Figure 15:
Retained intracranial activity from a previous study in the presence of brain death.
19 y/o male s/p MVA with closed head injury, cerebral edema and downward herniation.

A. This case is an example of the problem encountered when repeating the study in less than twenty-four hours. Initial ECD flow study demonstrates persistent intracranial perfusion, left greater than right.

B. Static images demonstrate absence of activity in the region of the right inferior temporal lobe, which may represent focal cut-off in blood supply due to herniation (arrow).

C. Cerebral edema involving the right hemisphere greater than the left associated with the right sided SAH and SDH is noted on axial CT images.

D. Subsequent ECD flow study performed 17 hours later shows diffuse intracranial activity from the first frame without evidence of new perfusion indicating that this represents residual activity from the initial study (arrow)

E. Static images demonstrate intracranial activity, which could be misinterpreted as cerebral metabolism without comparison to the flow study (arrow). Additionally, intracranial activity is significantly less than that seen extracranially indicating that blood flow is being shunted via the ECA's to the face and scalp.

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