Having hydrops is like walking a tightrope. The ear is very vulnerable, on the edge of losing blood flow. Slight changes, like eating a salty meal (Thanksgiving is notorious for this!) can put you at risk. But hydrops alone doesn’t make the spell happen. That requires a decrease in blood flow in the brain itself. All the blood that courses through the inner ear comes in and exits through vessels in the brain, so if the brain blood flow is low, that adds to the problem in the inner ear.
It’s the pressure difference in the blood vessels, with higher pressure in the arteries and lower pressures in the veins, that matters. Low blood flow can come from vasospasm, a shrinkage of the arteries due to contraction of muscle in their walls, or from a back-up of pressure from compression of the veins in the skull. In either case, blood flow is reduced. If the ear is already compromised by hydrops, an episode of vasospasm or venous blockage can cut off flow to the point that the ear is ischemic, lacking the oxygen and sugars needed to survive.
Most of the ear can deal fairly well with low flow and recovers quickly once flow is restored. Press on a fingernail until it gets pale and then let go; it pinks right back up. The nerve endings within the inner ear are different. They don’t recover quickly from very low flow. Once I knelt for two hours in a Japanese tea ceremony. My legs felt like wood, completely numb. Once I stood up, I had spectacular pins-and-needles for several minutes. Yowza! I’d cut off some of the blood flow to the nerve while kneeling, and then they became irritable after flow was restored.
When the nerves in the ear have low flow, they stop working. This causes all the signs of a Meniere attack: your hearing goes down, especially in the low tones; you hear a very loud roaring sound in the bad ear, and the room begins to spin. If flow is restored within a few minutes, the spell will end. However, if low flow continues on for several minutes, the nerves go past the point of no return, and even when flow is restored, they will not function normally. The process is called excitotoxicity; basically, the nerves leak toxins like excess calcium while they are shut down, and then are damaged as it floods back in as blood flow is restored. Once this process starts it cannot be stopped and the nerves have to restore themselves on their own, which can take a few hours.
When the nerve endings in the ear have stopped working, the hearing loss, tinnitus, and vertigo will continue until they wake back up. The best thing to do while waiting is to find a position that is comfortable: lying with the head propped up, turning your head until you find a position that reduces the speed of the spinning, and moving your eyes until you find a direction that slows the spinning. It’s very boring, but you have to hold the position until the nerve endings recover. Moving the head quickly can set off vomiting, so you want to lie very still.
After a few hours the nerves will reawaken, and you will notice that the spinning is slowing down or even reversing direction, the roaring sound is less, and the hearing is starting to return. For the next few hours, putting your head upside down will lower the blood flow by increasing pressure in the veins, and the spell will start up again. That’s the sign that you’re still in the recovery phase.
After the spell is completely over, there may be some residual damage to some of the nerve endings for hearing or balance. It’s spotty, and might not show up on testing right away, but over the years it gradually accumulates. It is worth trying to prevent the spells and slow down the damage. I’ll discuss some of the treatments in the next post.