Question

Patient found pulseless after submersion in water for 20 minutes.  After ROSC, patient’s GCS was 3 and pupils are dilated and nonreactive.

Answer

• There is increased attenuation of the basal cisterns and subarachnoid space as well as diffuse cerebral edema.
• At first glance, it appears to be a subarachnoid hemorrhage.
• However, the Hounsfield unit of the density is lower than blood.
• This is a pseudosubarachnoid hemorrhage sign.  
• This can be seen in anoxic injury with cerebral edema, pyogenic meningitis, venous sinus thrombosis, bilateral large subdural hemorrhages.

References

Kim JM, Eom TH. The pseudosubarachnoid hemorrhage: clinical implications of subarachnoid hemorrhage misdiagnosis. Pediatr Emerg Care. 2016 May 12. [Epub ahead of print]