Pseudosubarachnoid hemorrhage

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Pseudo-subarachnoid haemorrhage is the a sign related to apparent increased attenuation within the basal cisterns which simulates a true subarachnoid haemorrhage (SAH).

Pathology

AssociationsCauses and associations

~~recent resuscitation from cardiopulmonary arrest:~~~~decreases~~
The most common cuase is cerebral oedema where there is a decrease in parenchyma attenuation ~~due~~ ~~cerebral oedema~~ ~~and engorgement~~and engorgement and dilatation of the superficial venous structures due anincreased intracranial pressure. ^1,2

This is seen in anoxia and recent resuscitation from cardiopulmonary arrest.

Other causes include:

severe meningitis: breakdown of the blood brain barrier allowing mildly hyperdense proteinaceous material to leak into the subarachnoid space ³
venous sinus thrombosis
bilateral large subdural haemorrhage producing effacement of sulci and basilar cisterns and the false impression of blood in the subarachnoid space ⁵
intrathecal contrast

Radiographic features

CT

usually symmetrical density confined to basal cisterns (i.e. no sulcal density)
30-40 HU (compared with true acute SAH ~ 60HU)
often seen with generalised cerebral oedema or basal cistern effacement
the appearances thought due to combination of
- cisternal effacement
- distention +/- thrombosis of vessels
- adjacent ~~brain~~ brain hypoattenuation accentuating contrast difference

Given et al. reviewed 7 cases of generalised cerebral oedema accompanied by increased basal cisternal attenuation which were all found not to have ~~subarachnoid~~ subarachnoid blood at at lumbar puncture or autopsy¹.

Differential diagnoses

true subarachnoid haemorrhage
acute leptomeningitis mimicking a subarachnoid haemorrhage ³

-<p><strong>Pseudo-subarachnoid haemorrhage</strong> is the a sign related to apparent increased attenuation within the basal cisterns which simulates a true <a href="/articles/subarachnoid-haemorrhage">subarachnoid haemorrhage</a> (SAH).</p><h4>Pathology</h4><h5>Associations</h5><ul>
-<li>recent resuscitation from cardiopulmonary arrest:<sup> </sup>decreases in parenchyma attenuation due <a href="/articles/cerebral-oedema-1">cerebral oedema</a> and engorgement and dilatation of the superficial venous structures due an <a href="/articles/increased-intracranial-pressure">increased intracranial pressure</a> <sup>1,2</sup>
~~-</li>~~
-<li>severe <a href="/articles/leptomeningitis">meningitis</a>: breakdown of the <a href="/articles/blood-brain-barrier">blood brain barrier</a> allowing proteinaceous material to leak into the <a href="/articles/subarachnoid-space">subarachnoid space</a> <sup>3</sup>
+<p><strong>Pseudo-subarachnoid haemorrhage</strong> is the a sign related to apparent increased attenuation within the basal cisterns which simulates a true <a href="/articles/subarachnoid-haemorrhage">subarachnoid haemorrhage</a> (SAH).</p><h4>Pathology</h4><h5>Causes and associations</h5><p>The most common cuase is <a href="/articles/cerebral-oedema-1">cerebral oedema</a> where there is a decrease in parenchyma attenuation and engorgement and dilatation of the superficial venous structures due an <a href="/articles/increased-intracranial-pressure">increased intracranial pressure</a>. <sup>1,2 </sup>This is seen in anoxia and recent resuscitation from cardiopulmonary arrest.</p><p>Other causes include:</p><ul>
+<li>severe <a href="/articles/leptomeningitis">meningitis</a>: breakdown of the <a href="/articles/blood-brain-barrier">blood brain barrier</a> allowing mildly hyperdense proteinaceous material to leak into the <a href="/articles/subarachnoid-space">subarachnoid space</a> <sup>3</sup>
+<li>intrathecal contrast</li>
~~-<li>adjacent brain hypoattenuation accentuating contrast difference</li>~~
+<li>adjacent brain hypoattenuation accentuating contrast difference</li>
-</ul><p>Given et al. reviewed 7 cases of generalised cerebral oedema accompanied by increased basal cisternal attenuation which were all found not to have subarachnoid blood at lumbar puncture or autopsy <sup>1</sup>.</p><h4>Differential diagnoses</h4><ul>
+</ul><p>Given et al. reviewed 7 cases of generalised cerebral oedema accompanied by increased basal cisternal attenuation which were all found not to have subarachnoid blood at lumbar puncture or autopsy <sup>1</sup>.</p><h4>Differential diagnoses</h4><ul>

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