Unexplained neurological deterioration after acute brain injury: A structured intensive care framework for targeted continuous electroencephalogram

Background: Neurological deterioration after acute brain injury is common in the intensive care unit, yet its cause may remain uncertain when repeat imaging is stable or does not fully explain the examination. Delayed recognition of occult structural, vascular, systemic, metabolic, medication-related, or electrographic mechanisms may postpone time-sensitive treatment. We aimed to provide a structured bedside framework and define the role of targeted continuous electroencephalography (cEEG). Methods: We performed a narrative synthesis of evidence and consensus recommendations across aneurysmal subarachnoid hemorrhage, intracerebral hemorrhage, ischemic stroke, traumatic brain injury, and acute subdural hematoma, emphasizing bedside examination, repeat neuroimaging, vascular reassessment, systemic physiology, medication effects, and critical care electroencephalogram (EEG). Results: Deterioration should first be confirmed as a true change and classified as explained, unexplained, disproportionate, or fluctuating/episodic. Evaluation should proceed in parallel: Correct reversible systemic and metabolic derangements, review sedative and analgesic exposure, and reassess structural or vascular complications. cEEG is most informative when deterioration remains unexplained after stabilization, exceeds the apparent imaging burden, fluctuates, follows a clinical seizure, or presents as delayed awakening. It can identify electrographic seizures, status epilepticus, and rhythmic or periodic patterns; however, a nonexplanatory recording neither establishes neurological stability nor excludes nonelectrographic secondary injury. Conclusion: A structured intensive care framework may reduce premature diagnostic closure and support timely, selective cEEG. Continuous EEG should complement, not replace, repeated clinical examination, neuroimaging, vascular evaluation, and correction of systemic physiology.