Associate Professor Professor Dept. of Medicine JLN Hospital Ajmer Rajasthan Address for correspondence Dr Monika Maheshwari Naveen Niwas 434 10 Bapu Nagar Ajmer Rajasthan E mail opm11 rediffmail.com Abstract Diverse neurologic manifestations of hypoglycemia have been reported. Hypoglycemia can cause various neurologic symptoms including profound memory loss transient motor deficits a persistent vegetative state and death in 2 4 of cases. Brain magnetic resonance imaging MRI is a useful technique to evaluate hypoglycemic brain damage. We describe herein characteristic brain MR diffusion imaging features in a diabetic patient who had severe hypoglycemia. Keywords Diabetes post hypoglycemic brain injury MRI brain scan Diverse neurologic manifestations of hypoglycemia have been reported. These neurologic symptoms range from focal neurologic deficits to permanent dysfunction or death.1 3 The accumulation of excitatory amino acids and not simply glucose starvation of the neuron seems to play an important pathogenetic role.4 Brain magnetic resonance imaging MRI is a useful technique to evaluate hypoglycemic brain damage. We describe herein characteristic brain MR diffusion imaging features in a diabetic patient who had severe hypoglycemia. Case Report A 45 year old diabetic female was brought comatose in the casualty outdoor. On physical examination her pulse rate was 108 min blood pressure 100 70 mmHg and respiratory rate 26 min. Her extremities were cold clammy with profuse sweating. Jugular venous pressure JVP was normal. There was no pedal edema cyanosis icterus or lymphadenopathy. Lungs were clear. Neurological examination revealed power 3 5 in both upper and lower limbs with normal tone. Bilateral plantar reflex was extensor. Pupils were normal in size and reactive to light. Patient was then shifted for MRI brain scan which showed hyperintense areas of restricted diffusion involving the bilateral basal ganglia Fig. 1 characteristic of posthypoglycemic brain injury. Immediately blood glucose levels was then done which confirmed hypoglycemia blood sugar 40 mg . Patient was given 100 mL intravenous infusion of 25 dextrose stat. She regained consciousness. During her further hospital stay her insulin dose was resetted to optimal dose with proper instructions for dietary pattern and she was discharged on 10th day. Discussion Hypoglycemia can cause various neurologic symptoms including profound memory loss transient motor deficits a persistent vegetative state and death in 2 4 of cases.5 Some pathogenetic mechanisms for diffusion restriction picture in MRI brain have been proposed as follows Energy failure Excitotoxic edema Asymmetric cerebral blood flow. Glucose deprivation leads to arrest of protein synthesis in many regions incomplete energy failure and loss of ion homeostasis cellular calcium influx and intracellular alkalosis. Consequently neuroactive amino acid aspartate release into the extracellular space occurs and results in selective neuronal necrosis predominantly in the cerebral cortex caudoputamen and hippocampus.6 However protein synthesis in the cerebellum brainstem and hypothalamus remains unaffected because of the greater activity of the glucose transport mechanisms.7 Further in contrast to ischemic brain damage inability to produce lactic acid during hypoglycemia is thought to account for the fact that infarction is not seen in controlled experimental conditions producing a pure hypoglycemic insult to the brain. Thalamic lesions exist in ischemic encephalopathy but not in hypoglycemic coma. In hypoglycemia due to focal loss of autoregulation the frontal and parietal lobe areas have grossly decreased cerebral flow whereas the cerebellum and brainstem show almost no fall in local cerebral blood flow as seen in our patient also. There was a characterisitic band like area localized to right parietal lobe Fig. 1 . The predominant release of aspartate into the extracellular fluid in hypoglycemia differs from the rise in extracellular glutamate in ischemia.8 Second unlike ischemia energy failure is only moderate during hypoglycemia because of the remaining glucose supply and oxidation of endogenous nonglucose fuels by the brain.8 In contrast to cytotoxic edema excitotoxic edema does not imply neuronal damage because glutamate induces edema of glial cells and myelinic sheaths might protect axons from intracellular edema and irreversible damage. In addition glutamate reuptake systems are not impaired in hypoglycemia. 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