FOR 12 years, the man in front of me lived with Parkinson鈥檚: he had a stammer; he dragged his left foot. At 79, his mental faculties were slowing 鈥� but strangely, he didn鈥檛 have the tremors we normally associate with the disease.
When I say he is in front of me, what I mean to say is that his central nervous system 鈥� his brain and spinal column 鈥� is laid out before me. I am in a dissection room at the Division of Brain Sciences, Imperial College London.
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Neuropathologist rotates the man鈥檚 brain in his gloved hands. With a scalpel he removes the olfactory bulb at the base 鈥� sometimes this is smaller in Parkinson鈥檚 patients, and if it is, they lose their sense of smell. Gentleman points out a slight thickening in the cranial carotid artery, one of the main blood supplies to the brain. 鈥淎 bit of atherosclerotic build-up, to be expected in a man of this age.鈥�
Next, Gentleman locates a couple of bits of tissue under the brain called the . Using them as a kind of grid reference, he slices the brain in two with what resembles a large bread knife. It opens like a walnut.
鈥淪traight away I can see that the ventricles are very wide,鈥� says Gentleman, who has dissected around 1000 brains in his career. 鈥淚t is consistent with the long progression of the disease.鈥�
In the laboratories around us is a small but valuable bank into which about 900 people have made a deposit 鈥� one might say the ultimate deposit. The contains more than 100,000 individual samples of frozen brain tissue. Some 9000 people have pledged to donate their central nervous systems when they die. The bodies are returned to families for funerals; even an open casket funeral is possible as the brain and spinal cord are removed from the back.
Neuroscientists from around the world apply to the bank for samples, and if successful, they only have to pay for postage. 鈥淭here鈥檚 a growing demand, as animal models aren鈥檛 mirroring the diseases too well,鈥� says , director of the bank.
Parkinson鈥檚 disease affects 1 in 1000 people, and in the over-60s, 1 in 100. Multiple sclerosis on the other hand is more likely in younger adults, affecting between 2 and 150 people per 100,000. Both are debilitating neurodegenerative disorders. Drugs can treat the symptoms but in both cases the underlying trigger is unknown. Damage to the insulating cell sheaths in MS cannot be halted or reversed, nor can the death of dopamine-producing cells that are a hallmark of Parkinson鈥檚. 鈥淭he holy grail is to develop neuroprotection,鈥� says Dexter.
That is what Dexter is working towards. In his latest publication, he and colleagues examined brain bank tissue and found that the X chromosome is less active in the brains of people with neurological disorders (, ). Dexter also wants to look at links between epigenetic factors and disease. These chemical modifications of DNA play an important part in controlling how genes are expressed. From donated brain tissue, Dexter has found that part of the epigenetic modification system can inhibit the tightening of the coils of DNA. This seems to protect against Parkinson鈥檚.
鈥淎s we live longer, more and more of us are going to be affected,鈥� Dexter says. 鈥淚f you look at the 鈥榥ormal鈥� brains that come into the bank, about 15 per cent actually aren鈥檛 normal 鈥� they鈥檝e got early stages of a neurodegenerative disease.鈥�
Thirty minutes or so later, Gentleman has finished the dissection. Brain tissue is spread out over the table in neat 10 millimetre slices, like some kind of macabre deli counter. 鈥淭he convolutions of the brain are like fingerprints 鈥� no two are the same,鈥� he says. 鈥淭hese were individuals. I still see it as a privilege to dissect them. But I have to have a practical disconnect, and I still have no idea how a pile of fat 鈥� a lot of lipid membranes 鈥� can represent a person.鈥�
鈥淏rain tissue is spread over the table in neat 10 mm slices like some kind of macabre deli counter鈥�
This article appeared in print under the headline 鈥淵our brain in their hands鈥�
