Background: The pathogenetic factors underlying development of diabetic polyneuropathy (DP) remain unclear. Reduced neurotrophic stimulation has been proposed as a possible mechanism. The neurotrophic factors IGF I and II, sCD-163, NGF, VEGF and BDNF are essential for development and regeneration of the nervous system. In earlier studies reduced concentrations of IGF-I and II in blood and reduced concentrations of NGF and BDNF in muscle and skin biopsies have been found in patients with DP. Purpose: Our purpose is to determine the concentration and biological activity of Insulin-like Growth Factor I and II (IGF-I and II), soluble Cluster of Differentiation 163 (sCD-163), Nerve Growth Factor (NGF), Vascular Endothelial Growth Factor (VEGF) and Brain-derived Neurotropic Factor (BDNF) in cerebrospinal fluid and in blood in patients with diabetes and/or nerve disease (especially diabetic polyneuropathy) as well as in healthy control subjects. We will furthermore relate the findings to peripheral nerve function. In addition the composition of the cerebrospinal fluid will be analyzed using mass spectrometry. Hypothesis: We hypothesize that DP develops due to reduced concentration and biological activity of neurotrophic factors. We expect the concentration of IGF-I and II, VEGF, NGF and BDNF to be reduced in cerebrospinal fluid in patients with DP compared to diabetic patients without damage to the nervous system and healthy control subjects. Methods: Study subjects consists of patients from Department of Neurology and Department of Department of Clinical Medicine (Endocrinology and Diabetes) Aarhus University Hospital, Denmark, who are having a lumbar puncture performed.