Regional Analyses of CNS Microdialysate Glucose and Lactate in Seizure Patients

Abstract

Summary:Purpose: To correlate glucose (and lactate) results obtained from microdialysate to recent studies suggesting that glucose transporter activity may be significantly altered in seizures.Methods: We used a fluorometric technique to quantify glucose and lactate levels in microdialysates collected from two to four depth electrodes implanted per patient in the temporal and frontal lobes of a series of four patients. Hour-by-hour and day-to-day changes in brain glucose and lactate levels at the same site were recorded. Additionally we compared regional variations in lactate/glucose ratios around the predicted epileptogenic region.Results: Lactate/glucose ratios in the range of 1-2:1 were the most commonly seen. When the lactate/glucose ratio was <1:1, we typically observed a relative increase in local glucose concentration (rather than decreased lactate), suggesting increased transport, perhaps without increased glycolysis. In some sites, lactate/glucose ratios of 3:1-15:1 were seen, suggesting that a circumscribed zone of inhibition of tricarboxylic acid cycle activity may have been locally induced. In these dialysates, collected from probes closer to the epileptogenic region, the large increase in lactate/glucose ratios was a result of both increased lactate and reduced glucose levels.Conclusions: We conclude that regional variations in brain extracellular glucose concentrations may be of greater magnitude than previously believed and become even more accentuated in partial seizure patients. Data from concomitant assays of microdialysate lactate and glucose may aid in understanding cerebral metabolism.

Persistent lactic acidosis in neonatal hypoxic-ischaemic encephalopathy correlates with EEG grade and electrographic seizure burden

“…Previous studies in adults have suggested that prolonged muscle contractions and muscle hypoxia are the source of lactate in prolonged seizures 20. During our continuous EEG monitoring we found that the majority of our seizures were electrographic only, with only brief clinical expression.…”

“…In animal studies a 10-fold rise in plasma lactate occurs between 3 and 10 minutes after seizure activity 18 19. Microdialysis of brain tissue has demonstrated increased lactate to glucose ratios during seizures in adult patients 20. Microdialysis, performed during the seizures in 1-day-old rats with hypoxic cerebral insults and prolonged seizures, demonstrated decreased glucose and adenosine triphosphate, with raised lactate and β-hydroxybutyrate 21.…”

Management of multifactorial idiopathic epilepsy in EL mice with caloric restriction and the ketogenic diet: role of glucose and ketone bodies

“…Glucose uptake and metabolism increases more during epileptic seizures than during most other brain activities [42-44]. Blood glucose also positively correlates with flurothyl-induced seizures in rats and high glucose may exacerbate human seizure disorders [45].…”

Neuro-inflammatory Sequelae of Minimal Trauma in the Non-traumatized Human Brain: A Microdialysis Study

“…The use of microdialysis, a minimally traumatic method, in patients without cerebral injury, was justified along with the use of deep intracranial electrodes, which was judged as necessary given the severity of their epilepsy and the expected benefit of the operative treatment. Microdialysis has already been used in suchlike cases in some studies in the past, mainly for the measurement of neurotransmitters (During et al 1993, Wilson et al 1996 and metabolic markers of ischemia (Cornford et al 2002, During et al 1994, and their correlation to seizure occurrence, while one study used the same methodology to correlate adenosine levels to the phases of sleep (Zeitzer et al 2006).…”