PAINFUL DIABETIC NEUROPATHY

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PAINFUL DIABETIC NEUROPATHY

Author: Rajesh Yadav

Diabetic Peripheral Neuropathies (DPN) are the most common type of neuropathies worldwide with up to 50% of people with type 2 diabetics eventually developing same degree of peripheral  neuropathy. There has been significant progress in understanding of the clinical aspects of these conditions, however many questions remains unanswered or difficult to answer in term of causation ,risk factors and genetic susceptibility ,effective treatments and restoration of nerve functions and pain management.

Diabetic polyneuropathy is one of the most common types of neuropathy. It is related to the duration of diabetes and glycemic control of diabetes. Unfortunately and despite numerous drug trials, other than strict glycemic control, which is often difficult to maintain, there are no other treatments to slow the progression or delay the development of DPN.

Pathophysiology:

Pathogenesis of painful symptoms remains unclear. In diabetic neuropathy a number of metabolic and vascular changes interconnect to cause damage to nerve cells with the primary underlying factor being hyperglycemic .Changes includes increased oxidative stress, a buildup of glycation and products, increased activity of the polyol pathway, activation of pro-inflammatory mechanism and ischemia .These process have direct and indirect effect on the neurons and blood vessels that supply the nerves.

Hyper excitability of and aberrant spontaneous impulse generation by damaged first order sensory neurons and their peripheral axons are well established processes that strongly contribute to pain associated with DPN.

Central neuropathic mechanisms can also contribute to pain experienced with diabetes. Severe studies have demonstrated that thalamic dysfunction occurs in patients with diabetes mellitus and that is experimental models of this disease, neurons in ventral posterior-lateral thalamus can become hyperexcitable, firing at abnormally high frequencies and generating aberrant spontaneous activity.

It affects all types of nerve fibers.

Diagnosis:

  1. History:

More than 80% of the patients with DM induced poly-neuropathy have distal, symmetric type of this condition. The initial symptoms are the signs of diminished sensation, burning feet, which may occurs particularly during night and worsen when touched and the sensation of tingling in feet. Attack of shooting pain also occurs.

Other examinations includes:

  • General inspection of Feet: For ulceration, callus, erythematous areas
  • Musculoskeletal assessment: For deformity Charcot neuro-osteoarthopathy(CNO)
  • Neurological assessment: Length dependent, non- dermatomal distribution of sensory loss(Gloves and stocking)
  • Vascular assessment: Heart rate and BP lying/sitting
  • Lab test:CBC,CRP,HbA1c,LFT,RFT,VitB12,folate,Thyroid function test,ECG,ECHO

Addition test:

  • Nerve conduction test(Gold standard)
  • EMG

Static Posturography test:

Eye may also be an important site of diagnosis and monitoring of neuropathy. Corneal nerve morphology is a promising marker of DPN occurring elsewhere in the body

Potential diagnostic role for retinal structure and visual functional marker in diagnostic and monitoring of DPNs.

Current technique:

  • Skin Biopsy
  • Nerve Biopsy

Management:

Intensive Glycemic Control

Medications:

  1. Anticonvulsants: Carbamazepine, Valproic acid, Gabapentin have been traditionally used.

Efficacy of Gabapentin has enhanced when combined with opoids such as morphine or sustained released oxycodine and highly effective when combined with nortriptylline.

2.Anti-Depressant:

3.Local Anesthetics:

  • Mexiletine –Oral
  • 5% Lidocaine patch

4.NMDA :Dextromethorphan

5.Opoids:Tramadol

Others:

  • Alpha –Lipoic acid
  • Topical Clonidine in foot pain

Combined Treatment:

Combination of pharmacotherapy can be used in instances where less than adequate response is obtained with monotherapy or when side effects limit further dose –up titration of single agent. A study demonstrates that combination of nortriptylline with Gabapentin at maximal tolerated dose was more effective than either of monotherapy.