Neuropathology of brain death in the modern transplant era

Autopsy studies in patients who have been declared brain dead are rare. Total brain necrosis ("respirator brain") has been a common finding in the distant past. The time to brain fixation has been shortened as a result of timely organ transplant protocols, therefore the neuropathologic findings may be different than previously described.

We reviewed macroscopic and microscopic brain pathology for ischemic neuronal damage in 41 patients who fulfilled the clinical criteria of brain death. Hematoxylin and eosin stained brain tissue slides were retrieved and available wet tissue was additionally stained to complete a series of samples of the hemispheres, brainstem, and cerebellum for each patient. Neuronal ischemic change was semiquantitatively graded for severity (mild 0 to 5%, moderate >5 to 75%, and severe >75%).

After the clinical diagnosis of brain death and terminal cardiac arrest, 12 brains were fixated in less than 12 hours and 29 brains were fixated between 12 and 36 hours. The frontal lobe, temporal lobe, parietal lobe, occipital lobe, and basal ganglia showed moderate to severe ischemic change in 53 to 68% of the cases. Moderate to severe neuronal ischemic change was found in the thalamus in 34%, midbrain in 37%, pons in 41%, medulla in 40%, and cerebellum in 52% of the cases.

No distinctive neuropathologic features were apparent in our series of patients with brain death. Neuronal ischemic changes were frequently profound, but mild changes were present in a third of the examined hemispheres and in half of the brainstems. Respirator brain with extensive ischemic neuronal loss and tissue fragmentation was not observed. Neuropathologic examination is therefore not diagnostic of brain death.