Critical Care Medicine Georgetown University School of Medicine
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Introduction: Delayed cerebral ischemia (DCI) associated with vasospasm is a major contributor of morbidity and mortality following subarachnoid hemorrhage (SAH). Transcranial dopplers (TCD) monitor for vasospasm following a SAH however this has several limitations. Continuous electroencephalography (cEEG) with automated Alpha-Delta Ratio (ADR) monitoring has emerged as a potential tool for the early detection of cerebral ischemia.
Description: A 37-year-old woman presented with a sudden, severe left-sided headache followed by syncope. CT head revealed a large acute SAH and an aneurysm at the left A1/A2 junction. Neurologic examination was non-focal, though she exhibited nuchal rigidity. Nimodipine was initiated for vasospasm prevention and an external ventricular drain (EVD) was placed for ventriculomegaly and somnolence. Cerebral angiography followed by endovascular coiling was performed. The patient was monitored using cEEG with automated ADR trending starting on post-bleed day (PBD) 0. Although TCDs were planned to begin on PBD 4, cEEG trends on PBD 2 revealed a reduction in ADR suggestive of evolving cerebral ischemia. This prompted early TCD evaluation, revealing severe vasospasm despite an unchanged neurologic examination. MRI revealed a punctate infarct in the left caudate likely due to vasospasm. Norepinephrine infusion was initiated for blood pressure augmentation and cerebral perfusion optimization. Subsequently, TCDs showed improvement in velocities with no change in neurologic exam.
Discussion: This case illustrates the utility of ADR trends in identifying early vasospasm prior to TCD or neurologic decline. The ADR reflects cortical activity, and reductions correlate with cerebral ischemia. Several studies suggest that decreasing ADR may precede clinical symptoms and can serve as a marker for DCI. In this patient, the decrease in ADR on PBD 2 prompted earlier TCD screening and allowed for early recognition of vasospasm and prompt management which likely helped limit the extent of ischemia. While TCD remains a standard tool for vasospasm surveillance, it is limited to certain vascular territories and performed intermittently. cEEG in contrast, offers real-time monitoring and may be particularly useful in neurologically intact patients.
