Brain Death Diagnosis in Primary Posterior Fossa Lesions

Abstract

Background: New controversies have raised on brain death (BD) diagnosis when lesions are localized in the posterior fossa.

Objective: The aim of this study was to discuss the particularities of BD diagnosis in patients with posterior fossa lesions.

Materials and methods: The author made a systematic review of literature on this topic.

Results and conclusions: A supratentorial brain lesion usually produces a rostrocaudal transtentorial brain herniation, resulting in forebrain and brainstem loss of function. In secondary brain lesions (i.e., cerebral hypoxia), the brainstem is also affected like the forebrain. Nevertheless, some cases complaining posterior fossa lesions (i.e., basilar artery thrombotic infarcts, or hemorrhages of the brainstem and/or cerebellum) may retain intracranial blood flow and EEG activity. In this article, I discuss that if a posterior fossa lesion does not produce an enormous increment of intracranial pressure, a complete intracranial circulatory arrest does not occur, explaining the preservation of EEG activity, evoked potentials, and autonomic function. I also addressed Jahi McMath, who was declared braindead, but ancillary tests, performed 9 months after initial brain insult, showed conservation of intracranial structures, EEG activity, and autonomic reactivity to "Mother Talks" stimulus, rejecting the diagnosis of BD. Jahi McMath's MRI study demonstrated a huge lesion in the pons. Some authors have argued that in patients with primary brainstem lesions it might be possible to find in some cases partial recovery of consciousness, even fulfilling clinical BD criteria. This was the case in Jahi McMath.

Keywords: Ancillary tests; Brain death; EEG; Jahi McMath; brain-dead; brainstem lesions; cerebral blood flow (CBF); posterior fossa.