Practical Pearl: Use of MRI to Differentiate Pseudo-subarachnoid Hemorrhage from True Subarachnoid Hemorrhage

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.

Basal Cistern Effacement and Pseudo-Subarachnoid Hemorrhage on Computed Tomography Images of Chronic Subdural Hematoma

OBJECTIVE

Computed tomography images of patients with chronic subdural hematoma (CSDH) sometimes show obliteration of the basal cistern with high density in an obliterated Sylvian cistern, termed pseudo-subarachnoid hemorrhage (SAH). The present study aimed to clarify the characteristics and outcomes of these conditions.

METHODS

We retrospectively investigated 669 consecutive patients who were surgically treated for CSDH between January 2006 and May 2019.

RESULTS

Basal cistern effacement and pseudo-SAH were found in 24 (3.6%) and 11 (1.6%) patients, respectively. Predictors of basal cistern effacement in patients with CSDH were younger age, cerebrospinal fluid leak, and bilateral CSDH (P < 0.05). In patients with basal and Sylvian cistern effacement, the significantly different main features to differentiate patients with and without pseudo-SAH were younger age, cerebrospinal fluid leak, and thick small hematomas on computed tomography slices of the Sylvian cistern (P < 0.05). Magnetic resonance imaging showed that high-density areas in the Sylvian cistern of pseudo-SAH on precontrast computed tomography images corresponded to the M1 segment of the middle cerebral artery. The outcomes of patients with basal cistern effacement and of patients with pseudo-SAH did not differ from other patients with CSDH, although rates of surgical complications were significantly higher among patients with basal cistern effacement.

CONCLUSIONS

Although the outcomes of patients with basal cistern effacement and pseudo-SAH were similar to outcomes of other patients with CSDH, problematic postsurgical complications and cerebrospinal fluid leaks were more likely to arise in such patients.