Neuroscience  

A new study using intricate fiber dissection techniques provides new insights into the deep anatomy of the human brain-stem.  This work helps to define 'safe entry zones' for neurosurgeons performing brain-stem surgery.

A study using intricate fiber dissection techniques provides new insights into the deep anatomy of the human brain-stem—and helps to define "safe entry zones" for neurosurgeons performing brain-stem surgery, according to a special article published in Operative Neurosurgery, a quarterly supplement to Neurosurgery, official journal of the Congress of Neurological Surgeons.

Neurosurgeons Dr. Kaan Yagmurlu and Dr. Albert L. Rhoton, Jr, of University of Florida, Gainesville, and colleagues performed fiber tract dissections, along with three-dimensional photography, to explore and document the complex anatomy of the brain-stem. "We hope that the use of this knowledge will make surgical entry into the brainstem more accurate and safe," Dr. Rhoton and coauthors write.

"We hope that the use of this knowledge will make surgical entry into the brainstem more accurate and safe."

Working under the operating microscope, the researchers performed meticulous dissections of human brain-stem specimens. They used a technique called fiber tract dissection, which traces the complex course of the nerve fibers that make up the brain-stem. At each step of the dissection, 3D photographs were obtained. In some areas, a magnetic resonance imaging technique called diffusion tensor imaging was used to help in visualizing the nerve fiber tracts.

The lowermost portion of the brain is directly connected to the spinal cord. The brain-stem is involved in regulating some of the body's most basic functions. In addition to mapping and illustrating the inner anatomy of the brain-stem, the researchers sought to identify the best surgical approaches to specific brain-stem areas.

In their article, Drs. Yagmurlu and Rhoton and colleagues present richly detailed descriptions and 3D images of the fiber tract anatomy of the brain-stem. They also propose a short list of "safe entry zones" for each of the three major portions of the brain-stem: the midbrain, pons, and medulla.

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For each area, the suggested routes include key anatomical landmarks for the neurosurgeon to follow. The fundamental principle is to pass through as little normal tissue as possible, while avoiding critical areas and tracts.

"The safest approach for lesions located below the surface is usually the shorter and most direct route," the researchers write. However, for some parts of the brain-stem, a more circuitous approach is needed to reach the target while protecting essential functional areas.

Although previous studies have used fiber dissection techniques to examine safe entry zones to the brain-stem, most have focused on the surface anatomy. The new study is the first to use these techniques to define and document the "complex internal architecture" of the brain-stem.

Drs. Yagmurlu and Rhoton and coauthors note that their dissection study cannot account for the infinite variations in anatomy of the human brain-stem—the use of neurophysiological monitoring and mapping remains crucial during surgery. However, by providing unprecedented descriptions and 3D images of the inner anatomy of the brain-stem, the researchers hope their work will help neurosurgeons in planning the best approach to microsurgical procedures for gliomas (brain cancers) and blood vessel malformations in each area of the brain-stem.


SOURCE  Medical Xpress

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 Medical Breakthrough  

An Italian neurosurgeon believes doctors now have the technical means to transplant human heads. The procedure, which has previously been performed on monkeys, could be used to replace one human head with another due to recent advancements in cell and nerve research that make it possible to reconnect spinal cords.

Tthe medical and technical barriers to grafting one person’s head onto another person’s body, just as in Mary Shelly's Frankenstein, may now be overcome, says Italy's Dr. Sergio Canavero.

Canavero, a member of the Turin Advanced Neuromodulation Group wrote in a recent paper, how a procedure modeled on successful head transplants which have been carried out in animals since the 1970's by Dr. R.J. White, may clear up the remaining challenges of those experiments.

The project proposal published by the medical journal Surgical Neurology International, has been dubbed by Canavero, “Head Anastomosis Venture” – or HEAVEN.
The main problem with head transplants was that scientists were unable to connect the animals’ spinal cords to their donor bodies, leaving them paralyzed below the point of transplant.

Canavero now says that recent advances in re-connecting spinal cords that are surgically severed mean that it should be technically feasible to do it in humans.

Drawing depicting the first total cephalosomatic exchange in a monkey (from White et al. 1971)

The procedure Canavero outlines is very much like that used by White, who successfully transplanted the head of a rhesus monkey onto the body of a second rhesus in 1970. First, both patients must be in the same operating theater. Then the head to be transplanted must be cooled to between 12°C and 15°C (54.6°F and 59°F). Moving quickly, surgeons must remove both heads at the same time, and re-connect the head to be preserved to the circulatory system of the donor body within one hour. During the re-connection procedure, the donor body must also be chilled, and total cardiac arrest must be induced.

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Once the head is reconnected, the heart of the donor body can be re-started, and surgeons can proceed to the re-connections of other vital systems, including the spinal cord.

White said in a documentary about the procudeure, "We had done something - good or bad -that was monumental."
Connection of a spinal cord from the head of one creature to the body of another has never been attempted even in animals, so Canavero’s paper must be taken as an exercise in speculation. However, the severing and re-connection of spinal cords in the same animal has met with limited success in the past.

The re-connection of spinal cords can be accomplished through the encouragement of the body’s natural healing mechanisms, which are at work even in the severed spinal cord. But Canavero’s proposal is different: By cutting spinal cords with an ultra-sharp knife, and then mechanically connecting the spinal cord from one person’s head with another person’s body, a more complete (and immediate) connection could be accomplished. As he notes in his paper:

It is this “clean cut” [which is] the key to spinal cord fusion, in that it allows proximally severed axons to be ‘fused’ with their distal counterparts. This fusion exploits so-called fusogens/sealants….[which] are able to immediately reconstitute (fuse/repair) cell membranes damaged by mechanical injury, independent of any known endogenous sealing mechanism.

Depiction of various ways to locally cord the spinal cord (from Negrin 1973)

Canavero hypothesizes that plastics like polyethylene glycol (PEG) could be used to accomplish this fusing, citing previous research showing that, for example, in dogs PEG allowed the fusing of severed spinal cords.

Dr Canavero concludes by saying “body image and identity issues will need to be addressed, as the patient gets used to seeing and using the new body”.

He said: “HEAVEN appears to have grown into a feasible enterprise early in the 21st century,” but added that he has not considered the ethical implications of his proposal.

What do you think?  Is Canaverro the modern Prometheus, or is this work bad science?

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