Cryopreservation of just the head is as old as Alcor itself. In fact, some people identify Alcor with its “neuro-preservation” option. It is important, however, to recognize that the objective of preserving the head is really to preserve what is inside the head, i.e. the brain. While I am aware of (contrived) technical arguments that prefer head preservation over brain preservation for information-theoretical reasons, I suspect that no advocate of neuro-preservation is anxious about the prospect of having only his/her brain preserved in a pristine state.
This raises an important question – one that is not immediately evident to the general public. Why not just preserve the naked brain instead? I am aware of at least three major arguments against it and I think that these arguments are based on incomplete information or a lack of imagination.
Myth 1: The isolated brain is not a stable organ and will collapse upon itself in a jellylike state if it is removed from the skull.
Answer: In human cryopreservation the brain would only be extracted at low temperatures which provide a lot more stability to the brain. In addition, in a good case the brain will also be loaded with a cryoprotectant and exist in a dehydrated state, which will provide even more stability.
Myth 2: Removing the brain from the skull will damage the brain and will erase identity-critical information.
Answer: It is correct that morticians typically remove the brain with little regard for its ultrastructural integrity but there is no reason why a cryonics organization should engage in such traumatic brain removal. Safe brain removal protocols are technically possible and cryonics organizations have a strong incentive to develop and refine such techniques.
Myth 3: The skull is necessary to provide protection to the brain.
Answer: It is undeniable that the skull provides robust protection to the brain but from that it does not follow that a cryonics organization cannot design a long-term enclosure and maintenance method that provides strong protection of the naked brain, too.
I do not claim that brain preservation is equal in all respects to neuro-preservation. For example, extraction of the brain from the skull requires additional time after completion of cryoprotectant perfusion and during this time the brain will be exposed to high levels of cryoprotectant (strictly speaking, isolated brain perfusion is possible but this requires a very advanced surgical procedure). Keeping the brain temperature low and uniform during brain removal is also a challenge.
On the other hand, there are potential advantages as well. An isolated brain can be placed in the cryoprotectant to allow diffusion of the vitrification agent prior to cryogenic cooldown to compensate for any ischemia-induced cortical perfusion impairment. In fact, if perfusion is no longer an option, immersion of the (fixed) brain in cryoprotectant is the only means to mitigate ice formation during cryostasis. Another advantage is a decrease in long-term care costs (at least 50%), which allows for lower cryopreservation minimums.
But the most important advantage of brain preservation is that public perception and negative PR would be substantially lower than that with neuro-preservation. Even if the procedure were a little riskier (technically speaking) one could still argue that it is safer in general because images of cryopreserved brains do not risk the kind of visceral response that neuro-preservation triggers.
I cannot do justice to all the technical, logistical, and financial issues associated with brain-only cryopreservation here but the topic requires more study for the reason alone that cryonics organizations occasionally receive fixed brains, or patients with long ischemic times, for whom immersion cryoprotection could be superior to straight freezing. Brain cryopreservation does not exist as an option yet, but it has been the reality for a number of patients.
Originally published as a column (Quod incepimus conficiemus) in Cryonics magazine, January, 2014