Thank you very much to Dr. Revuelto Rey and Egea-Guerrero for interest in the image-based case. In these types of submissions, there is usually no room for detailed explanations; fortunately, here there is room to do so.

The use of transcranial Doppler (TCD) is widely accepted in many countries for the assessment of the “intracranial” artery flow when evaluating for cerebral circulatory arrest (CCA). For this indication, Doppler insonation of middle cerebral arteries (MCA) as well as basilar artery (BA)/intracranial vertebral arteries is preferred over transorbital insonation of the intracranial (carotid siphon) internal carotid artery (ICA) or transcervical (extracranial) ICA insonation.1 While the insonation of extracranial ICA and transorbital ICA has shown a high specificity for diagnosing CCA, this finding comes up late in comparison with insonation of MCA and BA,2 thus requiring serial examinations and long observation periods, as seen in the case presented. This obviously means that when an early confirmation of brain death is mandatory (for example, in organ donation), the isolated use of extracranial artery or transorbital insonation is not probably the best option.2

From another perspective, ultrasound is nearly all we have in many small centers as an ancillary test for confirming brain death and many intensivists give up when they cannot find an MCA and BA flow. This is probably the most important point of the case, teaching that extracranial artery insonation is feasible and reliable, showing the same flow CCA patterns (although in a late fashion and this must be especially remembered) as insonation of intracranial arteries and useful when no other ancillary test is available.

This work has not been presented at any conferences.

This work has not been supported by any grants.

Author has no conflicts of interest related to this submission.