Recirculation usually precedes malignant edema in middle cerebral artery infarcts

Objectives - In patients with large middle cerebral artery (MCA) infarcts, maximum brain swelling leading to cerebral herniation and death usually occurs 25 days after onset of stroke. The study aimed at exploring the pattern of compounds related to cerebral energy metabolism in infarcted brain tissue. Methods - Forty-four patients with malignant MCA infarcts were included after decision to perform decompressive hemicraniectomy (DHC). Cerebral energy metabolism was in all patients monitored bedside by 13 microdialysis catheters inserted into the infarcted hemisphere during DHC. In 29 of the patients, one microdialysis catheter was also placed in the non-infarcted hemisphere. MCA blood-flow velocity was monitored bilaterally by transcranial Doppler ultrasound. Results - The interstitial glucose levels were in both sides within normal limits throughout the monitoring period. Mean lactate/pyruvate (LP) ratio was very high in infarcted tissue immediately after DHC. The ratio slowly decreased but did not reach normal level during the study period. In the infarcted hemisphere, MCA blood-flow velocities increased from approximately 42 cm/s 1 day prior to DHC (nine of nine patients) to approximately 60 cm/s at day 4. Conclusions - Normal interstitial glucose level in the infarcted hemisphere in combination with substantial MCA blood-flow velocities bilaterally even before DHC was performed indicates that malignant brain swelling usually commences when the embolus/thrombosis has been largely resolved and recirculation of the infarcted area has started. The protracted increase of the LP ratio in infarcted tissue might indicate mitochondrial dysfunction.