Moving platform posturography, also called computerized dynamic posturography (CDP), or posturography for short, is a method of quantifying balance (although the definition of balance can be tricky). It is most applicable in situations where balance needs to be followed quantitatively, to determine whether a disorder is getting better or worse, or the response to treatment.
The commercial device produces a "sensory analysis" graph, which is an attempt by the computer running the CDP to suggest whether there is a "somatosensory" deficit (SOM), a Visual deficit (VIS), a vestibular deficit (VEST), or a difficult to figure out deficit, called a "PREF".
Generally speaking, there are almost NEVER patients seen with the SOM deficit. There are a moderate number of people with the "VIS" pattern, usually somewhat sensible. There are a gigantic number of people with the VES pattern, which includes people with no vestibular issue at all -- i.e. many false positives (see below). There are rarely people with very well documented vestibular loss, (see below again), who score normally on the "VES" sensory test (i.e. a false negative).
The PREF pattern is difficult to figure out. It doesn't correspond to any disease, and clinically has no use at all.
Posturography is insensitive to vestibular disorders, and normal posturography should not be considered indicative of normal vestibular function (Di Fabio, 1995). The author has had instances in which there is a severe disturbance of caloric testing and rotatory chair testing, accompanied by a normal CDP. CDP is therefore not an adequate test for vestibular disturbance, by itself.
In addition to the false negative problem (lack of sensitivity), CDP also has false positives - -it suggests that there is a vestibular problem when none exists.
The "vestibular" pattern on CDP is actually not specific for vestibular disorders. This is particularly obvious these days when we have newer tests for vestibular (such as VHIT), that can be perfect even when the CDP is "vestibular". The graph above shows a "vestibular" pattern in a man who had a perfect "VHIT" test, showing he has no vestibular loss at all, at l.
The author has had instances in which there is a severe disturbance of caloric testing and rotatory chair testing, accompanied by a normal CDP. CDP is therefore not an adequate test for vestibular disturbance, by itself.
The case above was of an older lady with gentamicin ototoxicity as well as a "dead" right ear, well documented. Rotatory chair testing was very abnormal, and her "DIE" test dropped 5 lines showing that she has oscillopsia. She also has cataracts.
As shown above, this very well documented individual with vestibular damage, had an entirely normal vestibular pattern on her sensory analysis, showing a false negative.