Improvement of Sensibility in the Foot in Diabetic Patients Induced by EMLA-application to the Lower Leg

• MRI [ Time Frame: MRI-examination, before application, 90 min after application, 24 hours after application ] [ Designated as safety issue: No ]
• fMRI [ Time Frame: fMRI-examination, before application, 90 min after application, 24 hours after application ] [ Designated as safety issue: No ]

Sensory input from the foot as well as all other body parts results in activation of sensory cortex.

It is well known that the cortical body map is experienced-dependant and can rapidly change in response to changes in activity and sensory input from the periphery [10-12]. Increased activity and sensory input from the hand results in expansion of the cortical hand representation [13-15], while decreased sensory input, for instance by anaesthesia, amputation or nerve injury, results in shrinkage of the cortical hand representation [16-21]. Due to the constant ongoing "cortical competition" between body parts the adjacent cortical areas expand and take over the silent area, deprived of sensory input.

The investigators have recently described striking examples of such rapid cortical re-organisations induced by selective cutaneous anaesthesia of the forearm: application of EMLA cream to the volar aspect of the forearm results in improved sensory functions of the hand [18] linked to expansion of the hand representational area in sensory cortex . In analogy, EMLA application to the lower leg in healthy controls results in improved sensory functions in the sole of the foot linked to expansion of the foot representational area in sensory cortex.

To test the hypothesis that EMLA application to the lower leg of diabetic patients will result in improved sensory functions in the sole of the foot as well as expansion of the foot representation in sensory cortex. The investigators hypothesize that repeated applications of EMLA will result in a long lasting sensibility improvement.

• Drug: EMLA cream
  The study subjects are treated either by 50 g of a local anesthetic agent containing 2.5% Lidocaine and 2.5% Prilocaine (EMLA®, AstraZeneca - Södertälje, Sweden) or a placebo cream, applied to the lower leg. The cream is applied under occlusive bandage (plastic foam and a tube) for 1.5 hours circumferential to the lower leg 10-12 cm distally of the tibial tuberosity and the malleolus at ankle level. Administration of the treatment cream as well as removal after 1,5 hour and at sensory assessment after 1.5 hour and 24 hours, and interviewing the patient about subjective experience from the treatment are performed by an independent research nurse, not involved in the sensory assessment.
• Drug: EMLA cream
  50g applied according to description of intervention

• Experimental: EMLA cream
  Interventions:

  • Drug: EMLA cream
  • Drug: EMLA cream
• Placebo Comparator: Placebo cream
  A placebo cream identical in appearance and consistency to the experimental cream
  Intervention: Drug: EMLA cream

Inclusion Criteria:

• Adult patients (18-75 years) suffering from diabetes with subjective sensory impairment in the sole of the foot.

Exclusion Criteria:

• Patients with painful neuropathy or established ulcer formation in toes or sole of the foot, known hypersensitivity to local anaesthetics, major vascular reconstructions, communication problems due to severe language problems.
• Patients with pacemakers or magnetic implants or suffering from claustrophobia will not be subjected to fMRI-investigation.