Tae Jin Yun
Brain death is a clinical diagnosis. Cardinal requirements for clinical determination of brain death include coma, absence of brain stem reflexes, and apnea.1 Although confirmatory tests, also known as ancillary tests, are not mandatory in most situations, additional tests may be necessary for declaration of brain death in patients whose specific components of clinical testing cannot be reliably evaluated.2
Confirmatory tests for brain death can be divided into those demonstrating loss of bioelectrical activity and those showing absence of cerebral blood flow. As preferred confirmatory tests to demonstrate the absence of cerebral blood flow, cerebral angiography or radiotracer methods have been used.3 However, cerebral angiography is invasive, with risk of vessel injury. Furthermore, both angiography and radiotracer methods not only require an injection of exogenous material, such as contrast media or radioisotopes, they also cause additional exposure to radiation. Understandably, grieving family members are occasionally against any invasive test to confirm brain death. In addition, the concept of brain death is often difficult for families to accept when dealing with a tragic loss. Hence, easily applied clinical tools that enable patients’ kin to understand brain death are needed.
Recently, arterial spin-labeling (ASL) has been incorporated as a part of the protocols for perfusion MR imaging. We have encountered consistent appearances of ASL perfusion-MR images in patients with brain death as follows: 1) extremely decreased perfusion in the whole brain; 2) bright vessel signal intensity around the entry of the carotid artery to the skull, which represents an arrested labeled blood, presumably secondary to elevated intracranial pressure; 3) patent external carotid circulation; and 4) “hollow skull sign,” which represents a finding of extremely impaired cerebral perfusion with preserved perfusion in the distribution of the