Box 39.1 Differential diagnosis of diabetic neuropathy

Uraemia

Vitamin B₁₂/folate deficiency

Hypothyroidism

Amyloidosis, acute intermittent porphyria

Toxins: alcohol, medications (e.g. chemotherapy), heavy metals (lead, mercury)

Inflammation: chronic inflammatory demyelinating polyneuropathy, connective tissue diseases/vasculitis

Infection: HIV, leprosy

Paraneoplastic syndromes

Hereditary sensory and motor neuropathy

Diagnostic evaluation of diabetic bladder dysfunction includes cystometry and urodynamic studies.

Treatment

Chronic painful diabetic neuropathy is difficult to treat. With tighter glycaemic control, clinically detectable neuropathy is reduced in both type 1 (DCCT findings) and type 2 diabetes. Although tighter glycaemic control improves nerve conduction velocity, existing symptoms may not improve. Hypoglycaemic unawareness due to autonomic neuropathy may limit efforts to optimize glycaemic control.

Pain control

Tricyclic antidepressants (e.g. amitriptyline) are useful in the treatment of painful neuropathy. However, their use may be limited by side-effects such as sedation. Nortriptyline and desipramine are associated with lower levels of sedation.

Duloxetine is also effective in reducing pain scores. Side-effects include somnolence and constipation. Other agents used for painful neuropathy include pregabalin, oxycodone, tramadol, gabapentin, carbamazepine, phenytoin, lamotrigine, venlafaxine and capsaicin cream. Difficult cases should be referred to pain management teams.

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