She worked in AC all day. So why did her migraines get worse every afternoon?

How heat affects the brain, even indoors

The fact is, the impact of a heat wave does not depend on whether the patient is sitting in direct sun rays or comfortably sitting at home. Heat often accompanies drops in barometric or atmospheric pressure. And such changes become a physical trigger for the nervous brain. Barometric pressure changes, particularly drops preceding storms, are common migraine triggers, causing headaches by creating pressure differences in the sinuses and inner ear. These affect over a third of migraine patients.

Moreover, the heat triggers vasodilation, which means blood vessels widen in an effort by the body to try to lower its core temperature. This dilation occurs more frequently among those susceptible to migraines when it takes place in the blood vessels located around the brain, putting pressure on the brain’s sensitive nerves to launch an attack. Regardless of whether one is resting in a cooled environment, the body might still be undergoing the physical after effects of walking to the vehicle or even trying to adjust to the change in atmosphere despite the presence of the air conditioning.

The summer surge: New cases or attacks?

A combination of both, although more likely the latter. When summer reaches its peak in Mumbai, the number of “secondary” headaches in patients, who normally do not suffer from migraines due to heat exhaustion or dehydration, goes up significantly. But the major problem lies within the migraine patients, where the number of attacks goes up from two monthly to around eight or ten. Heat reduces the “migraine threshold.” In simple terms, it would be like a cup of hot liquid almost spilling due to being filled up 90 per cent of the time. The body is stressed out due to the strain of maintaining internal temperature, making the nervous system hyper-reactive to any stimulus.

The “invisible” summer triggers

• Though it is obvious that one must avoid the intense heat during noon, it is some of the other less considered triggers that contribute to summer migraines. One of them is what we call shower shock. It might be tempting to hop into a cold shower right after stepping out of the hot weather, but this sudden exposure to contrasting temperatures may trigger a “cold-stimulus headache” that will often lead to a migraine.
• It should be understood that air conditioners do not only reduce temperatures, they also reduce humidity levels. Due to the lack of visible sweat on the skin, dehydration, another trigger, is usually overlooked in such an environment.
• Caffeine is a common beverage consumed by people on hot days as it provides an immediate jolt of energy. But it is a diuretic. The addition of this to sweating during commuting leads to dehydration.
• Heat is often associated with a lack of appetite, which can be disastrous when coupled with low blood sugar.

The changes we made for our patient

The young professional stopped using the tight head wrap and used an umbrella instead because this would help her air out her head during her walks. Second, she reduced two cups of tea with salty chaas (buttermilk) or fresh coconut water to help her replenish her electrolytes. Lastly, she ensured that she ate a nutritious snack with proteins before going to work.

Not only do you need to stay indoors as much as you can, you have to stabilise your body, drink fluids and understand that your brain cannot handle the shifting thermometer.

(Dr Gopal is Additional Director of Internal Medicine at Sir H.N. Reliance Foundation Hospital, Mumbai)