VASOSPASM. The OSMOTIC PRESSURE HYPOTHESIS.
This hypothesis is based on two things. All of the evidence points to it and 2. Things don't just happen as the neurologist suggests. Like all of my stuff it is based on my research and is, as far as I know, unique as to a valid EXPLANATION of the vasospasm. It is written more for the MD or researcher as a way of VALIDATING my overall hypothesis.
The migrainer might start to experience symptoms of an impending migraine in a couple of days prior to the attack. I'd suggest a series of reactive hypoglycaemia of ever shortening duration as being responsible here. The migrainer wakes up with a sugar craving and is in ketosis, perhaps. Has a sugary breakfast or just a cup of coffee with 2 or 3 teaspoons of sugar in it. But not necessarily so as the person suffering reactive hyper hypoglycaemia seems to become increasingly sensitive to sugar over time, sometimes exquisitely so. Perhaps it's the caffeine. (I'm just thinking out loud). Within a couple of hours the craving returns. Then the same again but sooner as the swings get bigger, finally a migraine. FEAR of an impending migraine as early symptoms appear obviously exacerbates this vicious cycle, worsening symptoms more fear and vicky verka. Finally up goes the BG to an astronomical high and begins to plunge rapidly.
OSMOSIS and the VASOSPASM..
We can divide tissue up into 3 basic osmotic compartments, intervascular, interstitial or between tissue cells, and intercellular. The intervascular department is a bit different as it contains albumin made by the liver. Referred to as a colloid albumin transports a range of different molecules on different charged sites and exerts a lot of osmotic pressure. With liver failure, as with cirrhosis, albumin production drops and fluid increasing leaks out of the blood vessels into the interstitial spaces
A range of ions and polar molecules exert osmotic pressure in solution. These obviously include some whole proteins. Whilst the concentration of the different ions is different between the inside of a cell and the outside, e.g. more sodium outside and more potassium inside, as is necessary to achieve an electrical gradient across the plasma membrane, osmotic pressure is balanced between compartments. If it were not so the compartment with greatest pressure would obviously swell up and burst or just leak badly. A range of cell plasma membrane pumps pump some things in and some things out, some like the sodium potassium pump pumps sodium out and potassium in whilst potassium gradually leaks out by passive diffusion. There is also a pH gradient across the membrane, for instance when red blood cells exchange oxygen for carbon dioxide there is a pH swap on which, what becomes their carbhaemoglobin, a site which ionically binds sodium ions swaps this for a hydrogen ion whilst bicarbonate ions in the cell are exchanged for chloride ions outside the cell. You could say that ionised sodium bicarbonate is exchanged across the membrane for ionised hydrochloric acid when oxygen is off loaded and carbon dioxide is taken onboard. Alkaline oxyhaemoglobin become acidic carbhaemoglobin. Hydrogen ions and chloride ions diffuse into the cell in exchange for sodium and bicarbonate ions which diffuse out, and of course the opposite takes place in the lungs. All well and good. Does that mean that venous blood is more alkaline than arterial blood? From memory not so as free carbonic acid makes venous blood more acidic. Normal arterial blood has a pH of 7.4, however, with very severe metabolic acidosis it can fall to life threatening 6.8. The patient is breathing very heavily as the body to get rid of excess carbon dioxide as it forms carbonic acid in solution
Glucose, being a polar molecule, also exerts osmotic pressure and as long as blood glucose regulation is performing properly, then everything has evolved to be in balance. However, lets say that the BG level shoots up 300% in a half hour. Neurons in the brain do not store glucose as glycogen and thus have no insulin receptors on them. Glucose enters neurons by passive diffusion to be immediately metabolised.. So how does the brain control how much glucose enters neurons to match their fluctuating metabolic rate? The brain controls the ENTIRE BG regulatory system TO SUIT ITSELF, modulating pancreas, adrenals, liver etc. with parasympathetic and sympathetic signals, modulating blood vessels etc. etc. Thus brain cells are bathed in the precise glucose concentration needed to suit their immediate metabolic demands. Localised areas of the brain control blood vessels to match the degree of localised metabolism. Many neurotransmitter (if not all) are also prostaglandin activators,
With reactive hypoglycaemia the brain LOSES CONTROL. So up shoots the BG in the fluid bathing the neuron and because it has no control over it's ingress it turns on an emergency pathway call a Polyol Pathway (multiple alcohol). The idea is to get the glucose in the cell out of solution as quickly as possible. So first it's converted to sorbitol then to fructose and because fructose precipitates out at a lower concentration than glucose, fructose crystals begin to form in the cytoplasm.. However, unlike glycogen which is aosmotic (doesn't exert osmotic pressure) fructose does and when the BG outside the neuron begins to plummet precipitously the fructose crystals begin to pull a lot of water into the cell. The entire brain swells in a migraine and this is why. A lot of neurons may be permanently damaged. Unable to repair themselves, and unable to turn on apoptosis, they 'inappropriately' express MHC2(?) receptors, thereby behaving like an APC (antigen presentation cell) and so initiate an immune response against themselves. Auto immune 'attack' maybe. Just a hunch!!
In a desperate attempt to limit the osmotic pressure imbalance and limit the damage the brain must secrete a vasoconstrictor in blood vessels supplying it, even though this constriction will worsen the already severe hypoglycaemia and create hypoxia just at a time when cells need both glucose and oxygen to make ATP to DRIVE THE BAIL OUT PUMPS. As noradrenalin is a constrictor in blood vessels in which adrenalin is a dilator, then I'd nominate it, but not coming from the adrenals, but from the brain itself in order to limit this constriction to just these blood vessels alone. This is purely a hypothesis and the reason I believe that it does this is to retain as much electrolyte, calcium, sodium etc. in the interstitial fluid to compensate for the loss of glucose. It is a desperate attempt to balance one crisis against another. If the migrainer is very frightened and is considering the possibility of a stoke, even death, then the extra neural activity of fear (the brain on average uses 40% of the body's glucose) further exacerbates the overall problem. Fear also creates hypersuggestability, or the ability to imagine even worse consequences, Hellfire, thus even more fear ad infinitum. Blacking out would be protective against this runaway fear and that is why, I believe, an epileptic blacks out before an attack.
Finally the hypoxia added to the hypoglycaemia becomes the predominant problem and flood of vasodilator is released and these blood vessels massively dilate instead. One important dilator is ADP which builds up in cells unable to phosphorylate it to ATP and is released from these cells. Bradikinin sensitises pain receptors so it is possibly involved as well. MIIIIIIIGRAINE!!!!!
Now consider other factors which must contribute to the mental confusion as the blood sugar falls. A huge imbalance in the concentration of ions across the plasma membranes of a neuron, must drastically alter it's depolarisation/repolarisation when it fires, thereby altering the firing potential of it's synapses, along with the drastic shift in pH gradient also having a negative affect.
Next, the gyrations of the rest of the soma. Noddy (Paul Hill)