A number of questions on the survey related to activities likely to change "internal" pressures of the body, specifically that of the cerebrospinal fluid (CSF). The fluid spaces of the inner ear are connected to the CSF by a small duct called the cochlear aqueduct. In most humans, this duct is believed to be patent, so that pressure changes of the CSF are transmitted directly to the ear. This raises the question of whether such pressure changes of the ear change its function in any way and thereby affect the symptoms. The normal ear appears insensitive to such changes.
The rationale for these questions was based on the fact that when you lie down, the CSF pressure in the head increases. Similarly, the other activities which tense the abdominal muscles, including coughing and sneezing and lifting all cause increases in CSF pressure. In the graph above, it is notable that these changes are more commonly associated with the symptoms getting worse, than with symptoms getting better (as indicated by the fact there is a lot more red in the above graphs than there is green). Except for the posture changes, which I will discuss below, these activities which tense the abdominal muscles mostly have no effect, but in individuals where there is an effect it appears more commonly to make the symptoms worse.
The response to posture changes is more complex, because this includes both directions, both lying down and standing up. We therefore tried to separate out which changes were caused by standing up or lying down with the following questions.
Questions posed : If postural changes affected your symptoms:
1) Did symptoms get worse when (Lying down) (Standing up) or with (Any Posture change)
2) Did symptoms get better when (Lying down) (Standing up) or with (Any Posture change)
Of the 56 respondents who answered these questions (the ones who were sensitive to posture changes in the top graph) the majority felt better lying down and the majority felt worse when standing. However, considering that you would expect most people with vertigo to want to lie down, what is surpising are the numbers (25%) who felt WORSE lying down and the 15% who felt BETTER standing up. This could be partly related to CSF pressure changes if CSF pressure increases tend to make symptoms worse as indicated above, although other factors are likely involved as well.