Abstracts

Rationale: Cortical spreading depression (CSD) is an acute pertubation of cerebral function related to migraine and acute brain injury in humans (Brain 2006;129:778-790). Animal studies demonstrate a complicated relation between CSD and seizure activity and suggest that CSD may cause secondary aggravation of brain injury. We tested the co-occurrence and interrelation of seizure activity and CSD in humans. Methods: 54 patients underwent craniotomy after head injury or spontaneous haemorrhage. Electrocorticographic (ECoG) recordings were taken near foci of damaged cortical tissue for up to 10 days, starting at 5 hours to 12 days post ictus. Results: One patient had seizure activity only, while 19 of the 54 patients only had CSDs. In 8 patients, CSD (5 to 34 episodes) and ECoGraphic seizures (1-81 episodes) co-occurred (p=0.02). Clinically overt seizures were only ob-served in one patient. Phenytoin treatment decreased the susceptibility to both seizure activity and CSD in one patient. In three patients CSD was immediately preceded by seizure activity that was subsequently terminated by the same CSD. In one patient each CSD was followed by a pause in repetitive seizure activity, and in another patient we observed that CSD did not invade a locus with ongoing seizure activity. In two patients the two phenomena co-occurred without obvious interaction. Conclusions: CSD and seizures interact in the acutely injured human brain in a complex fashion that reflect the various patterns observed in animal studies. CSD may increase the susceptibility of the cerebral cortex to seizures by suppressing synaptic inhibition, and seizure activity may trigger CSD. Conversely, CSD may terminate seizures. ECoG recordings may be a valuable tool in the assessment of cerebral cortical function and dysfunction in patients with acutely injured cerebral cortex. Non-invasive recording of CSD using surface EEG has not been possible so far, but our results indicate that if seizure activity is recorded in a patient with acute brain injury, it is likely that CSD epi-sodes occur too.