The purpose of the present study is to evaluate the role of peripheral afferent input for spontaneous pain in painful diabetic polyneuropathy

Both peripheral and central changes in the nervous system contribute to the development of painful diabetic neuropathy, but how these changes contribute to the pain generation remains yet to be fully understood.

The purpose of this study is to evaluate if a peripheral regional nerve block relieves spontaneous pain in painful diabetic polyneuropathy.

Inclusion Criteria:

• Aged 18 years or older.
• Probably diabetic neuropathy confirmed using the Toronto criteria in a "conservative manner", i.e. three out of three symptoms/signs of neuropathy must be present (sensory neuropathy symptoms, distal reduced sensibility, reduced ankle reflexes) 7.
• Definite or probable neuropathic pain for minimum the last 6 months
• Mean pain intensity at > 4 NRS the last week17.

Since we expect a large effect of the block it is not necessary to discontinue pain medication.

Exclusion Criteria:

• Other causes of pain in the same area or other pain that cannot be distinguished from the neuropathic pain.
• Unable to understand and speak Danish.
• Non-cooperative.
• Warfarin or other medication that contraindicate regional anesthesia.
• Infection in the injection area.
• Allergy to lidocaine.
• Pregnancy or lactating (fertile women must to show negative pregnancy test or use anticonception).
• Severe psychiatric disease e.g. severe depression during the last 6 months.
• Alcohol or drug abuse.