Even if there is a treatment that has adverse effects, people may decide that the adverse effects are worth the pain relief. But to make that evaluation the side effects need to be known. So far side effects for TMS are unknown, and the mechanism(s) by which TMS works are unknown too.

Conventional treatments for migraine have been around a long time and have a known side effect profile. New therapies do have new therapeutic potentials, but they also have new side effect potentials.

An analogy might be something like anaphylaxis. When you have a very strong immune system stimulation, like bacteria in the blood stream, you have a very strong immune system response, sometimes anaphylaxis which can be lethal. Preventing lethal anaphylaxis is important, but having an intact immune system is important too. High dose immunosuppressive drugs might be prophylactic for anaphylaxis, but too much suppression makes you hyper-susceptible to infections.

A lot of physiology is regulated by feedback mechanisms, where one stimulus generates an adverse effect and that adverse effect stimulates an even larger protective effect. There is some thought that this is how anti-carcinogens in food work, the compound causes metabolic or oxidative stress, and then protective mechanisms hyper-respond and overcompensate for the stress. That is how exercise works, your muscle is unable to do the task that you call it to do, so your body makes the muscle bigger. If you stopped the overload signal from the muscle so overexertion didn’t hurt, would physiology make the muscle bigger? It might not.

If migraine is ischemic preconditioning, and one of the effects of a migraine is to cause vascular remodeling that increases blood supply to the ischemic tissue, then if the migraine is interrupted before the signal to generate vascular remodeling is generated, a signal might not be generated and vascular remodeling would not happen. That might (note the speculation) have adverse effects. That is not to say that migraine should not be treated, just that it should be treated in ways that preserve the signaling that increases the blood supply.

As we’re a work in progress, not a finished product, it could be that migraine is a side effect of another feature which is selected for, in the same way that sickle cell anemia is a side effect of higher resistance to malaria.

The question is whether it has individual benefits and shouldn’t be treated, or whether it’s only a benefit when seen in the context of the entire gene pool, in which case treating individuals is still a good idea.

I go into great detail on my blog how the ability to support an autism phenotype might have been selected for.

Bonding to other humans in love relationships; same gender and opposite gender; certainly has advantages and certainly has been selected for. Those advantages depend on individual circumstances and humans exhibit a continuum of behaviors. Complex traits with complex genetics that exhibit a continuum of behaviors in the phenotype have been selected for. Specific points on the phenotype continuum might not be advantageous (depending on the circumstances), but the ability of a genotype to produce a phenotype with a continuum of behaviors certainly must have been selected for.

Brown eyes do exhibit greater resistance to glare and probably reduced UV damage. There does seem to be a reduced incidence of cataracts in people with dark eyes. Brown eyes are more common in regions with greater sunlight.

The point I am trying to make is not that migraine has some advantages and that stopping migraines will cause problems. I don’t think that is the case. What I am trying to say is that migraine is a complex process, a process which is not fully understood. A treatment that interrupts that process via non-physiological methods and stops pain symptoms may cause harm disproportionate to the harm of the normal progression. It might be treating the symptoms vs. treating the underlying pathology.

This is a cartoonish example, but if an individual has a broken leg and is in a lot of pain, treating the pain with opiates doesn’t fix the problem, the leg is still broken.

If the pain from light sensitivity during migraine is a “feature”, blocking that pain might cause adverse effects. For example, if pain is triggered because there is a disruption of automatic regulation of neuronal activity in the visual cortex, matching metabolic capacity to neuronal activation, reducing stimulation until the automatic regulation is restored might be a mechanism by which the pain is adaptive. If the pain is blocked and the automatic regulation not restored, cells may become overloaded and forced into excitotoxic apoptosis (which is painless).

Right now, the mechanism by which TMS has effects is not known. Without knowing the mechanism and without having a lot of experience that the practice does not have adverse effects, whether there are adverse effects is unknown. There might be no adverse effects, but until it is looked at pretty carefully that is unknown.

There are many possible reasons for a trait to persist despite it not being specifically selected for, and this depends on the specific situation. In general, here are a few reasons: 1. The gene(s) involved in the trait are genetically linked to other genes that are advantageous 2. The trait involves many genes, and some of these genes are advantageous for other reasons (for example with migraines perhaps some of the genes involve may be beneficial for normal physiolgy, but contribute to migraines when other genes are present) 3. The trait is a by product of the design of normal anatomy/physiology (i.e it may be a limitation of design), etc…

“Migraine is not a simple trait”
– This is precisely why the argument that is explicitly selected for is harder to demonstrate. Why it is so common may be related to the fact that we all have the same basic physiology. The “in sync-ness” of migraine and seizure is a by product of the basic physiology. Perhaps we are all capable of migraines, but for some the threshold to migraine is lower. With many genes involved we get to the issue I brought up in #2 above. Some of the genes involved may be beneficial in most instances, but becomes harmful in the presence of other genes that contribute to migraines.

No disrespect, but I just want to point out the fallacy that because a trait exists and may be even common, that it is explcitly selected for.

Ischemic preconditioning is not speculation, that is extremely well known. Every tissue compartment exhibits it.

If migraine is purely pathology, then why is it pretty common? Why do so many individuals have “the same” pathology? If the physiology that leads to migraine is only detrimental, then why do so many people have it? It seems to me that the idea that the migraine trait became common in the population even as migraine had only detrimental effects is much less likely than the idea that the physiology of migraine may have some protective and/or beneficial features under some circumstances.

Migraine is not a simple trait. It is a complex trait requiring the concerted action of many different physiological sub-systems. Migraine requires the action of entire brain volumes acting together and “in sync”. That requires communication between those different tissue compartments and the propagation of the physiological state associated with migraine from one region to another.

TMS requires a pulsed magnetic field, usuall a few kJ pulse delivered in ~100 microseconds. That is a few tens of megawatts. Pulsed equipment can deliver that and still be relatively small. For comparison, a portable Automatic External Defibrillator uses about 100 to 200 J per pulse, about 1/10 as much and over a longer time frame, maybe 10 milliseconds, about 0.01 megawatt. To a first order, a portable TMS would need to be about 10x larger in size and weight than an AED.

A lot of speculation upon speculation. Although it is natural to look for an evolutionary advantage to migraines, it could just be a pathology of the normal physiology of our nervous systems. Why does it have to have some utility or evolutionary advantage? Migraines themselves can be debilitating, and I could see it being a huge disadvantage for some, particularly in the past. Natural selection does not eliminate all things that don’t have a survival benefit. By the same reasoning, what utility do seizures have?

Cells require ATP to stay alive. If the ATP is depleted, the cells die. That is the mechanism for excitoxic cell death, metabolic stress due to ATP depletion which triggers apoptosis. Slow ATP depletion triggers apoptosis (when there is enough ATP remaining to go through the apoptosis subroutine), rapid depletion triggers necrosis (when there isn’t enough ATP to do apoptosis).

There could also be problems in mitochondrial regulation that wouldn’t show up until it is too late. I talk about some of those in respect to the use of the “magic helmet” (high intensity pulsed NIR on the brain) to treat Alzheimer’s. I discuss some of the details of that in my blog post.

http://daedalus2u.blogspot.com/2008/06/more-on-magic-light-helmet-for.html

In the context of migraine, I think it has been pretty well established that migraine is a state of ischemic preconditioning and is either very similar or identical to spreading depression. That is a “normal” physiological state, normal in the sense that there are natural pathways that trigger the effects, they go through a regulated progression, with the key concept being that the process is under physiological regulation. Ischemic preconditioning is a stress response from deep evolutionary time, a response for cells to survive ischemia and ATP depletion. What happens when you whack that regulated process with TMS? Since the normal process is not well understood, perturbations to that normal process by non-physiological things like TMS are even less understood. I think it is unlikely that whacking brain tissue undergoing spreading depression with TMS will suddenly resolve the ischemia or ATP depletion or what ever else that triggered it in a completely benign manner.

TMS is associated with reductions in blood flow (depending on how it is done). To me, that implies a reduction in nitric oxide levels. Normally neuronal activation is associated with increases in NO, that is what causes the vasodilatation observed in fMRI. Migraine is not associated with vasodilatation or increases in blood flow (understanding this is complicated because the main effect of ischemic preconditioning is reductions in O2 consumption, with unchanged perfusion, O2 levels would go up. If O2 levels don’t change during ischemic preconditioning, then perfusion has gone down, there are fMRI BOLD measurements indicating increases in O2 during migraine, I interpret these as being due to reduced O2 consumption, most authors interpret them as increased blood flow (the usual explanation in non-migraine)).

Migraine all by itself may be causing neuronal damage. I suspect that might be a “feature”, to prune the brain and reduce the metabolic load. If the brain doesn’t have sufficient metabolic resources to sustain itself, excitotoxic cell death might be a safety measure to prune the excess. An evolved survival feature that may protect from a future seizure that could be lethal in the presence of predators, but which accelerated dementia a little bit. In the wild, dementia at age 60 would have essentially no consequences because few lived that long. Now it has serious consequences.

The peak fields with TMS are quite strong, on the order of Tesla, the same order as the fields used in MRI, but last only a hundred microseconds or so. MRI fields are static. The MRI fields do not induce voltages inside the brain.