Pseudo-Subarachnoid Hemorrhage: A Potential Imaging Pitfall

AC, da Cruz Jr. LCH. The role of neuroimaging in the determination of brain death

Brain death is the irreversible cessation of all brain function. Although protocols for its determination vary among countries, the concept of brain death is widely accepted, despite ethical and religious issues. The pathophysiology of brain death is related to hypoxia and ischemia in the setting of extensive brain injury. It is also related to the effects of brain edema, which increases intracranial pressure, leading to cerebral circulatory arrest. Although the diagnosis of brain death is based on clinical parameters, the use of neuroimaging to demonstrate diffuse brain injury as the cause of coma prior to definitive clinical examination is a prerequisite. Brain computed tomography (CT) and magnetic resonance imaging (MRI) demonstrate diffuse edema, as well as ventricular and sulcal effacement, together with brain herniation. Angiography (by CT or MRI) demonstrates the absence of intracranial arterial and venous flow. In some countries, electroencephalography, cerebral digital subtraction angiography, transcranial Doppler ultrasound, or scintigraphy/single-photon emission CT are currently used for the definitive diagnosis of brain death. Although the definition of brain death relies on clinical features, radiologists could play an important role in the early recognition of global hypoxic-ischemic injury and the absence of cerebral vascular perfusion.

Pseudosubarachnoid hemorrhage: A systematic review of causes, diagnostic modalities, and outcomes in patients who present with pseudosubarachnoid hemorrhage

Background:

Patients with computed tomography (CT) findings consistent with subarachnoid hemorrhage without evidence of hemorrhage following autopsy or cerebrospinal fluid testing are termed to have pseudosubarachnoid hemorrhage (pSAH).

Methods:

A systematic review of literature was conducted based on the preferred reporting items for systematic reviews and meta-analysis statement. Studies were evaluated for associated cause of pSAH, imaging modality used in assessment, method of confirmatory testing, and clinical outcome.

Results:

Fifty studies were included in qualitative analysis including 197 cases of pSAH. Systematic review revealed 23 studies including 110 patients with pSAH attributed to hypoxic-ischemic brain injury following cardiac arrest. Three studies were included in meta-analysis that quantitatively analyzed differences in CT densities in patients with pSAH and true subarachnoid hemorrhage (true SAH). A random effects model meta-analysis showed a statistically significant decrease in densities in the Sylvian fissure in patients with pSAH compared to true SAH and a statistically significant decrease in densities in adjacent parenchyma in patients with pSAH compared to true SAH. Systematic review further revealed 32 patients with pSAH associated with spontaneous intracranial hypotension, 11 patients with pSAH related to infectious etiologies, 15 patients with pSAH associated with subdural hemorrhage, 20 cases of pSAH related to hyperhemoglobinemia, 2 cases related to valproate toxicity, and individual cases related to hyponatremia, diabetic ketoacidosis, sudden infant death syndrome, cerebellar infarction, and dialysis disequilibrium syndrome.

Conclusion:

This study is the first systematic review of causes, diagnostic modalities, and outcomes in patients who present with pSAH. A diagnosis of pSAH may be considered following assessment of CT densities following cardiac arrest.

Extended Pseudo-Subarachnoid Hemorrhage Post-Percutaneous Coronary Intervention

We report the case of an extended pseudo-subarachnoid hemorrhage (PSAH) related to contrast intracerebral diffusion from blood-brain barrier breakdown on periprocedural percutaneous coronary intervention right corticofrontal ischemic stroke. PSAH is a rare and complex phenomenon, and it is important to differentiate PSAH from subarachnoid hemorrhage to avoid inappropriate treatment with potentially severe consequences. (Level of Difficulty: Beginner.)

Pseudo-subarachnoid hemorrhage and gadolinium encephalopathy following lumbar epidural steroid injection

Patients with imaging findings concerning for subarachnoid hemorrhage, however, with no evidence of hemorrhage following autopsy or cerebrospinal fluid testing are diagnosed with having pseudo-subarachnoid hemorrhage. A 73-year-old female presented to the emergency department with altered mental status one day after undergoing a lumbar epidural steroid injection at an outside hospital; a noncontrast computed tomography scan of the head revealed evidence of diffuse hyperdensity within the subarachnoid space concerning for subarachnoid hemorrhage. The patient underwent magnetic resonance imaging which demonstrated diffuse opacification of the cerebrospinal fluid spaces with gadolinium and the diagnoses of pseudo-subarachnoid hemorrhage and gadolinium encephalopathy were made. The combination of the neurologic symptoms related to gadolinium encephalopathy and the radiographic findings of pseudo-subarachnoid hemorrhage can create a clinical presentation nearly identical to ruptured aneurysmal subarachnoid hemorrhage. Patient history, magnetic resonance imaging findings, and temporal changes in computed tomography provide vital tools in establishing a diagnosis of pseudo-subarachnoid hemorrhage, especially after an iatrogenic intrathecal contrast administration.

Pseudo-Subarachnoid Hemorrhage; Chronic Subdural Hematoma with an Unruptured Aneurysm Mistaken for Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) usually occurs due to aneurysmal rupture of intracranial arteries and its typical computed tomography (CT) findings are increased attenuation of cisterns and subarachnoid spaces. However, several CT findings mimicking SAH are feasible in diverse conditions. They are so-called as pseudo-SAH, and this report is a case of pseudo-SAH which is misdiagnosed as aneurysm rupture accompanied by bilateral chronic subdural hematoma (cSDH). A 42-year-old male with severe headache visited our institute. Non-contrast brain CT images showed increased attenuation on basal cistern, and cSDH on both fronto-temporo-parietal convexity with midline shifting. Trans-femoral cerebral angiography was done and we confirmed small aneurysm at right M1 portion of middle cerebral artery. Under diagnosis of SAH, we planned an operation in order to clip aneurysmal neck and remove cSDH. cSDH was removed as planned, however, there was no SAH and we also couldn't find the rupture point of aneurysm. Serial follow-up CT showed mild cumulative cSDH recurrence, but the patient was tolerant and had no neurologic deficit during hospitalization. We have checked the patient via out-patient department for 6 months, there are no significant changes in volume and density of cSDH and the patient also have no neurologic complications.

Development of pseudo-subarachnoid hemorrhage secondary to hypoxic-ischemic injury due to bleeding pulmonary arterio-venous malformation

Background

The computed tomography (CT) finding of a pseudo-subarachnoid hemorrhage (SAH) may lead the treating physician into a diagnostic dilemma. We present a case of a pseudo-SAH in a patient with post-resuscitative encephalopathy, secondary to a newly diagnosed bleeding pulmonary arterio-venous malformation (AVM).

Case presentation

A 19-year-old female presented acutely with massive hemoptysis. Cardiopulmonary resuscitation (CPR) followed, and the patient was subsequently intubated for airway protection with intensive care unit (ICU) admission. Urgent CT angiography of the thorax showed a bleeding pulmonary AVM, with evidence of hemothorax. Non-contrasted cranial CT initially revealed cerebral edema. Day 3 post admission, repeat cranial CT showed worsening cerebral edema, with evidence of pseudo-SAH. Patient passed away the next day.

Conclusions

Pseudo-SAH, if present, carries a poor prognosis. It should be recognized as a potential CT finding in patients with severe cerebral edema, due to various causes. The diagnosis is vital, to avoid wrongful treatment institution, as well as determination of cause of death.

Subarachnoid Mirage: A Case of Pseudosubarachnoid Hemorrhage

A 22-year-old man with a history of intravenous methamphetamine use presented with severe headache for 5 days, was afebrile, and had nuchal rigidity. Computed tomography and magnetic resonance imaging results were interpreted as revealing acute subarachnoid hemorrhage. Twenty-four hours later, he developed acute neurologic deterioration. A lumbar puncture was performed, revealing the presence of Staphylococcus aureus. The false-positive image mimicking blood was potentially a result of an extremely high protein concentration present in the cerebrospinal fluid, provoked by an intense inflammatory reaction leading to disruption of the blood-brain barrier. Pyogenic meningitis is one of the causes of pseudosubarachnoid hemorrhage, or a false diagnosis of subarachnoid hemorrhage, when one does not actually exist.

Nonaneurysmal "Pseudo-Subarachnoid Hemorrhage" Computed Tomography Patterns: Challenges in an Acute Decision-Making Heuristics

BACKGROUND

Acute aneurysmal subarachnoid hemorrhage (SAH) is a medical and neurosurgical emergency from ruptured brain aneurysm. Aneurysmal SAH is identified on brain computed tomography (CT) as increased density of basal cisterns and subarachnoid spaces from acute blood products. Aneurysmal SAH-like pattern on CT appears as an optical illusion effect of hypodense brain parenchyma and/or hyperdense surrounding cerebral cisterns and blood vessels termed as "pseudo-subarachnoid hemorrhage" (pseudo-SAH).

METHODS

We reviewed clinical, laboratory, and radiographic data of all SAH diagnoses between January 2013 and January 2018, and found subsets of nonaneurysmal SAH, originally suspected to be aneurysmal in origin. We performed a National Library of Medicine search methodology using terms "subarachnoid hemorrhage," "pseudo," and "non-aneurysmal subarachnoid hemorrhage" singly and in combination to understand the sensitivity, specificity, and precision of pseudo-SAH.

RESULTS

Over 5 years, 230 SAH cases were referred to our tertiary academic center and only 7 (3%) met the definition of pseudo-SAH. Searching the National Library of Medicine using subarachnoid hemorrhage yielded 27,402 results. When subarachnoid hemorrhage and pseudo were combined, this yielded 70 results and sensitivity was 50% (n = 35). Similarly, search precision was relatively low (26%) as only 18 results fit the clinical description similar to the 7 cases discussed in our series.

CONCLUSIONS

Aneurysmal SAH pattern on CT is distinct from nonaneurysmal and pseudo-SAH patterns. The origin of pseudo-SAH terminology appears mostly tied to comatose cardiac arrest patients with diffuse dark brain Hounsfield units and cerebral edema, and is a potential imaging pitfall in acute medical decision-making.

Anoxic Brain Injury Presenting as Pseudosubarachnoid Hemorrhage in the Medical Intensive Care Unit

Anoxic encephalopathy is frequently encountered in the medical intensive care unit (ICU). Cerebral edema as a result of anoxic brain injury can result in increased attenuation in the basal cisterns and subarachnoid spaces on computerized tomography (CT) scans of the head. These findings can mimic those seen in acute subarachnoid hemorrhage (SAH) and are referred to as pseudosubarachnoid hemorrhage (pseudo-SAH). Pseudo-SAH is a diagnosis critical care physicians should be aware of as they treat and evaluate their patients with presumed SAH, which is a medical emergency. This lack of awareness could have important clinical implications on outcomes and impact management decisions if patients with anoxic brain injury are inappropriately treated for SAH. We describe three patients who presented to the hospital with anoxic brain injury. Subsequent CT head suggested SAH, which was subsequently proven to be pseudo-SAH.

The pseudo-SAH sign: an imaging pitfall in postmortem computed tomography

Postmortem computed tomography (PMCT) of the brain has an important role in detection of subarachnoid hemorrhage (SAH), which has a high mortality rate. However, a phenomenon known as "pseudo-SAH," or high-attenuation areas along the cisterns mimicking SAH, may be seen on CT. The aim of this study was to evaluate the diagnostic accuracy of brain PMCT for SAH and to identify the characteristics of pseudo-SAH. Findings on PMCT (sulcal effacement, asymmetry, maximum thickness of SAH signs, presence of acute/subacute intraventricular/intraparenchymal hemorrhage) and clinical history (left ventricular assist device [LVAD] implantation, anticoagulation therapy/coagulation disorder, global ischemia) were compared between subjects with true SAH and those with pseudo-SAH. Twenty eight of 128 enrolled subjects had positive signs of SAH on PMCT, 20 (71.4%) had SAH on autopsy, and 8 (28.6%) did not. The sensitivity, specificity, positive predictive value, and negative predictive value of SAH signs seen on PMCT were 95.2, 94.6, 71.4, and 99.3%, respectively. Asymmetry of SAH signs and acute/subacute intraventricular and intraparenchymal hemorrhage were significantly more common in true SAH cases than in pseudo-SAH cases. The maximum thickness of SAH signs was significantly greater in true SAH cases. A history of LVAD implantation, anticoagulation therapy, and/or a coagulation disorder were more common in true SAH cases but not significantly so. A history of global ischemia was significantly more common in pseudo-SAH cases. If signs of SAH are observed on PMCT, it is important to look for other signs on PMCT and carefully review the clinical history to avoid a diagnostic error.