Nausea and vomiting commonly accompany vertigo. People vary in how sensitive they are to motion. Some vomit with even mild dizziness, and others can experience violent vertigo with only mild nausea. If you can see the environment spinning, and it continues for more than a few minutes, nausea will usually begin to build. Vomiting can be set off by several different bodily systems (food poisoning in the stomach and intestines, for example) and it is controlled by the brain with a very complex set of subsystems.
The vestibular system is interconnected with the reticular formation, part of the brainstem that coordinates and controls key centers for consciousness. This formation includes the reticular activating system, a network in the brain that helps in arousal and awakening. It is important that a person awaken when the head is suddenly moved, because it can indicate an impending fall. When you abruptly jerk your head upright after starting to nod off, or when someone shakes you to help wake you up, you are using this system.
The vomiting center of the brain is located within this network, partly so that you will awaken if you begin to vomit while drowsy or asleep. Sleeping through vomiting is a bad idea—it results in choking. It’s key that you avoid this fate, so the brain is set up to prevent this. Unfortunately, this means that there is a connection between the vomiting center and the vestibular system because both of them feed through the reticular formation. The physiology of this connection is so complicated that how and why these are connected is still not completely understood.
Medications for motion sickness help to reduce the amount of vestibular stimulation, and so control the nausea. They are usually also helpful when the nausea is due to vertigo from vestibular disorders. Vestibular suppressants such as meclizine, diphenhydramine, tranquilizers or scopolamine are particularly effective.
Our next blog will discuss the problem of repeated dizzy spells.