The nervous system can be affected by diabetes mellitus, bothdirectly and indirectly. Examples of direct effects are when bloodglucose levels get very high or very low, both of which can causethe brain to not function normally. Examples of indirect causewould be atherosclerosis. Atherosclerosis is accelerated due todiabetes mellitus, and therefore the risk of stroke isincreased.

The brain’s only source of fuel under normal conditions is glucose,and it likes it in just the right amounts. It actually can toleratehigh glucose levels, much better than low. The blood sugar fourtimes normal, for example although not good to have, will notdamage the brain. a blood sugar level 1/4 of normal, however, canbe life-threatening, leading to seizures, coma or death. The bodyis very good at giving warning signs of low sugar with symptomssuch as sweating, palpitations, anxiety, nausea and tremor. Butthese are not always completely fail-safe. When glucose getsextremely high, such as over 600 (or is associated with ketosis)then lethargy, and even coma can occur. often there areprecipitating factors that set off these high glucose states suchas infection, trauma, stroke, myocardial infarction, pregnancy, ornot taking one’s insulin. Sometimes it is the initial presentationof diabetes mellitus.

The other direct effect of diabetes is neuropathy. Neuropathy iswhen the nerve endings furthest from the body; often starting inthe feet, do not function normally; producing symptoms such asnumbness, tingling, pain, burning, lack of feeling and imbalance.Diabetes is one of the most common causes of this condition.Although there are competing theories as to its cause, nerves workoptimally when glucose and insulin are at the correct levels. Highglucose levels, metabolites of glucose, or circulation impairmenton a microscopic level may be causes of neuropathy. whatever thecause of neuropathy, it has been shown that the better the glucoseis controlled, the less prominent and slower the progression of thesymptoms.

Diabetes mellitus can accelerate atherosclerosis as noted above.This can affect different sized arteries, and when a blockageoccurs, the part of the body “downstream” from that blockage getsan inadequate blood supply. in the heart, angina or a myocardialinfarction can occur; in the legs peripheral vascular diseaseresults; and in the brain, a stroke can occur. Symptoms of strokevary greatly depending on the area of the brain involved. Weaknessor numbness of one side of the body, slurred speech, sudden visualchanges, or sudden unsteadiness are common signs. if symptomsresolve within 24 hours this is called a TIA or transient ischemicattack. Sometimes this is called a mini stroke. By this term peoplecan be referring to either symptoms that resolve within 24 hours orsymptoms that persist longer than 24 hours, but are minor. Eitherway, a TIA can be a warning sign and should prompt investigationinto its cause and correct as much as possible the risk factors forstroke. these include smoking, hypertension and diabetes, all ofwhich are treatable.

Restless leg syndrome has been shown to occur more frequently intype II diabetes mellitus. This syndrome is an uncomfortablefeeling more often in the legs, but can involve the arms as well.It occurs when one is trying to rest or go to sleep. This feelingprompts people to stretch, wiggle or massage their legs or get upand walk. This can occur with or without neuropathy.

Avoiding, minimizing, and delaying complications of diabetesmellitus, neurologic and otherwise, is one of the main goals ofdiabetes control.

Questions or comments can be addressed to Stuart N. Kieran, MD,c/o Bitterroot Neurology, 1019 West Main Street, Hamilton, MT59840.