Diabetic Neuropathy

Damage to the peripheral nervous tissue

Aetiology

Risk factors

• Increased length of diabetes

• Poor glycaemic control

• More common in T1DM

• High cholesterol/lipids

• Smoking

• Alcohol

• Genetics

• Mechanical injury

Peripheral neuropathy

• Pain/loss of feeling in feet, hands

• Distal symmetrical or sensorimotor neuropathy

• 'Glove and stocking' distribution

Symptoms

• Numbness/insensitivity

• Tingling/burning

• Sharp pains or cramps

• Sensitivity to touch

• Loss of balace and coordination

Complications

• Patient may continue to walk on a wounded foot - worsens injury and may lead to infection

• Complication of severe neuropathy that occurs in a well-perfused foot

1. Acute onset of a hot, swollen foot +/- pain

2. Bony destruction - if treatment is delayed, the foot can become deformed as bone is destroyed

3. Radiological consolidation and stabilisation - after 6-12 months

• MRI can differentiate between Charcot foot and infection

• Aim is to prevent/minimise bony destruction by keeping pressure off the foot - non-weight bearing, total contact cast or aircast boot

• Any resulting deformity can alter the pressure distribution across the foot and predisposes the foot to future ulceration

• Risk of amputation

• Interosseous wasting results in unbalanced traction by the long flexor muscles → high arch and clawing of toes

• Causes abnormal distribution of pressure on walking → callus formation

• Small bilateral pupils that do not constrict when exposed to bright light but do constrict when focused on a nearby object

• Highly specific sign of neurosyphilis but may also be a sign of diabetic neuropathy

Foot risk assessment

• Sensation unimpaired, foot pulses present

• Requires annual screening by health-care professional

• Sensation unimpaired, foot pulses present OR

• Inability to self-care for feet

• Requires annual assessment by podiatrist

• Sensation unimpaired, foot pulses present with skin callus or foot deformity OR

• Sensation impaired, foot pulses absent OR

• Previous foot ulcer/amputation

• Requires annual assessment by podiatrist

• Current foot ulcer, gangrene, critical ischamia, infection, or unexplained red, hot swollen foot

• Requires urgent referral to specialist team

Management of painful neuropathy

• Amitriptyline, duloxetine, gabapentin or pregabalin

• Topical capsaicin cream can be used for localised neuropathic pain in patients who do not want or can't tolerate oral treatments

Autonomic neuropathy

• Affects the nerves regulating heart rate and blood pressure as well as control of internal ogans such as those involved in GI motility, respiratory function, urination, sexual function and vision

• Usually in those with a long history of very poor diabetes control

• Can be intractable - recurrent admissions with vomiting or collapse

Digestive system

• Gastric slowing/frequency - constipation/diarrhoea (sometimes both)

• Gastroparesis (slow stomach emptying) - persistent N+V, bloating, loss of appetite
• Can make blood glucose levels fluctuate widely, due to abnormal food digestion

• Oesophagus nerve damage - may make swallowing difficult

• Improved glycaemic control

• Diet - smaller more frequent meals, low fat, low in fiber, if severe may need liquid meals

• Promotility dugs e.g. metoclopramide

• Anti-nausea medications e.g. prochlorperazine, and serotonin antagonists e.g. ondansetron

• Analgeisia: NSAIDs, low dose tricyclic antidepressants, gabapentin, tramadol and fentanyl for abdominal pain

• Severe cases: consider botulinum toxin, gastric pacemaker

Sweat glands

• Can affect the nerves that control sweating - prevents the sweat glands from working properly

• The body cannot regulate its temperature as it should

• Nerve damage can also cause profuse sweating at night or while eating - gustatory sweating

• Management: topical glycopyrolate, clonidine, botulium toxin

Heart and blood vessels

• BP may drop sharply after sitting or standing, causing a person to feel light-headed/faint (postural hypertension)

• Heart rate may stay high, instead of rising and falling in response to normal bodily functions and physical activity

• ECG: loss of R-R variability with respiration indicates patient has lost autonomic control of cardiac function

Proximal neuropathy

• Caused by damage to the nerves of the lumbosacral plexus

• Involves pain in the buttocks, hips, thighs or legs which is then followed by variable weakness in the proximal muscles of the lower limbs and then muscle wasting

• Rare, more commonly in elderly T2DM

• Often associated with weight loss

Focal neuropathy

• e.g. sudden weakness in one nerve or a group of nerves causing muscle weakness or pain e.g. carpal tunnel syndrome, cranial nerve palsy