Chemo-and radiotherapy’s nervous system impairing side effects
(The polysaccharides and other possibilities in, order to decrease the side effects II.) It’s our conviction that we can only decrease the possible serious side effects of certain therapies if we know them. Chemo-and radiotherapy’s one less known long term side effect is its effects on the nervous system.
In 2005 an experiment compared the mental state of 702 people over 65 who survived cancer with their siblings. The researchers came to the conclusion that the cancer survivors are highly endangered due to the long term formation of mental disorders. 14.5% of the cancer survivors had a mental disorder only but only 8.7% of their healthy siblings suffered from this problem.
Researchers suggest counting on this risk as well when they choose the appropriate treatment. The direct brain irradiation’s side effects are well-known. A detailed study about the chemotherapy’s brain-damaging effects’ mechanism was published only at the end of the year. To get the damaging mechanisms at first we have to take a look at the last 10 years’ brain research results. The most stubborn dogma of the 20th century brain research according to which, the developed brain new brain cells didn’t develop till during the last decade. At least in the hippocampus (gyrus dentatus) and in the so called subventricular zone constant brain cell formation happens till the end of human life. A part of the brain cells survive in the hippocampus become functional and integrates to the already existing brain cell network. The number of new cells is very low compared to the previously existing brain cells’ but its philosophical characters differ from the previously formed neurons’. They activate much quicker than their previous companions. The new cells take place in the hippocampus’ ‘bottle-neck’ so they decisively influence the functioning of the memory and thinking centre. If the formation of these new neurons is hindered serious mental diseases can form, such as depression, mental disability, dementia and schizophrenia. Fostering the formation of neurons can improve the mood and the cognitive performance as well. Most of the licensed medications against depression foster the formation of new neurons in the hippocampus and if this neurogenesis triggered by the medications is hindered the medications don’t lessen the depression’s symptoms. So researchers came to the conclusion that the medication’s antidepressant effect can be led back to their neuron formation fostering effect. The increase of the activation of the hippocampus also fosters the formation of new neurons.
A new discovery is that the hippocampus is a vital organ of language learning. If the brain gets hurt the hippocampus is the organ which diverts the functioning of the language centres from the hurt one to another intact area. The neural progenitor cells in the hippocampus are the most vulnerable, their permanent injuries can lead to mental and physical abnormality.
A study carried out in 2006 using animal experiments came to the conclusion that the usage of chemotherapy can also impair the neural stem cells in the hippocampus. 18% of women suffering from breast cancer-those who get a normal dose of chemotherapy-suffer from cognitive impairment after the treatments. 30% of women suffering from breast cancer who get a higher dose of chemotherapy have similar problems two years after the treatment too. Chemotherapeutic agents can also harm the mature neurons, but the most significant harm they do is the destruction of brain stem cells. Among the symptoms cancer traction difficulty, mental flexibility’s injury, the deceleration of speed of information processing and the confusion of the functions visual memory and motor are mentioned. Those who received chemotherapy in their childhood and survived for a long period of time, the probability of the occurrence of depression increased depending on the intensity of the chemotherapy.
The irradiation of the head can cause serious brain damage. High dose irradiation can harm the mature neurons by causing serious structural and functional abnormality. Low doses of irradiation can hurt the hippocampus’ dividing the ‘dormant’ stem cells which are everywhere in the brain which activate if a part of the brain is injured. In the case of children it can cause serious malformations which manifest in learning difficulties, slowness, remembrance and understanding problems, concentration difficulties and the decrease in IQ. There is a bacterium (streptococcus pneumonia) which harms the dividing stem cells in the hippocampus by causing meningitis. It’s not surprising that this disease can cause mental disorders similar to the chemo-and radiotherapy’s: remembrance, learning problems, the slowness of thinking, depression, the harming of verbal skills, absence of concentration and hyperactivity. For example lithium and intranasal FGF-2 can give potential protection against the radiation. We reported the last one’s possible anticancer effect in our previous news. It was stated about a polysaccharide type of agent that is able to protect the neurons and fosters the differentiation of the brain’s stem cells which can be linked with the spinal cords blood-forming function’s and strengthening. The methods above can be suitable for the additional therapy of the brain-damaging consequences of the bacterial meningitis. The clinical usage of the intranasal NGF and FGF-18 is considerable: we will report the brain effects of these two neurotropic factors.
Author: Gábor Varga, drug expert
