Identification of Decompressive Craniectomy Patients with Refractory ICP using Burst Suppression Ratio and Novel Subgaleal qEEG: A Technical Note.

Decompressive hemicraniectomy (DHC) can improve outcome in patients with elevated intracranial pressure (ICP) refractory to medical therapy. However, this transition point for treating refractory ICPs with DHC is unclear as ICPs can often be controlled with escalating doses of medical management. A more individualized and precise way to monitor and define medically ?refractory ICP? may be achieved with the utilization of a quantitative electroencephalography (EEG) parameter called burst suppression ratio (BSR). This technical note describes a novel device to continuously gather EEG data from subgaleal electrodes. We present two cases where BSR (i.e. an EEG-derived marker) was associated with maximal cortical suppression, indicating refractory ICP and indication for decompression. Two patients [severe traumatic brain injury (sTBI) and ruptured arteriovenous malformation (AVM)] had BSRs measured through placement of novel subgaleal EEG electrodes. Although both patients had ICPs controlled by a combination of sedation, hyperosmolar therapy, and hypothermia, the BSR over a 20-24 hour period quickly reached almost-complete EEG suppression (BSR > 90%). Each case had different reasons for delaying DHC, however both reached maximal medical therapy. Given the limit of ICP control was reached, DHC was conducted in both cases. Patient 1 failed to recover and was compassionately extubated. Patient 2 clinically recovered and was discharged to acute rehabilitation. These cases illustrate that utilization of a novel subgaleal EEG system to continuously monitor BSR in patients who are being medically managed for ICP control may be used to select appropriate candidates for surgical decompression. In our two cases, a threshold BSR value > 90% (induced by medical therapy) was associated with the indication for DHC. This can be used in the future as another tool to define the limit of cortical suppression by medical therapy, thereby, indicating decompression.