- A diagnosis of brain death relies on specific clinical criteria. For example, the neurological examination must demonstrate absent cortical and brainstem function.
- When standard clinical criteria cannot be applied, such as in a case where cranial nerves cannot be reliably examined, ancillary tests may be used to confirm the diagnosis.
- Cerebral arteriography can be used to document the presence (or absence) of cerebral blood flow. When intracranial pressure rises above cerebral perfusion pressure there is no further detectable blood flow to the intracranial circulation.
CT head shows the prior right-sided decompressive hemicraniectomy and the large left-sided subdural hematoma with nearly 3 cm left-to-right midline shift. There is profound transtentorial herniation and brainstem compression.
Right common carotid artery injection demonstrates brisk filling of the external carotid artery (feeding the scalp and face). However, there is only sluggish flow through the extracranial segment of the right internal carotid artery and no detectable flow to the intracranial circulation.
Note the "flame shape" in the extracranial segment of the internal carotid artery. The flame shape is a flow related phenomenon. It is caused by a stagnant column of unopacified blood that impedes migration of contrast into the actually patent extracranial internal carotid artery segment. Due to laminar flow, which is maximal centrally, the flow that does push farthest is in the middle, creating the appearance of a tapered flame.