Figure 5.

Duration (in minutes) of recovery time of cortical electrical silence induced by depolarization in different diseases. The duration of the depression of cortical activity reflects the ability of the tissue to recover after cortical spreading depression (CSD) and thereby the perfusion and metabolic state at the point of measurement. The clinical deterioration of patients we have monitored is often accompanied by clusters of CSD, which show a gradual increase of recovery time. Therefore, assessment of recovery time may be an early warning sign that secondary damage is under development. So when is duration prolonged? In this figure, the mean duration of depression for all CSD episodes from 87 patients (intracerebral hemorrhage (ICH): 5, malignant hemispheric stroke (MHS): 13, subarachnoid hemorrhage (SAH): 43, traumatic brain injury (TBI): 26) is displayed in minutes. The figure suggests a bimodal distribution with a cluster below ∼8 minutes, probably reflecting a fast recovery and tolerable perfusion conditions, whereas the more widespread group above ∼8 minutes may reflect a reduced blood flow response indicating penumbral conditions. Interestingly, the small group of patients with ICH all showed a fast recovery, possibly because a widespread penumbra seems to be a rare feature in this condition.