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Microsurgical Resection of Tumor of the Lateral Ventricle:

The surgical management of tumors of the lateral ventricles (LV) and the third ventricle (TV) remains a distinct challenge for neurosurgeons due to the deep and difficult-to-reach location and frequent involvement of adjacent critical neurovascular structures. An appropriate surgical approach should provide adequate operative working space with minimal brain retraction or brain transgression. To accomplish these goals, neurosurgeons may choose an approach that necessitates a longer distance to reach the tumor if it minimizes the amount of brain tissue that is resected or placed at risk by the approach. Furthermore, selection of the optimal approach to ventricular tumors depends on multiple other factors including the size of the ventricles and the tumor, the location of the arterial supply, pathological features of the tumor, and the surgeon’s experience. This video provides an overview of the open surgical operative corridors to the lateral tumors, highlighting the key surgical principles.

Transsexuality

Taken from D. F. Swaab’s book We Are Our Brains:

Transsexuals feel that they have been born into a body of the wrong gender and are desperate for a sex change or gender reassignment. This is a gradual process that starts with an individual adopting the social role of the opposite sex and taking hormones, then undergoing a series of extensive operations—which only 0.4 percent later regret. The first person in the Netherlands to respond to the plight of transsexuals was Otto de Vaal, an endocrinologist and pharmacologist who taught at the University of Amsterdam. He treated them for free starting in 1965, feeling that his university pay was sufficient. The gender team of the VU University Medical Center in Amsterdam (VUmc) subsequently took on a pioneering role, headed first by Louis Gooren and now by Peggy Cohen-Kettenis. That’s remarkable in itself because the Vrije Universiteit was established as a Calvinist university, and the Bible does say: “A woman shall not wear man’s clothing, nor shall a man put on a woman’s clothing; for whoever does these things is an abomination to the Lord your God” (Deuteronomy 22:5–6).

Since 1975, 3,500 people have undergone gender reassignment at the VUmc. The first time I learned about transsexuality was as a medical student in the 1960s. Coen van Emde Boas, a professor of sexology, entered the lecture room of the obstetrics and gynecology department with a bearded man. It wasn’t exactly the place you would expect a man to be demonstrating anything. But he turned out to be a genetic woman, a female-to-male transsexual. This made a deep impression on me, and set me thinking about the possible underlying mechanism.

Male-to-female transsexuality (MtF) occurs in 1 in 10,000 individuals, and female-to-male transsexuality (FtM) in 1 in 30,000. Gender problems tend to become apparent from an early age. Mothers typically relate how their little boys dressed up in their frocks and shoes, were only interested in girls’ toys, and mainly played with girls. But not all children with gender problems want to change sex later. If necessary, puberty can be delayed with the help of hormones to gain extra time in which to decide whether or not to undergo treatment.

All the data indicates that gender problems arise in the womb. Tiny variations in genes associated with the effect of hormones on brain development have been found to increase the likelihood of transsexuality. It can also be increased by abnormal fetal hormone levels or by medication taken during pregnancy that inhibits the breakdown of sex hormones. The differentiation of our sex organs takes place in the first months of pregnancy, while the sexual differentiation of the brain occurs in the second half of pregnancy. Since these two processes take place at different times, the theory is that in the case of transsexuality, they have been influenced independently of one another. If this is the case, one would expect to find female structures in the brains of MtF transsexuals and vice versa in the case of FtM transsexuals. In 1995 we indeed found, in postmortem studies of donor brains, a small structure in which the usual sex difference was reversed. We published our findings in Nature. The brain structure in question is the bed nucleus of the stria terminalis (BST), an area that’s involved in many aspects of sexual behavior (figs. 10 and 11). The central part of this nucleus, the BSTc, is twice as large in men as in women and contains twice as many neurons. We found MtF transsexuals to have a “female” BSTc. The only FtM transsexual we could study—the material in question being yet rarer than the brains of MtF transsexuals—indeed proved to have a “male” BSTc. We were able to rule out the reversal of the sex difference in transsexuals being caused by altered hormone levels in adulthood, so the reversal must have happened at the developmental stage.

If you publish something truly interesting, the nicest thing you’ll probably hear your colleagues say is, “It’ll need to be confirmed by an independent research group.” And that can take a while, because it took me twenty years to collect the brain material for my study. So I was delighted when in 2008 the group headed by Ivanka Savic in Stockholm published a study involving functional brain scans of living MtF transsexuals. They had not yet been operated on, nor given hormones. As a stimulus they were given male and female pheromones, scents that aren’t consciously perceived. In control groups, these were shown to produce different patterns of stimulation in the hypothalamus and other brain areas in men and women. The stimulation pattern for MtF transsexuals fell between that of men and women.

In 2007 V. S. Ramachandran published an interesting hypothesis and provisional research findings on transsexuality. He believes that the neural body map of MtF transsexuals lacks a penis, while that of FtM transsexuals lacks breasts, due to these not being programmed into the map during development. As a result, they don’t recognize these organs as their own and want to get rid of them. So everything indicates that the early development of sexual differentiation in the brains of transsexuals is atypical and that they aren’t, in fact, simply psychotic, as a Dutch psychiatrist was impertinent enough to claim recently. At the same time it is of course essential, before initiating treatment, to make sure that the desire to change sex isn’t part of a psychosis, as it can be an occasional symptom of schizophrenia, bipolar depressions, and serious personality disorders.

FIGURE 10. Located at the tip of the lateral ventricle (1) is the bed nucleus of the stria terminalis (BST), a region of the brain important for sexual behavior.


FIGURE 11. The central part of the bed nucleus of the stria terminalis (BSTc) (see fig. 10 for location) is twice as big in men (A, C) and contains twice as many neurons as in women (B). In male-to-female transsexuals we found a female BSTc (D). The only female-to-male transsexual we could study (these brains being rarer than those of MtF transsexuals) indeed proved to have a male BSTc. This reversal of the sex difference in transsexuals corresponds with their gender identity (the feeling of being a man or woman) rather than with their chromosomal sex, or the sex on their birth certificate. LV = lateral ventricle, BSTm = medial section of the BST. J-N Zhou et al., Nature 378 (1995): 68–70

Researchers observe stem cell specialization in the brain

Adult stem cells are flexible and can transform themselves into a wide variety of special cell types. Because they are harvested from adult organisms, there are no ethical objections to their use, and they therefore open up major possibilities in biomedicine. For instance, adult stem cells enable the stabilization or even regeneration of damaged tissue. Neural stem cells form a reservoir for nerve cells. Researchers hope to use them to treat neurodegenerative disorders such as Parkinson’s and Alzheimer’s disease. Tübingen researchers led by Professor Olga Garaschuk of the University of Tübingen’s Institute for Physiology, working with colleagues from Yale University, the Max Planck Institute of Neurobiology in Martinsried and the Helmholtz Center in Munich, studied the integration of these cells into the pre-existing neural network in the living organism. The results of their study have been published in the latest edition of Nature Communications.

There are only two places in the brains of adult mammals where stem cells can be found – the lateral ventricles and the hippocampus. These stem cells are generating neurons throughout life. The researchers focused on a stem cell zone in the lateral ventricle, from where progenitors of the nerve cells migrate towards the olfactory bulb. The olfactory nerves which start in the nasal tissue run down to this structure, which in mice is located at the frontal base of the brain. It is there that the former stem cells specialized in the task of processing information on smells detected by the nose. “Using the latest methods in microscopy, we were for the first time able to directly monitor functional properties of migrating neural progenitor cells inside the olfactory bulb in mice,” says Olga Garaschuk. The researchers were able to track the cells using special fluorescent markers whose intensity changes according to the cell’s activity.

The study showed that as little as 48 hours after the cells had arrived in the olfactory bulb, around half of them were capable of responding to olfactory stimuli. Even though the neural progenitor cells were still migrating, their sensitivity to odorants and their electrical activity were similar to those of the surrounding, mature neurons. The mature pattern of odor-evoked responses of these cells strongly contrasted with their molecular phenotype which was typical of immature, migrating neuroblasts. “Our data reveal a remarkably rapid functional integration of adult-born cells into the pre-existing neural network,” says Garaschuk, “and they show that sensory-driven activity is in a position to orchestrate their migration and differentiation as well as their decision of when and where to integrate.”