Painful diabetic neuropathy

Diabetes mellitus is one of the most common chronic medical conditions

• up to 60% may develop diabetic polyneuropathy
• the incidence is linked to the duration of diabetes
• among diabetic neuropathic patients within the UK, between 43% and 53% experienced painful symptoms to the lower limb (1)

Pathophysiology (1,2,3,4):

• pathogenesis of painful symptoms remains unclear
• previous studies have not demonstrated structural or functional differences in nerve fibres between painful and painless diabetic neuropathy
  • one study did demonstrate higher plasma norepinephrine levels in patients with painful compared with painless neuropathy
• the DCCT trial showed a reduced incidence of diabetic neuropathy in the intensive glycaemic control treatment group (3)
  • diabetic patients with painful neuropathy seem to have increased blood glucose flux and perhaps poorer glycaemic control compared with those with painless neuropathy (4)
• paradoxically an insulin neuritis has been noted to occur following rapid improvement in glycaemic control (5)
  • some have related this complication to endoneurial ischaemia, perhaps due to insulin-induced neural neovascularization and arterio-venous shunting (4)

Clinical features

• symptoms of painful diabetic neuropathy include burning pains, pins and needles, shooting pains down the legs, increased touch sensation (hyperaesthesia), and even numbness

Diagnosis (2):

• measurement of clinical pain is difficult because it can be influenced by the individual personality, past experiences and other psychological variables. Therefore pain assessment has to rely on subjective evaluation

Reference:

1. Spruce, M et al. The pathogenesis and management of painful diabetic neuropathy: a review. Diabetic Medicine 2003;20 (2): 88-98
2. Benbow, S. J. et al. Painful diabetic neuropathy. Diabetic Medicine 1999;16 (8): 632-644.
3. The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. New Engl. J. Med. 1993; 32(14): 977-86.
4. Kihara M, Zollman PJ, Smithson IL, Lagerlund TD, Low PA. Hypoxic effect of exogenous insulin on normal and diabetic peripheral nerve. Am J Physiol 1994; 226: E980–985
5. Oyibo, S et al.The relationship between blood glucose excursions and painful diabetic peripheral neuropathy: a pilot study. Diabetic Medicine 2002;19 (10): 870-873.