Diabetes mellitus and the nervous system

Diabetes mellitus is a disorder in which the concentration of blood glucose is persistently raised above the normal range. It occurs either because of a lack of insulin or because of the presence of factors which oppose the action of insulin. Hyperglycaemia results from insufficient insulin action. There are many associated metabolic abnormalities—notably, the development of hyperketonaemia when there is a severe lack of insulin, together with alterations of fatty acids, lipids, and protein turnover. Diabetes is a permanent condition in all but a few special situations in which it can be transient. A wide variety of disturbances affecting the central and peripheral nervous systems, either directly or indirectly, may be encountered in patients with diabetes mellitus. This short selective review concentrates on recent progress in the delineation of the clinical features of the neurological syndromes related to diabetes and their management. It will deal, sequentially, with the classification of diabetes, a listing of some genetic disorders that may be accompanied by diabetes, the consequences of acute metabolic decompensation, and somatic and autonomic neuropathies, cerebrovascular disease, certain infections that have a particular association with diabetes and, finally, congenital malformations. The division of diabetes into two major types has long been known. The current classification1 (table 1) distinguishes type 1 (otherwise known as insulin dependent diabetes mellitus, IDDM) and type 2 (non-insulin dependent diabetes mellitus, NIDDM). This classification is important because the two types are distinct both in causation and management and is thus of direct clinical relevance. View this table: Table 1 Aetiological classification of diabetes mellitus In Western Europe, type 1 diabetes accounts for perhaps 10%-20% of all patients, although in the world at large there seems to be an extraordinary increase in type 2 diabetes from an estimated 124 million at present to a predicted 221 million by the year 2010 with …