for localised pain
- Pain clinic referral for refractory cases
Autonomic
- Orthostatic hypotension: fludrocortisone, midodrine
- Gastroparesis: domperidone 10mg TDS (short-term), dietary modification
- Erectile dysfunction: PDE5 inhibitors
Foot Care (NICE NG19)
- Annual risk assessment, podiatry, patient education
Prognosis
DSPN is slowly progressive. Tight glycaemic control slows but does not reverse established neuropathy. Diabetic foot ulceration: lifetime risk ~25%; 5-year mortality after amputation ~50%. Autonomic neuropathy with cardiac involvement: 5-year mortality ~25-50%.
Other Relevant Information
Types of Diabetic Neuropathy
| Type | Features | Prognosis |
|---|---|---|
| DSPN | Symmetric, sensory > motor, length-dependent | Chronic, progressive |
| Painful neuropathy | Burning, nocturnal | May improve spontaneously |
| Autonomic | CV, GI, GU dysfunction | Increases mortality |
| Diabetic amyotrophy | Proximal, painful, thigh weakness | Self-limiting |
| CN III palsy | Pupil-sparing | Self-limiting |
Key Trials
| Trial | Finding |
|---|---|
| DCCT | Tight control in T1DM reduces neuropathy by ~60% |
| UKPDS | Tight control in T2DM reduces microvascular complications |