Mistaken Identity: Pseudo-Subarachnoid Hemorrhage After Opioid-Induced Cardiac Arrest

Introduction: Pseudo-subarachnoid hemorrhage (PSAH) is a radiographic mimic of subarachnoid hemorrhage (SAH), characterized by symmetrical hyperattenuation of the basal cisterns and subarachnoid spaces on computed tomography (CT). We present a case of PSAH in a patient who developed global anoxic encephalopathy following cardiac arrest.


Description: A 24-year-old man presented to an outside hospital after being found unresponsive, apneic, and pulseless. Return of spontaneous circulation was achieved after two cardiopulmonary arrests. Initial CT head interpretation raised concern for diffuse bilateral SAH involving the suprasellar cisterns, prompting transfer to our tertiary center for possible neurosurgical intervention. The patient arrived at our intensive care unit with a Glasgow Coma Scale score of 3T and absent brainstem reflexes. Upon review by in-house neurologists noting no aneurysm on CT angiography, CT findings were determined to be more consistent with PSAH, notable for blurring of grey-white matter differentiation and diffuse sulcal effacement, along with hyperdense skull base/sulcal subarachnoid spaces without intraventricular hyperdensities. A positive fentanyl screen raised suspicion for opioid-induced pulseless electrical activity arrest. Electroencephalography revealed complete isoelectric suppression. Desmopressin was given for central diabetes insipidus and targeted temperature management started. The patient soon exhibited stereotyped decorticate posturing and clonus. Apnea testing was highly suggestive of brain death. Cerebral scintigraphy confirmed absence of intracerebral perfusion, diagnostic of brain death.


Discussion: Approximately 3% of all CT findings initially suspected to be SAHs are actually PSAHs. In this vignette, clinical context—presumed opioid overdose with subsequent cardiac arrest—and the radiographic features detailed above, were incredibly important when discerning between PSAH and SAH. Prompt distinction between the two pathologies is crucial as clinical implications and prognoses vary vastly, with SAH being a surgical emergency with the potential for neurologic recovery while PSAH in the setting of anoxic brain injury invariably has a devastating outcome. Early recognition of PSAH can also save medical resources by avoiding transfers to tertiary care centers.