8(a)To minimise the effects of the tumour on the brain; in particular, to reduce the 'mass effect' it causes, and to reduce the prospect of seizures: overview
These (reducing swelling and preventing seizures) are two matters generally arising in conversation with doctors and nurses as separate subjects, but most usefully seen as part of the same cloth.
Swelling and pressure in a confined space - destructive:
Central to understanding the management of brain tumours is the fact that the brain is a confined space inside the skull - this 'intracranial' space is not flexible as, say, the stomach is, when there is a growth developing. Anything strange produced in the cranium is hard to dispose of, to remove from the brain. Elsewhere in the body this there are efficient systems for removing waste materials, but behind the blood-brain barrier it is more difficult. The accumulation of unwanted stuff in the intracranial space is the source of pressure; pressure causes inflammation, weeping of tissue and swelling. This all makes for a self-reinforcing destructive pressure on the healthy brain. So a brain tumour does its destructive work essentially by crushing the brain.
The metabolism of tumours involves the production of large amounts of lactic acid. So it's not just the mass of the tumour at work, this fluid product increases pressure.
The killing of tumour cells, by radiation or by chemicals, produces a mass of inflammation which adds to the cycle of inflammation, swelling, weeping, pressure buildup. The 'mass effect'.
This has an important consequence in limiting the use of these anti-tumour treatments to times when there is not a burden of pre-existing pressure on the brain. What that means in practice is that there is a logic of carrying out an operation before the radiation and chemotherapy, to remove material, to ease pressure, to reduce to a minimum that amount of tumour that has to be treated by radiation and/or chemotherapy… bearing in mind that an operation itself is a great annoyance and irritant to brain tissue, and will cause inflammation. Note that often at diagnosis, scans will show lots of pressure buildup and some days of treatment with dexamethasone (see below) may be needed to reduce the pressure and make the operation safer.
Brain Message systems, electrical storms:
The activity of nerve cells, including brain cells, involves the transmission of tiny electrical charges across gaps — synapses —between nerve cells. There are also neurotransmitter chemicals involved, substances created to carry the signals, then broken down (reuptake) after the job is done. These are sensitive and delicate processes, of which medical science still has only modest understanding.
If these electrical and chemical processes go wrong, there may be seizure, as in epilepsy. There are many different types of seizure, defined by different characteristics. The person suffering the seizure may or may not be aware of the seizure, depending on how the areas of the brain involved in consciousness are involved and overwhelmed.
A person with a brain tumour may experience seizure as a first symptom; or may experience seizure for the first time after an operation, or with later disease progression, or not at all. The prospect of seizure arises with the way the tumour pushes the brain around, squeezes it, or the way the brain is interfered with in an operation, or the way bits of necrosis, dead tumour cells, may move and impact on brain cells. As an analogy, consider a force pushing electric wires close to each other, consider rough cutting through a mass of wires which then have to self-repair.
In the management of brain tumour, drugs [a] to control swelling and [b] to limit or prevent seizure are very important. They tend to be prescribed and discussed with patients separately.
My concern in this overview is to draw attention to this interlinking — the drug to control swelling, while effective, may prevent the situation with seizure potential from arising; the anti-seizure medicine comes at the problem from the other direction, dampening down the chemical base for seizure.
Taking the one kind of drug does not remove the need for the other, if medically prescribed. However, weaning off the drug used to control swelling and/or growth of the tumour increase the risk of seizure. If seizure then strikes, it is easy to say "why has my anti-seizure medication failed?" when that may be an unfair test of the latter drug if swelling and pressure are elevated. Appropriate immediate remedy includes also review of the anti-swelling (anti-inflammatory) medication. There is a range of anti-seizure medication options and these may need to be changed along the way. There is no clear replacement among drugs for dexamethasone as anti-inflammatory.